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ALBERT R. MANN
LIBRARY

NEw York STATE COLLEGES
OF
AGRICULTURE AND HoME ECONOMICS

CORNELL UNIVERSITY

 
ornell University Libra’

“aN
tate of Gonnecticut
PUBLIC DOCUMENT No. 47

 

 

State Geological and Natural
History Survey

COMMISSIONERS
SIMEON EBEN BALDWIN, Governor of Connecticut (Chairman)
ARTHUR TWINING HADLEY, President of Yale University
WILLIAM ARNOLD SHANKLIN, President of Wesleyan University
FLAVEL SWEETEN LUTHER, President of Trinity College (Secretary)
CHARLES LEwIS BEACH, President of Connecticut Agricultural College

SUPERINTENDENT
WILLIAM NORTH RICE

‘

BULLETIN No. 19

 

HARTFORD
i Printed for the State Geological and Natural History Survey
1912
.

PuBLICATION AUTHORIZED BY THE
BoarpD oF CONTROL

The Case, Lockwood & Brainard Co., Hartford, Conn.
Echinoderms of Connecticut

By «a
WESLEY ROSWELL COE, Ph.D.
Professor of Biology, Sheffield Scientific School
of
Yale University

 

HARTFORD

Printed for the State Geological and Natural History Survey
IgI2 ’
Preface

In the preparation of this report on the Echinoderms
to be found in that part of Long Island Sound which borders
the Connecticut coast line the writer has been influenced by
two incentives: first, to aid in arousing an interest in the
study of a most remarkable group of animals of common
occurrence; and, second, to aid in the dissemination of use-
ful knowledge of the structure and habits of the starfish — the
deadliest of foes to the oyster, which constitutes one of the
state’s valuable natural resources, and with which a large
and important industry is connected. With these ends in
view, an attempt has been made to furnish such adequate
illustrations of each of the species of Echinoderms found in
the waters of the state as will facilitate their easy recognition,
while the economic importance of the starfish has been as
fully investigated as the conditions would permit.

Free use has been made of the many excellent treatises
on the animals concerned; and grateful acknowledgment is
made to Professor A. E. Verrill, of Yale University, for the
use of specimens and photographs; to Professor Hubert
Lyman Clark, of the Museum of Comparative Zodlogy, Har-
vard University, for the use of a number of the photographs
which illustrate his excellent report on the Echinoderms of
the Woods Hole region; and to Mr. Davenport Hooker and
Mr. Stanley C. Ball, for assistance in the preparation of the
illustrations.

In the bibliography at the end of the report will be
found a list of some of the most useful publications on our
native species of Echinoderms, including those on the
economic importance of the starfish.
Contents

Introduction. : é : : é ; . I
Classification . 2 , 3 : : ; . 33
Asteroidea < ‘ : : ‘ j . 19
External Structure ‘ : ‘ ‘ 3 . 20
Internal Structure ‘ s : ‘ ; a 325
Habits ‘i ‘ 3 : ; y ‘ . 28
Food ‘ P ‘ : : ‘ . 29
Natural Enemies . : ; @ (32
Damage to Oysters aad, Other Mollusks . é - 33
Rate of Growth . 5 : ‘ é : . 40
Migration . é = 43
Variation in Number aa Arrangement of Rays : 2, O43
Regeneration j - : 7 , : » 45
Reproduction ? A : : 3 : . 48
Development 4 , : ‘ ‘ 3 «. $2
Key to Species : : , : : . 58
Asterias forbesi , 2 ‘ : A . 59
Asterias vulgaris. ; ‘ ; 3 . Or
Asterias tenera : ‘i é ; : . 63
Henricia sanguinolenta ‘ é ‘ ‘ . 65
Ophiuroidea. : ‘ : : ; ; . 67
Structure . , ‘ spe : ; ; . 68
Habits : : é . j . 73
Food : ‘ . : ‘ : - 75
Reproduction ; ; ‘ ‘ ‘ . 76
Development 2 3 = 5 : : . 977
Key to Species. ; : 3 é : - 79
Ophiura brevispina . i ‘ ‘ ‘ . 79
Ophiopholis aculeata ; ‘ ; é . 80
Amphipholis squamata . 3 ; : . 81
Amphioplus abditus ; : : . . 82
Amphioplus macilentus . . ; ; . 84
Echinoidea : : ‘ ; ‘ : . . 85
Structure . 2 ‘ : . : ; . 85
Habits si ; ‘ . : ‘ ‘ .
Reproduction . ; : ; 3 : . 100

Development ‘ ‘ ‘ , E ‘ . 100
8 CONNECTICUT GEOL. AND NAT. HIST. SURVEY.

PAGE
Echinoidea— Continued
‘ 106
Key to Species ‘
Arbacia punctulata . ae
Strongylocentrotus debbachionsts. =
Echinarachnius parma aw
Mellita pentapora- pais
Holothuroidea ; aad
Structure . ‘ . . . 3 eS
Habits and Food| i : : j . eee
Autotomy . . » 425
Regeneration 126
Reproduction and Development . . 128
Key to Species. i ‘ ‘ . eo £29
Cucumaria pulcherrima ‘ ; 5 130
Thyone briareus ‘ ‘ ‘ : . - 133
Thyone unisemita . ‘ 5 P . 135
Thyone scabra ? : . . 136
Synapta inherens . 4 ‘ ; : 138
Synapta roseola ‘ , : : ‘ - 4!

Bibliography . ‘ 3 ‘ , : . 144
I.

Il.
Tl.
IV.

Vv.
VIL

VII.
VIII.

IX.

X.
XI.
XI.

XIII.
XIV.
XV.
XVI.
XVII.
XVIII.

XIX.

XX.
XXI.

XXII.
XXIII.
XXIV.

XXV.
XXVI.
XXVII.
XXVIII.
XXIX.

XXX,
XXXI._
XXXII.

List of Illustrations
PLATES

FACING PAGE

Starfishes and Ophiuran, Astertas forbesi, Henricia
sanguinolenta, and Ophiura brevispina

Skeleton of Starfish, Asterias forbest

Aboral surface of Starfish, Asterias forbest

Oral surface of Starfish, Asterias forbest

Anatomy of Starfish, Asterias vulgaris

Rate of growth of Starfish, Asterias forbest

Variation, Asterias forbes? . ‘ é

Asterias forbesi and Asterias vulgarts

Asterias vulgaris .

Asterias tenera

Flenricia sanguinolenta

Variation, Ophiopholis aculeata . ‘

Skeleton of Ophiuran, Ophiopholis aculeata

Skeleton of Ophiuran, Ophiura brevispina

Ophiura brevispina ; :

Ophiopholis aculeata

Amphipholis squamata

Amphioplus abditus :

Amphioplus abditus and Amphioplus macilentus

Sea-urchin, Arbacia punctulata . :

Skeleton of Sea-urchin, Strongylocentrotus dré-
bachiensis

Anatomy of Sea-urchin, Arbacin punctulata

Skeleton of Disk-urchin, Zchinarachnius parma

Anatomy of Disk-urchins, Me/lita pe and
Lichinarachnius parma : i :

Arbacia punctulata ‘

Strongylocentrotus drobachiensis .

Lichinarachnius parma .

Mellita pentapora

Holothurians, Syzxapta roseola, ' Synapta \ inharens,
and Zhyone briareus . : 7 ‘ :

Anatomy of Holothurian, Thyone ieibeeds

Thyone briareus i S48

Cucumaria pulcherrima, Thyone tnicornite, Thyone
scabra, and Synapta inherens.

13
19
21
22
25
41
43
60
61
63
65
67
68
71
79
80
81
82
84
85

87
89
g2

95
107
108
110
112

114
117
133

136
10

os

SBP SOO SY ON SN

10.

12.
13;
14.
15.
16.
17.
18.

19.

21.
22.
23.
24.
25.
26.
27.
28,

CONNECTICUT GEOL. AND NAT. HIST. SURVEY.
FIGURES IN TEXT

Section of ray of Starfish
Diagram of water-vascular system of Starfish

Comparison of rate of growth of two starfishes under dif-
ferent conditions

Larva of Starfish

Larva of Starfish

Young Starfish shortly after seeping

Young Starfish devouring a mollusk

Pedicellariz of Starfish .

Oral surface of disk of Ophiuran

Diagram of section of arm of Ophiuran

Larva of Ophiuran, Ophiopholis aculeata

Larva of Ophiuran, Ophiura brevispina

Aboral skeleton of Sea-urchin, Arbacia punctulata
Aboral skeleton of Disk-urchin, Echinarachnius parma
Cleavage of egg of Sea-urchin .

Larva of Sea-urchin .
Young Sea-urchin iminediatsly: after seretahnernsitionts
Young Sea-urchin, Arbacia punctulata

Young Disk-urchin, Méellita pentapora

Diagram of section of body of Holothurian

Oral tentacle of Holothurian

Cucumaria pulcherrima .

Plates of Cucumaria pulcherrima

Plates of Cucumaria pulcherrima

Plates of Thyone briareus

Plates of Thyone unisemita

Plates of Zhyone scabra .

Plates of Synapta inherens

Plates of Synapta roseola

vACE
23
27

42
54
54

55
58

70
72
78
78
88
93

101

102

103

104

105

115

120

131
132
1%
136
137
140
143
ECHINODERMS OF CONNECTICUT

INTRODUCTION

Among the natural objects most likely to attract the attention
ef the visitor to the seashore, particularly if the coast be somewhat
rocky, are the five-pointed star-shaped creatures known as star-
fish. These are often found abundantly clinging to the rocks
and seaweeds when the tide is low.

Among the seaweeds below the reach of the tides are some-
what similar animals, which have five slender, wriggling, snake-
like arms, commonly known as serpent stars.

Just below the reach of the low tide also are other related
animals, of rounded form, covered with coarse spines, which are
commonly known as sea-urchins.

And, finally, when digging in the sand between tides, one_may
encounter pink or whitish worm-like animals, without distinct
appendages to the body, but which nevertheless are able to cling
to the hand; and these may belong to the group of animals
known as sea-cucumbers, although our native species have little
resemblance to the vegetable from which they take their popular
name.

These four classes of animals occur abundantly along the
shores of Long Island Sound, and careful search and critical ex-
amination will reveal the fact that there are several species of
each.

All these animals belong to the division of the animal king-
dom known to zodlogists as Echinoderms; for, although the
starfish, sea-urchin, serpent star, and sea-cucumber may seem at
first glance to differ from each other about as widely as any
animals can, yet a careful study of their internal anatomy shows
that all are built upon the same general structural plan. They
furthermore have in general a similar embryology and life history.
Herice the zodlogist and evolutionist believe that they are all
12 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.

related to each other, and have no hesitation in placing them to-
gether in a single group, or phylum, known technically as the
Echinodermata.

These Echinoderms may be distinguished from other animals
by certain well marked characters. As the name implies, the
skin in most forms is provided with calcareous spines which pro-
ject out from all sides of the body. Such spines are wanting
however in the sea-cucumbers. Other calcareous plates are found
in the skin. In most forms such plates unite to make a more or
less complete shell which serves to protect the delicate internal
organs. Most of them have likewise a distinct radial symmetry,
in that similar parts are repeated around the central axis, as
illustrated by the arms of the starfish or serpent star. With few
exceptions they have a well developed water-vascular system,
consisting of a circular canal around the mouth, with radial
branches leading out to the periphery of the body. From the
radial canals numerous branches lead out into the skin in certain
regions of the body, and grow out into delicate tubular or finger-
like projections.

These delicate projections are variously modified in different
parts of the body for the performance of certain special functions.
In all cases they serve as sense organs and as respiratory organs.
If they have no further function they are known as tentacles;
but in many cases they serve also in the locomotion of the body,
and are variously known as tube-feet, sucker-feet, or pedicels.

These animals are found only in salt water, with the exception
of one or more tropical species which are able to live in brackish
water.
 

 

 

 

 

PLATE I. Wigs. 1-3, /fenriva sanguinolenta, Fig, 4,

A sterias Sorbesi, ;
Fig. 5, Ophiura brevispina.

 
No. 19.] ECHINODERMS OF CONNECTICUT. 13

CLASSIFICATION

All the Echinoderms of the world are divided by zodlogists
into two sub-phyla, only one of which, the Eleutherozoa, is repre-
sented in our local fauna.*

The Eleutherozoa are divided into four classes, all of which
have representatives, living in Connecticut waters.

Class 1. Asteroidea: Starfishes—- The body consists of a
central disk which passes without sharp demarcation into five or
more symmetrically arranged arms or rays (Plate I). The large
mouth occupies the center of the disk on the ventral, or oral
surface, while the minute anus is situated opposite, that is, on the
aboral side of the disk. The arms are without joints. A deep
groove on the oral side of each arm is thickly covered with tube-
feet which serve to move the animal from place to place.

In Long Island Sound occur four species of this class, each
of which has five arms. They comprise the common starfish
(Asterias forbesi), the northern starfish (Asterias vulgaris),

* The second sub-phylum, Pelmatozoa, which includes the Crinotdea, or Feather-stars,.
is represented in deep water as far north as off the coast of Maine by a species
known as Antedon dentatus, but this has not been recorded from Long Island Sound.
Farther south, and: particularly in very deep water, occur other species, including
some of the beautiful “sea lilies.”

 

 

EXpLANATION oF Prate I. Structure of Starfish and Ophiuran.

Fig. 1. Henricia sanguinolenta. Aboral surface of slender-armed speci-
men. (Natural size.)

Fig. 2 Same species. Oral surface of broad-armed specimen. (Natural
size.)

Fig. 3. Same species. Portion of oral surface of disk and one arm, to
show mouth, ambulacral groove, with the two rows of tube-
feet, and spines. (Five times natural size.)

Fig. 4. Asterias forbesi. Small portion of aboral surface, showing the
blunt spines surrounded by circles of pedicellariz, and between
the spines the closely-placed conical or tubular branchiz.
(Much enlarged.)

Fig. 5. Ophiura brevispina, Aboral surface. (Natural size.)

(Figs. 1, 2, and § from photographs loaned by the U. S. Fish Commission

with permission of Dr. H. L. Clark.)
14 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [ Bull.

the slender-armed starfish (Asterias tenera) and the blood
starfish (Henricia sanguinolenta).

Class 2. Ophiuroidea: Ophiurans, Serpent Stars, or Brittle
Stars.— In these forms the body consists of a flattened, circular
central disk, from the under side of which the usually slender,
round arms, with a large number of movable joints, extend
radially. These arms are sharply marked off from the disk
(Plate I), and are provided with strong muscles, which enable
them to be moved in nearly all directions and to be bent in sinuous
or serpentine lines. By the movements of these arms the body
is carried rapidly from place to place, and the flexibility of the
arms enable the animal to hide away in a very narrow crevice.
The mouth is situated as in the starfish, but there is no intestinal
opening.

The ophiurans are represented in Long Island Sound by five
species, only two of which occur abundantly. They comprise the
following: the green serpent star (Ophiura brevispina), the daisy
serpent star (Ophiopholis aculeata), the small gray serpent star
(Amphipholis squamata), and the less common species, known
as Amphioplus abditus, and Amphioplus macilentus.

Class 3. Echinoidea: Echinoids, or Sea-urchins.— Body
nearly circular in outline, hemispherical, or flattened and discoid;
without projecting arms. The calcareous plates in.the skin form
a compact encasement for the body except in the mouth region.
The case is called the shell or, more properly, the test. The
mouth is usually in the middle of the oral surface. The ambulacral
areas, with numerous sucker-feet, in the more typical forms,
extend around the body as meridians from the mouth nearly to
the opposite pole. The spines are movably articulated with the
plates on which they rest.

In Long Island Sound there are four species of echinoids,
which differ so widely in general appearance as to be easily dis-
tinguished. The common purple sea-urchin (Arbacia punctulata)
has a hemispherical test, with long, dark, reddish or purple spines.
The green sea-urchin (Strongylocentrotus drébachiensis) has
shorter spines of a greenish color. The common sand-dollar
(Echinarachnius parma) is very flat and covered with minute
brownish spines. The key-hole urchin (Mellita bentapora) is
No. 19.] ECHINODERMS OF CONNECTICUT. 15

likewise discoid, and covered with minute brownish spines; but
is easily recognized by having five large openings, called lunules,
which pass quite through the body from one surface to the other.

Class 4. Holothuroidea: Holothurians, or Sea-cucumbers.—
The members of this group differ widely in general appearance
from those of the other classes. Our native species all live be-
neath stones or burrow in the sand or mud. Their bodies are
cylindrical and elongated, presenting a closer superficial resem-
blance to worms than to any of the other groups of Echinoderms.
This worm-like appearance is greatly enhanced by the absence
of any closely connected skeletal structures, and by the soft, bag-
like, highly muscular skin. The skin has, however, isolated cal-
careous plates, often of such peculiar and definite shapes that the
species are easily recognized by even a single plate. The mouth
is situated at one end of the body, and is surrounded by a circle
of branched tentacles. The anus is at the opposite end of the
body. The animals move both by means of sucker-feet and by
worm-like contractions of the body.

In Long Island Sound there are probably six species belong-
ing to this class, although only four of these have as yet been
recorded from Connecticut waters. The common Thyone
(Thyone briareus) lies buried in soft mud in shallow water in
great numbers in certain localities. Sometimes the animals have
only the posterior end of the body projecting above the surface
of the mud, but at other times they show also the anterior end
with its circle of branched tentacles of black or purple color.
The two other species of Thyone, T. unisemita and T. scabra are
rare, and occur only in rather deep water.

Our fauna includes also two species with very slender bodies
belonging to the genus Synapta. These are peculiar in having
calcareous plates in the form of perfectly shaped anchors im-
bedded with other plates in the skin. Synapta inherens is white
in color, while Synapta roseola is pink or reddish. Both live in
sandy localities between tides.

Finally, there is the beautiful sea-cucumber (Cucumaria
pulcherrima), which is rarely seen alive, but specimens of which
are sometimes thrown up on the beach by the waves following
16 | CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.
a storm. Little is known of its habits, but it is thought to live
buried in the sand below low-water mark. It is short and thick,
with firm body walls of a whitish color, and has peculiar plates
in the skin.

The species enumerated above comprise all the Echinoderms
known to occur in Long Island Sound, although the biological
survey of these waters is far from complete. It is quite probable
that future investigations will reveal the presence of additional
species. The fauna of the eastern portion of the Sound ineludes
more species than that of the western portion, because of its more
varied physical conditions and its immediate connection with the
Atlantie sea bottom.

Although the Echinoderms of this region are of no value
commercially, they are of great economic importance because of
the enormous injury which results from the depredations of the
common starfish on the oyster beds. The members of the other
classes feed mainly on seaweeds, minute organisms, and organic
matter found upon the rocks and in the mud and sand between
tides and covering the floor of the sea. They are therefore quite
harmless to human interests, and are of some economic value in
that they furnish a portion of the food supply of some of our
edible fishes. Although covered with so firm an armor of de-
fensive plates and spines, such species as the sand-dollar
(Echinarachnius parma), the key-hole urchin (Mellita penta-
pora), and the species of serpent stars are nevertheless greedily
devoured by the cod and other fishes. The holothurians with
their less formidable plates are seized by various species of fishes,
dragged from their burrows, and devoured. In their larval
stages, too, the Echinoderms of all classes are eaten in enormous
numbers by the surface fishes. It is however difficult to estimate
the actual importance of these animals in respect to the human
food supply.

_ The various groups of Echinoderms are likewise of great
scientific interest, because of their remarkable anatomical struc-
ture, their peculiar modes of development, and their curious
habits. No other group of the animal kingdom illustrates more
clearly the modifications which the same organ-system can undergo
in its adaptations to a great variety of functions. The se
No. 19.] ECHINODERMS OF CONNECTICUT. 17

as to the relationships of the present-day Echinoderms, supported
by an abundance. of paleontological material, furnishes one of
the best proofs of evolution.

Specimens of all classes of Echinoderms may be preserved in
80 per-cent alcohol. Formalin should not be used unless abso-
lutely necessary, and should then be replaced by alcohol as soon
as possible. Starfishes, serpent stars, and sea-urchins may be
narcotized by adding magnesium sulphate (Epsom salts) to the
sea water in which they are placed, and then killed by short
immersion in fresh water or weak alcohol. They should then -
be placed in 50 to 70 per-cent alcohol for a few hours, and
afterward preserved in 80 per-cent alcohol. For the preserva-
tion of holothurians with their tentacles expanded, it may be nec-
essary to add the magnesium sulphate to the sea water very
gradually. Otherwise the animals may contract vigorously.

Starfishes, ophiuroids, and echinoids make useful specimens
when carefully dried. But all such specimens should be killed
as indicated and placed for a day or two in strong alcohol. They
should then be dried thoroughly by artificial heat. To prevent
future injury from insect pests it is desirable to add a very minute
quantity of corrosive sublimate to the alcohol in which the spec-
imens to be dried are first preserved. It must be remembered
that corrosive sublimate is a most powerful poison and must be
handled with very great care.

The general scope of this report does not admit of an ex-
tended account of the internal structure of the various species
included. For those who desire to make a thorough study of
the organs of the body cavity of these animals the detailed de-
scriptions given in various handbooks and laboratory guides in
zoology are available. In the following chapters, therefore, will
be given only such descriptions of the external features and
internal organs as are necessary for an understanding of the
relationship of the various groups, their natural history, includ-
ing habits and life history of the various species, and for the
accurate determination of each species.

Under the description of the species, only those characters
which serve to distinguish our native species or have a direct
bearing on their mode of life will be mentioned. More detailed
anatomical descriptions of most of the species may be found in

2
18 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. {Bull.

a report by Hubert Lyman Clark, entitled, “The Echinoderms
of the Woods Hole Region;” published in 1904, in the Bulletin
of the United States Fish Commission for 1902. Many of the
species are described, with interesting observations on their
natural history, in Verrill and Smith’s report on the “ Inverte-
brate Animals of Vineyard Sound and Adjacent Waters,” pub-
lished in 1874, in the Report of the Commissioner of Fish and
Fisheries. Other papers, which deal with particular species or
groups of species, are mentioned under the separate species, while
some of the more general treatises on the Echinoderms are in-
cluded in the Bibliography at the end of this report.
 

 

 

 

 

PLATE II. Skeleton of Starfish, Asterzas forbesz, ( Natural size )
No. 19.] ECHINODERMS OF CONNECTICUT. 19

CLASS I. ASTEROIDEA

The members of this group, popularly known as starfishes,
are represented in Long Island Sound by three, or perhaps four,
species, one of which is the commonest echinoderm found along
the coast. They occur at all depths below low-water mark,
and prefer rocky and shelly bottoms as a rule, because the
mollusks which constitute a large part of their food are most
abundant in such situations. They sometimes live on sandy,
muddy, and gravelly bottoms, and are sometimes found adhering
to piles of wharves. They are often found between tides, hiding
beneath seaweeds or rocks in the tide pools, where they wait
until the return of high water to resume their search for bar-
nacles or mollusks adhering to the rocks.

All the species of starfish found in this region have normally
five broad rays attached to a central disk (Plate II), although
individual specimens having either more or less than this number
are by no means rare. This variation in the number-of rays is
of much interest and is discussed in some detail on page 43.
Along the northern coasts of New England lives a species which
regularly has six rays and another which has ten; and in other
parts of the world are species in which the number of rays in-
creases with the growth of the animal until there may be as
many as twenty to forty, or even more.

The starfishes creep slowly along by means of numerous tube-
feet arranged in longitudinal rows on the under side of the rays.
They can twist the flexible body and arms into almost every
conceivable shape; and, if turned over, they can easily right
themselves.

 

 

EXPLANATION OF PLate II. Skeleton of Starfish, Asterias forbesi.
(Natural size.)

Photograph of dried skeleton from aboral surface, showing the reticu-
lated skeletal plates bearing conspicuous spines. The skin has been mostly
removed. The madreporic plate appears as a circular white spot between
the bases of the two lower arms, while the circle of six small spines just
to the left of the center of the disk indicates the position of the intestinal
opening.
20 CONNECTICUT GEOL, AND NAT. HIST. SURVEY. [ Bull.

Their rapidity of growth is largely dependent upon the
abundance of their food supply. Very young starfishes may
_ double their size within a few days when food is abundant. The
older ones grow comparatively more slowly, but far more rapidly
than was formerly supposed. The rate of growth of our common
starfish is discussed on page 40.

The previous food supply has a great effect on the size of
the animal when sexual maturity is reached, some individuals
being several times the size of others at the first breeding season.
After the discharge of the sexual products growth is resumed,
and may continue year after year, the oldest animals being as
a rule the largest.

When no food is to be obtained, however, the starfish can live
for months without apparent loss of vitality, the size being some-
what decreased in the meantime.

EXTERNAL STRUCTURE

The class Asteroidea, which comprises the starfishes, is dis-
tinguished from the other classes of Echinoderms by the presence
of a central disk which merges gradually, without sharp de-
marcation, into the broad, radially arranged arms, or rays. The
rays themselves are hollow, and contain portions of the digestive
and reproductive systems and other organs.

The upper surface of disk and rays is termed the aboral, or
abactinal surface, while the lower surface, having the mouth in
the center of the disk, is the oral, or actinal, surface.

Between the bases of two of the rays on the aboral surface is
situated a peculiar skeletal plate, the madreporic plate, or madre-
porite. In spite of its small size this plate is often conspicuous
from the fact that it is of a different color from that of the adja-
cent surface of the body. If examined with a lens it may be seen
to be pierced by numerous irregular openings, by means of which
the sea water from the exterior may enter the water-vascular
system (Plates II and III).

This madreporic plate may indicate the plane of symmetry in
the body of the starfish, for a line passing through this plate
and the axis of the ray opposite will divide the body into two
nearly symmetrical portions, sometimes spoken of as right and
 

 

 

 

 

PLATE III. Aboral surface of Starfish, Asferéas forbesz, Photograph of living
animal. (Natural size.)

 
No. 19.] ECHINODERMS OF CONNECTICUT. 21

left. The two symmetrically placed rays adjacent to the madre-
poric plate constitute the bivium, while the three remaining rays
form the trivium.

Body Walls. — The body walls, of both disk and arms, are
supported by a network of articulating calcareous plates, or os-
sicles (Plates II and VIII), held together by connective tissue and
muscular fibers. Imbedded. in the body walls everywhere over
the surface of the body are blunt calcareous spines, arranged
in a more or less definite order, varying somewhat in different
species, and often movable upon the underlying plates.

Covering the whole surface of the body, including even the
spines and pedicellaria, is a delicate membrane or skin, clothed
externally with closely placed vibratile cilia (Plate III). The
rapid vibration of these cilia keeps the sea water surrounding the
body in constant motion.

Branchiz. — In the smooth area between the spines the body
wall is furnished with a multitude of protrusible filaments, the
branchiz (Plate I, fig. 4; Plate III), or respiratory processes,
which have very thin walls and are filled with the fluid of the
body cavity. When fully extended, an exchange of gases may
occur between the contained ccelomic fluid and the external sea
water, thus serving the purpose of respiration.

Pedicellarize. — Scattered over the surface of the body in
many species of starfishes, and arranged in groups at the bases
of the spines (Plate III), occur great numbers of minute forceps-
like or scissors-like appendages, called pedicellaria. Each of
these organs is provided with stropg muscles which enable it
to close tightly under the proper stimulus and thereby seize
any tiny object with which it may come in contact. In the smaller
pedicellarize the two blades cross like a pair of scissors, while
the others are like straight forceps (Fig. 8). By passing the
objects from one to another, the pedicellariz can by their united

 

 

EXPLANATION OF Puate III. Aboral surface of starfish, Asterias forbesi.

Photograph of living animal. (Natural size.) Each of thie large,
blunt ‘spines is surrounded by a circle of tiny whitish pedicellariz, while
other pedicellariz and numerous minute tubular branchie are scattered
irregularly over the dark colored skin between the spines. The madre-
poric plate is seen as a dark, circular area between the bases of the two
lower arms.
22 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. {Bull.

efforts remove any small foreign body from the surface of the
disk or arm and thus serve to keep the body clean. They also
serve to protect the delicate skin from attacks of such small
enemies as might otherwise cause serious injuries.

In the blood starfish (Henricia) pedicellarie are absent, the
body in this instance being protected by the multitude of closely
set spines (Plate I, figs. 1— 3; Plate XI), which cover all
parts of the aboral surface.

Mouth.— Turning now to the oral surface of the body, the
mouth may be seen to occupy the central portion of the disk.
Surrounding the mouth are five groups of movable spines (oral
spines, or mouth papille), forming the five angles of the mouth
(Plate VIII). By means of muscular contractions the oral
spines may be brought together to close the mouth opening, or
may be opened widely to allow the extrusion of the stomach, as
indicated in the two photographs on Plate VIII.

Tube-feet.— Extending outward from the mouth are five
deep grooves, the ambulacral grooves, one of which occupies
the oral surface of each arm (Plate IV). In these grooves are
situated the locomotor organs of the starfish, consisting of a
multitude of finger-like sucking tubes—the tube-feet —ar-
ranged in definite rows throughout the length of the arm. In
the species of Asterias (Plates IV and 1X) there are four such
rows of tube-feet, while in Henricia (Plates I and XI) there are
but two. The rows are placed symmetrically on each side of
the axial line, as shown in Fig. 2.

Each tube-foot consists of a muscular tube with a circular
disk at the free end (Fig. 1). The tube leads between the os-
sicles forming the roof of the ambulacral groove, and connects
internally with a sac-like swelling —the ampulla, — and _ also,
by a narrow tube, with the radial canal of the water-vascular
system. ‘The relations of these parts are shown in Fig. 1.

 

 

Pirate IV. Oral surface of starfish, Asterias forbesi. (Natural size.)

The ambulacral grooves are widely opened, disclosing the four rows
of crowded tube-feet, each with its terminal sucking disk. In the center
of the disk appears the delicate, baglike stomach, partially everted, as in
the beginning of the act of feeding. The photograph shows two rows
of slender adambulacral spines along the borders of the ambulacral grooves,

and the large blunt spines, surrounded by minute pedicellariz, nearer the
sides of the arms.
 

 

 

 

 

( Natural size.)

PLATE [V, Oral surface of Starfish, Asferzas /orbesz.
No. .19.] ECHINODERMS OF CONNECTICUT. 23

Both ampulle and tube-feet have highly muscular walls, and
both are filled with fluid from the water-vascular system. When,
in locomotion, the ampulla of any particular tube-foot is con-
tracted, the fluid contained therein is forced into the tube-foot
itself, extending this organ until it becomes a long, finger-like
process. On coming in contact with any external object the
disk at the end of the tube-foot may be pressed tightly against
it. If now the muscles of the tube-foot contract, the water which

 

t

Fic. 1. Transverse section of a decalcified ray of a young starfish,
showing the relations of the internal organs. The two ampulle (amp)
open by wide canals into the tube-feet (#), the water supply of which is
provided by the radial canal (rc). The openings into the ampulle from
the radial canal are furnished with delicate valves, as indicated, which pre-
vent the back flow of the water when the ampulle are contracted and the
tube-feet extended. Beneath the radial canal are the two radial perihemal
vessels (rv), separated by a vertical septum, and beneath these is the
radial nerve-cord (”), which extends from the circum-oral nerve to the
tip of the ray. Sections of the spines (s), branchie (b), and pedicellarie
(p) are indicated. The pyloric ceca (h) are attached by mesenteries to
the dorsal wall of the ray. The spaces between the organs constitute the
celom (c), and are in life filled with a fluid somewhat resembling the
blood, and like it containing floating corpuscles.
24 CONNECTICUT GEOL. AND NAT. HIST, SURVEY. [Bull.

it contains is returned to the ampulla, and at the same time the
foot tends to shorten. As the terminal disk adheres to the ex-
ternal object by the pressure of the water, the shortening of the
foot will tend to draw the body of the starfish towards the point
of adhesion. If many such tube-feet work together, an actual
movement of the body occurs. By the codrdination of the
nervous system of the animal all the tube-feet of any arm or
of all the arms may be extended in the same direction, either to
the right or left, backwards or forwards, as the case may be.
The result is a slow, steady movement of the body.

Suitable muscular contractions of the other body muscles,
combined with the working of the multitude of tube-feet, en-
able the animal to bring about a great variety of movements, by
which it seeks its food, migrates from shallow to deep water or
the reverse, rights itself when accidentally thrown upon its aboral
surface, and forces apart the valves of the shells of the mollusks
on which it feeds, as described on page 30. By such means,
moreover, the starfish can so change the shape of its body as to
occupy small crevices in the rocks, creep through small open-
ings, and adapt itself to any surface with which it may come
in contact.

Ossicles. — The roof of the ambulacral groove is formed by
a series of interlocking movable plates, the ambulacral ossicles,
arranged in a double row articulating with one another at the
apex of the groove in such a way as to open or close the groove
when required (Plate VIII).

On each border of the ambulacral grooves is a regularly
arranged row of plates, adambulacral ossicles, which bear the
adambulacral spines (Plate VIII). These~ spines may all be
turned toward the middle line of the groove in such a way as to
form a protection for the tube-feet.

The two rows of ambulacral ossicles end in a single terminal
ossicle at the tip of the arm. This ossicle supports a terminal
tentacle, endowed with a sensory function, presumably both
tactile and olfactory in nature. At the base of the tentacle the
radial nerve ends in a minute, orange-colored, eye-spot.

Between the ambulacral ossicles are the pores by which each
of the tube-feet is connected with the corresponding ampulla,
situated internal to the ossicle. The firmly interlocking ossicles
 

 

 

PLATE V. Anatomy of Starfish, Asterias vulgarés, (‘Two-thirds natural size.)
No. 19.] ECHINODERMS OF CONNECTICUT. 25

which form the skeleton of aboral and lateral surfaces of the
disk and arms are shown in Plate II.

INTERNAL STRUCTURE

If the body of a starfish be opened by removing with fine
scissors the body walls of the aboral surface of the disk and one or
more arms, as indicated in Plate V, the internal organs are easily
exposed. The most conspicuous viscera are the various portions
of the digestive system, and, in certain seasons of the year, the
reproductive organs.

In the dissection shown on Plate V, the five cardiac pouches
of the stomach (¢. ¢) lie beneath the five-lobed pylorus (p. c),
into which open the profusely branched digestive glands, pyloric,
or hepatic, caeca (h. c). The madreporic plate (m. p), rectal
ceca (r. c), ambulacral braces (a. 0), retractor muscles of
stomach (7. m), vertebral ridge (v. r) and sexual glands (s. g)
are shown. In the lower left-hand ray the pyloric czca are laid
aside and the sexual glands removed to show the ampulle of
the tube-feet on each side of the vertebral ridge. In the median
ray the hepatic caeca are removed completely to show the position
and extent of the sexual glands (s. g).

Alimentary Canal. — The digestive system of the starfish is
modified to conform with the general-shape of the body. The
small, centrally placed mouth leads by a short esophagus into
the spacious cardiac portion of the stomach. The latter is pro-
vided with five broad lobes, cardiac pouches, opposite the bases
of the five arms (Plate V). The walls are very thin, much
folded, and muscular, so that this portion of the stomach can
be completely everted from the mouth opening and wrapped
around such food as the animal secures. After the prey has been

 

 

EXPLANATION OF PLate V. Anatomy of starfish, Asterias vulgaris. (Two-
thirds natural size.)

Dissection from aboral surface to show internal anatomy; a.0, am-
bulacral braces; c. c, cardiac portion of stomach; h. c, hepatic ceca; m. p,
madreporic plate; p.c, pylorus; 7.c, rectal ceca; r.m, retractor muscle;
s.g, sexual glands; v.r, vertebral ridge. : ae

The lower right ray shows the viscera in their natural position. In
the lower left ray the sexual glands and retractor muscles have been
removed and the hepatic caca separated to show the ambulacral ossicles
and ampulle of tube-feet. In the upper ray the hepatic caca have been
removed.
26 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.

completely digested, the stomach is again drawn back into the
body cavity by means of five pairs of long retractor muscles,
which are attached to the upper side of the ambulacral ossicles
in the rays, as shown in Plate V.

At its aboral end the cardiac stomach is constricted and
leads into a narrower cavity, the pylorus, from which five pairs
of large, profusely branched pyloric, or hepatic, caca (Plate V)
extend outward into the cavities of the rays. These ceca form
the digestive fluids, which are able to act on fats, proteids, and
carbohydrates. From the pylorus a short and narrow intestine
(Plate V) leads to a minute anal opening on the aboral sur-
face near the center of the disk, and on a line between the bases
of the left and middle rays of the trivium. Connected with
the intestine are two small glands, the rectal ceca (Plate V),
which doubtless excrete waste products, to be discharged from
the body through the anus.

As stated on page 32, whenever any considerable amount
of refuse remains after digestion such substances are thrown out
of the mouth. Consequently the intestine has little use except
as an excretory organ.

Water-vascular System.— The complex system of vessels
constituting the water-vascular, or ambulacral, system are of
great importance in the locomotion of the body, as described
above under the heading, “ Tube-feet.”

The madreporic plate serves as a sieve (m, Fig. 2) through
which the external sea water enters the water-vascular system.
This plate connects with the madreporic canal (the so-called
stone canal), which leads into a large circular vessel surround-
ing the mouth. From this vessel a large radial vessel runs along
the roof of the ambulacral groove to the tip of each arm. The
radial vessel gives off paired lateral branches to the tube-feet
(Fig. 2). The latter are all arranged in two rows on each side,
and those of the two rows alternate. Consequently longer and
shorter lateral branches alternate. The action of these tube-feet
in locomotion is explained on page 23. Connected with the in-
ternal border of the circular vessel is a series of nine glandular sacs
known as Tiedemann’s bodies, shown in the diagram ( Fig. 2).
These sacs give rise to amcebocytes, or cells which float about
in the fluid of the water-vascular system. They probably serve
No. 19.] ECHINODERMS OF CONNECTICUT. 27

an important function in the collection and discharge of the waste
products of the body.

 

Fic. 2. Diagram of water-vascular system of starfish; m, madre-
poric plate; s. c, stone canal; T, Tiedemann’s body; o. ¢t, oral
tentacle; ¢. f, tube-foot; amp, ampulla; r. c, radical canal; c. c,
connecting canal; 7, ring canal.

Circulatory System. — A complex system of vessels running
parallel with the vessels of the water-vascular system is termed
the perihzemal system. The principal vessels of this system are
divided into two parallel chambers by a vertical septum. In
the septum is a smaller central canal which contains a small
amount of fluid, and is ‘thought to constitute the true blood
system. This latter has therefore radial and circular canals,
parallel both to the water-vascular and to the perihzemal system.
The radial vessels are shown in section in Fig, 1.

Nervous System. — The nervous system consists of a nerve
ring surrounding the mouth, with a large radial nerve extending
outward along the roof of the ambulacral groove of each arm
and terminating in an orange-colored eye-spot at the tip of the
arm. From the radial nerves minute branches are given off
to each tube-foot and ampulla, to the superficial integument,
28 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.

and to the muscles and organs in the body walls. In addition
to these main nerves is a complex network of fibers supplying
the alimentary canal and other internal organs. Everywhere
over the surface of the body is a network of minute fibers con-
nected] with the sense organs, pedicellarie, and branchiz of the
integument.

The whole nervous system controls the codrdinated actions
of all parts of the body only when the connection with the nerve -
ring is intact. If the radial nerve at the base of one or more
of the arms is cut, each arm so isolated from the nerve ring will
act independently of all the others, and no coordinated move-
ments of the body are possible. The nerve ring may therefore
be looked upon as the coédrdinating center of the nervous system
of this animal.

Reproductive System.— The sexes are separate, with paired
sexual glands extending into each arm. These glands develop
in close connection with the madreporic canal in a mass of
tissue known as the axial organ. The development of the sexual
products is described in detail in the chapter on reproduction.

HABITS
Many interesting papers have been published in recent years
describing in great detail the habits of various species of star-
fish and their responses to stimuli. In addition to the classical
works of Romanes* and Preyer,t the papers of Cole,§ Cowles,f
Jennings,** von Uexkill{+ and others discuss the behavior of
these animals when subjected to a great variety of conditions.

*In addition to several more technical papers, the book entitled, “ Jellyfish,
Starfish, and Sea-urchins,” published in the International Scientific Series, 1885,
contains a most interesting popular account of the natural history of the starfish.

+ Ueber die Bewegungen der Seesterne, Mitteilungen aus der Zool. Station zu
Neapel, Band 7, 1887.

§ Cole, L. J., Direction of Locomotion of the Starfish (Asterias forbesti), Pub-
lished in Science, vol. xxxi, 1910. This paper consists of a brief statistical study
of the direction of movement of our common starfish in the absence of directive
stimuli.

1 Cowles, R. P., Reaction to Light and other Points in the Behavior of the Starfish.
In Publication No. 132, Carnegie Institution, Washington, 1909. Describes the
reactions of two species of starfish when subjected to various kinds of light,

** Jennings, H. S., Behavior of the Starfish Asterias forreri de Loriol. In the
University of California Publications in Zodlogy, vol. iv, 1907. Observations on
the habits of a species of Pacific Coast starfish and its reactions to various kinds
of stimuli,

t+} In addition to several technical papers by von Uexkilll, a Popular account of
the general behavior of the starfish is contained in his recent book entitled, “ Umwelt
und Innenwelt der Tiere.”
No. 19.] ECHINODERMS OF CONNECTICUT. 29

The general mode of life of the starfish, including habitat,
locomotion, changes in shape of body, and migration, are briefly
discussed in the following chapters, and the nature of this Report
does not justify further details. The subject of habit formation,
however, as described by Jennings* may be briefly outlined here.

“The behavior of the starfish is in general characterized
by what might be called versatility; the animal can do in many
different ways anything that it can do at all.” In its locomotion,
for example, it may move with equal facility in any direction
along the plane of its body without any regard to right or left,
or forwards or backwards. Under the same conditions its be-
havior is subject to the greatest variations, and it may be said
never to do the same thing twice in exactly the same way.

When subjected to experiment it was found to solve the prob-
lem set for it, such as escaping from cramped quarters, removing
rubber bands from its rays, etc., in a great number of different
ways on successive occasions. But whenever left to itself it
showed no improvement in solving these problems. It never
learned to select the most effective method; that is, it failed to
form the habit of employing this method when confronted again
with the same problem.

But attempts to train the starfish were not altogether un-
successful; for example, when placed on its aboral surface,
the animal may right itself by employing any two adjacent arms,
different pairs being used on successive occasions. Yet by pre-
venting the use of certain arms the animal may be success-
fully trained to use certain other arms on all occasions. But the
effects of this training are soon lost, so that on the following
day the starfish shows no effect of its training. By giving the
animal ten lessons a day for eighteen days, however, the starfish
may show the effect for at least a week. By long continued
training it is probable that still more lasting habits might be

induced.
FOOD
One of the species of asteroids occurring in Connecticut
waters, the common starfish (Asterias forbesi), causes a vast
pecuniary loss each year because of the enormous numbers of

* Johns Hopkins Univ. Circulars, No. 3, 1907; also Univ. Calif. Publications in
Zodlogy, vol. 4, 1907.
30 CONNECTICUT GEOL. AND NAT. HIST, SURVEY. [Bull.

oysters which it devours. The extent of this loss is difficult
to estimate, and the reader is referred to page 33 for an account
of the injuries thus caused.

The most usual food for all the species consists of mollusks
and crustaceans, of which the various species of mussels, the
oyster, the two common species of clams, and barnacles, furnish
the principal supply. Univalves, or sea snails, of various species,
and other invertebrates, are devoured whenever they can be
secured; and indeed almost any small animal when injured or
dead may be eaten. The larger starfishes may even devour small
individuals of the same or of different species. The common
starfish is occasionally of actual benefit in that it devours the
univalve known as the oyster drill (Urosalpinx cinerea), which
is itself a serious enemy of the oyster. But it does this only
when oysters or other bivalves are not obtainable.

The starfish secures its prey by seizing it with the tube-feet
and then drawing it toward the mouth. The mouth, however,
is itself of small size as compared with the body of the star-
fish, being only about one-fourth to three-eighths of an inch in
diameter in a moderately large animal. Only objects of small
size can therefore be taken directly into the stomach. If the
prey be too large to pass the mouth, which is the case with
the greater part of the food, the soft, sac-like stomach is everted
from the mouth and wrapped around the prey, after which
digestive fluids are poured out and digestion ensues. After the
absorption of the nutritive substances contained in the body
of the prey, the stomach is again drawn into the body of the
starfish, by means of a special set of retractor muscles.

If a large bivalve be secured, as a large oyster, clam, or
mussel, the shell must be opened before the food can be devoured.
But it is obvious that the strength exerted by the tube-feet of
the starfish will have little immediate effect on the powerful
muscles which hold together, and close tightly, the two valves
of a large oyster or quahog. Many theories have been proposed
in the attempt to explain the process by which these mollusks
are opened by the starfish. It was formerly thought that the
starfish excreted a poison which found its way between the
valves of the shell and finally stupefied the mollusk sufficiently
for the valves to gape and allow the starfish to insert its stomach.
No. 19.] - ECHINODERMS OF CONNECTICUT. 31

But experiments show that a mollusk taken away from a star-
fish which had opened it, soon regains its normal condition.
Another theory was that the starfish wrapped its stomach about
the mollusk’s shell, depriving the animal of oxygen and effec-
tually smothering it. But observation shows that such is not
the case. Another theory that has been held is that an acid
dissolves the edges of the shell, but no such acid is present.
Others have believed that the edges of the shell are chipped
sufficiently to allow the entrance of the starfish’s stomach; and
it is true that the delicate edges are often accidentally broken by
the starfish, but such a shell can still be closed so tightly as to
hold water.

Thus the problem remained unsolved until 1896, when the
experiments of Schiemenz* showed that simply the long con-
tinued pull of the starfish’s arms will eventually overcome the
resistance of the adductor muscle which holds the two valves
of the shell together. While the muscle can resist for a short
time a very strong pull tending to separate the valves, the muscle
eventually becomes fatigued, and relaxation allows the valves
to gape. In the same way, if a sufficiently stout cord is tied
around the foot of a large marine snail, a strong man is unable
to pull it from the shell. Yet such a snail is unable to support
its own weight, by the same muscles, for a long period. After
being suspended for a time by the foot, the muscles become
fatigued and relax, allowing the body and shell to hang loosely
at the end of the fully extended foot.

Schiemenz demonstrated that the starfish was able to exert
a pull of more than 1,300 grams, while it required a force of
only goo grams to fatigue the muscles of a large bivalve so
that the shell would gape widely within a half-hour.

It is only necessary therefore for the starfish to grasp the
oyster with the tube-feet of opposite arms attached to the valves,
and then continue pulling in opposite directions until the mol-
lusk’s adductor muscle becomes sufficiently fatigued to allow the
valve to open. But a considerable force is required in order
to accomplish this, and it is only when the arms of the star-
fish are wrapped around the shell of the bivalve in such a
manner that the tube-feet in the basal portions of the arms can

eda foe
* Mitteilungen des deutschen Seefischervereins, 1896.
32 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. ({Bull.

pull at right angles to the valves that the shell can be opened.
Thus a starfish finds it quite impossible to open a bivalve when
held with its arms outstretched beween two glass plates, even
when there is plenty of room for it to carry the bivalve about
with it.

After the resistance of the adductor muscle of the mollusk
is completely overcome, the stomach of the starfish is turned out
between the two valves of the shell, and the soft body of the
mollusk is then digested as in the case of a smaller object, leaving
nothing behind except the cleaned and empty shell. Sometimes
two or more starfish participate in devouring a single large
oyster.

The processes concerned in the digestion of a large mollusk
are so complete in the starfish that little if any refuse remains.
But in the case of animals sufficiently small to be taken directly
into the stomach, through the mouth, the indigestible food re-
mains are thrown out of the mouth again. For this reason the
opening of the intestine on the aboral surface of the body is very
small, and serves merely for the discharge of fluid waste ma-
terials secreted by the glands connected with it.

When food is abundant the starfish often devours an
enormous quantity, and growth is correspondingly rapid. The
observations of Mead, on the voraciousness of young starfish,
as noted on page 57, show that as many as 56 clams, some
of which were as long as an arm of the starfish, could be
devoured by a single starfish within a period of six days.

On the other hand, in case food cannot be secured, the star-
fish is able to survive a fast of several months without apparent
discomfort. In the latter case, however, no growth whatever
occurs until food is again secured.

NATURAL ENEMIES

It would seem that an animal so well protected by its spiny
skin and abundant pedicellariz, would be largely exempt from
the attacks of other carnivorous animals of the sea. And in the
adult condition such is actually the case. Occasionally one star-
fish when pressed with hunger will devour another of the same
species; fishes of various kinds destroy mutilated individuals
and probably large numbers of young. Various species of birds,
No. 19.] ECHINODERMS OF CONNECTICUT. 33

as crows and gulls, which frequent the shore, sometimes feed
upon the starfish when other food is difficult to obtain. The star-
fish is said also to suffer occasionally from the effects of a para-
sitic disease.

But the greatest destruction occurs in the very early stages
in the life of the starfish, at the time when the bipinnariz or
brachiolariz, as the embryos are termed, are swimming free at
the surface of the water. At this time such fishes as the men-
haden swim through the water with their mouths widely open
and devour countless numbers of small organisms of all sorts
from near the surface. Among these may be the young of
two species of Asterias, and vast numbers are destroyed in this
way. The young of Henricia develop directly from the egg, and
thus escape the dangers of the free-swimming stage.

How does it happen, then, if there be so few natural enemies
of the starfish after it has assumed the adult condition, that
the sea is not overrun with the creatures to the exclusion of all
other animals? Of the thousands of eggs laid by a female
starfish each year not more than one on the average produces a
sexually mature animal. All the others die; some are destroyed
by the enemies indicated, many die from their inability to obtain
food, others are buried beneath the mud of the bottom, some
are crushed by the rolling pebbles on the shore, still others
succumb to changes in the temperature of the water, many die
from the effects of rain or streams of fresh water, while vast
numbers are left by the tides to be destroyed by drying in the air.

As a result of these many hazards only a small fraction of
one per cent. of the embryos.survive to produce young starfishes
a half-inch in diameter. The few that reach this stage of de-
velopment are comparatively safe.

é

DAMAGE TO OYSTERS AND OTHER MOLLUSKS

There is little realization except among the oyster planters
themselves of the enormous extent to which the starfish is
destructive to the oysters and clams which form such an im-
portant natural resource of the state. The oyster industry alone
produces an annual income of over a million dollars, and
furnishes employment to hundreds of citizens.

3
34 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.

For the year ending June 30, 1910, the receipts in this state
from the sale of market and seed oysters and shells was
$1,892,759, while there remained on the beds in private areas
alone an estimated quantity of 3,784,175 bushels of oysters,
valued, with the stakes and buoys which mark the grounds, at
$1,856,285. During this year the industry gave employment to
2,703 persons.*

For the mere privilege of controlling certain parts of the
floor of the Sound for the cultivation of oysters, the oyster
planters have paid over $260,000 into the treasuries of the state
and the towns adjoining the coast.t+

So serious is the starfish injury to the oyster industry that
the General Assembly of this State, in 1901, passed a law making
it illegal for any person to assist in the spread of the pest. The
law reads as follows: ‘Every person who shall wilfully deposit
or assist in depositing any starfish . . . . in any of the
navigable waters of this State . . . . shall be fined not more
than fifty dollars, or imprisoned not more than six months.”
(Connecticut Shell-fish Commissioners’ Report for 1903, page
XXvi.)

The actual loss which the starfish causes to the oyster in-
dustry of the state is very difficult to determine with any de-
gree of precision. Any estimate even of the losses to a single
grower is, from the very nature of the case, largely a matter of
guess-work. Furthermore the natural beds suffer a great annual
loss, of which no one takes account. The loss to the new set,
when the individual is but a small fraction of an inch in diameter,
may actually be, and probably often is, greater than that caused
by the more conspicuous destruction of oysters of larger size.
The oyster grower who watches his plantations carefully knows
when the starfishes of larger size become numerous on_his beds,
but he has no means of determining the injuries caused by the
young individuals to correspondingly young oysters. The fact
that a single starfish less than a month old has been shown to
be able to devour more than 50 young clams in six days, indicates
how extensive these injuries may become.

 

* Report to the General Assembly, State of Connecticut, on the Investigation of
Oyster Properties by the Board of Equalization, 1910, page 77.
+ Report Shell-fish Commissioners, 1907-08, page 82,
No. 19.] ECHINODERMS OF CONNECTICUT. 35

On the privately controlled beds regular examinations are
made for the presence of the starfishes, and, whenever they are
found in unusual abundance, it is imperative that immediate
steps. be taken to destroy them. This is accomplished by the use
of mops, as described below, by means of which the larger star-
fishes are caught and killed.

By such thorough and regular inspection the very extensive
injuries of former years have been largely controlled, and the
oyster grower of to-day, like the fruit grower on the land, always
reckons upon a certain expense for the destruction of pests.

The actual expense of this method of controlling the star-
fish varies somewhat from year to year; and, while an accurate
estimate of the total amount is not available, it is known to be
very great. And yet, as in the case of the fruit grower, it is
but a fraction of the amount that would inevitably be lost if
such measures were not taken.

During the year 1909, inquiry as to the number of starfish
actually destroyed in carrying out this policy of protection shows
that many thousand bushels of the pests are annually destroyed.
When we consider the fact that each bushel will contain several
hundred starfish, the number, of course, varying with the size,
we may gain some conception of the vast number destroyed.

In reply to an inquiry, the following statements by a promi-
nent oyster planter may be considered as expressing the most
accurate information obtainable. “The starfish seem to vary
in different localities from month to month, but the average on
the whole seems to keep up remarkably high, considering the fact
that such a vast quantity of these destructive creatures are caught
by the oyster steamers.” “ We have not at command definite
amounts that are caught per year, but in ‘a general way would
say that they probably run from 5,000 to 10,000 bushels per
year. Some years they may exceed the latter figure.”

The excessive abundance in restricted localities often oc-
casions great alarm among the growers, but of late years success
* has invariably rewarded the determined effort to combat the pest
upon any particular bed. Sometimes, however, it must be ad-
mitted that this result has been attended with very great expense.

Although it is probable that the injuries during recent years
are on the whole less than in some former years, yet the total
Missing Page
Missing Page
38 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. (Bull.

'“ There is, consequently, a community of interest among
the planters, in attacking and destroying the star. For, in pro-
tecting his own beds, a man also assists his neighbor to whose
tracts the stars might go, and, conversely, any neglect of one’s
own ground constitutes a menace to all cultivators in the vicinity.

“ The work of destroying stars is a duty, as before intimated,
in which the natural-growth oysterman usually takes no part.
He takes the oyster where he can find it, appropriating the bounty
of heaven without accepting any responsibility as to the conserva-
tion of a further supply.”

Whenever the starfishes are found upon an oyster bed in
excessive numbers, the oyster grower sends out his boats with
the star-mops, or tangles, which are dragged back and forth
systematically over the bed. ‘

“When the star-mop is drawn to the surface, its load of
stars is deposited in a vat or tank and treated with boiling water
or live steam. The oyster boats are well equipped with ap-
paratus for this purpose, the steam or water being conveniently
taken from the vessel’s boiler, though some of the steamers have
special boilers for this purpose.

“Attempts have been made to turn to some useful purpose
the large quantities of stars taken from the oyster beds of Long
Island Sound, and it goes without saying that this should be a
more or less valuable by-product of the industry. Properly
mixed with other material, they constitute a valuable fertilizer.
Frequently, farmers residing in the neighborhood of oyster
planters have contracted for the catch of stars, but the oyster-
men say that in practice it does not work well, as they find that
they cannot depend upon having the accumulation of dead stars
regularly removed from their premises, and of course they can-
not allow them to remain and putrefy. As a consequence, the
usual mode of disposition is to throw them overboard after they
have been killed in the live steam or boiling water bath.”

A perusal of the Reports of the State Shell-fish Commis-
sioners reveals many instances of the excessive losses caused by
starfish in former years. In the report for 1883 the statement
occurs that thousands of bushels of oysters were destroyed in
one locality within a single week. A single firm lost $20,000
No. 19.] ECHINODERMS OF CONNECTICUT. 39

worth in one bed, while another firm suffered a loss of $100,000
in “the last two years.”

The report for 1884 states that 11,000 bushels of the pests
were caught off Stratford during a period of six weeks, but
before the work was completed at least 200,000 bushels of oysters
had been destroyed.

In a paper by Collins on the Oyster Fisheries of Connecticut,
an estimate is made that in 1888 the damage to beds in Connecti-
cut waters amounted to some $651,500. During that year 42,000
bushels of starfish were destroyed.

Appreciating the ability of the starfish to migrate from one
spot to another not far removed, one enterprising firm of oyster
growers has sometimes paid a dollar for each bushel of young
starfish collected on the shores adjacent to their plantations.
Such a procedure is doubtless profitable to all the parties con-
cerned; for, when the young starfish are abundant, the dollar
is easily earned, and the destruction of so large a number of
small starfish as may be contained in a bushel basket — occasion-
ally as many as 2,000 very small ones — will undoubtedly reduce
the expense of protecting the beds by more than the sum ex-
pended.

Not only is there great destruction of oysters, but other mol-
lusks of economic importance, as the clams and mussels, suffer,
perhaps, to an even greater proportional extent. The mussel
is one of the chief natural food supplies of the starfish, but, as
this mollusk is little used commercially in Connecticut, the pe-
cuniary loss is not of importance. The injury to the clam, on
the other hand, which furnishes an important article of food, is
a matter of some real concern to the people of the state. The
barnacles, worms, crustacea, and various gastropod mullusks,
from which the starfish derives a portion of its food supply,
have little to do with human welfare; and, whenever the star-
fish supplements its diet by devouring one of its own kind, or
when it feeds upon the mollusk known as the oyster drill, it
becomes, for the time being, of distinct service. Likewise, in
furnishing a portion of the food supply, either directly or in-
directly, of certain fishes used for human food, it compensates
to some slight extent for the damage which it causes.
40 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.

RATE OF GROWTH

The rapidity with which starfishes increase in size, and the age
at which sexual maturity is attained, have long been subjects for
discussion among zodlogists. A number of years ago Alexander
Agassiz estimated the growth and age of the common starfish,
and came to the conclusion that it required about fourteen years
for the animal to reach its full development. It was thought
to begin to spawn before that time, apparently at six or seven
years of age.

Professor Mead, however, has settled this point beyond dis-
pute* by actually rearing large numbers of young starfishes from
the time when the free-swimming larve attach themselves to
the eelgrass and other objects in preparation for their trans-
formation to the adult form.

By keeping these young starfishes in aquaria and submerged
cars and feeding them regularly, a most surprising rapidity
of growth was found to result. On June 29th the stars measured
on the average only about Imm. from mouth to tip of arm;
on July 18th, 5mm.; July 26th, 9mm.; August 18th, 18mm.;
Sept. 26th, 35mm.; and on Oct. 25th, 54mm. Such stages of
growth are represented in their natural size on Plate VI, from
Mead’s report in the Bulletin of the U. S. Fish Commission
for 1899.

Figs. 1 to 3, on Plate VI, show small individuals taken from
seaweed soon after having completed the free-swimming stage.
Fig. 4 shows the average size found on eelgrass and seaweed
about two weeks later, July 15, and Fig. 5 a large individual
of the same age which was reared in a submerged car and well
supplied with food. A similar individual reared in car, three
days later, is shown in Fig. 6; and one after eight days more, July
26, in Fig. 7. Figs. 8, 9, and 10 indicate the size of the young
starfishes about four weeks, six weeks, and nine weeks after
having completed the free-swimming stage. Fig. 11 shows the
growth in three weeks more, while Fig. 12 indicates the size
attained by a large individual reared in submerged car with
an abundance of food, at about 4 months of age.

SS

* Mead, A. D., On the Correlation between Growth and Food Supply ;
American Naturalist, vol. xxxiv, 1900. PPly in Starfish.
i -
ae

 

Growth of Starfish, dsferzas forbest, during the first four months

PLATE VI.
- of life. (Natural size.) After Mead.
No. 19.] ECHINODERMS OF CONNECTICUT. 41

There were larger specimens than those indicated, and also
smaller, for at all times there were some individuals which were
' only a third as large as the others, and all intermediate stages

occurred between the smallest and the largest. Similar series
could be obtained along the seashore at any time during the
summer and fall.

By varying the amount of food supplied, Professor Mead was
able to prove that the rate of growth depended directly upon the
amount of food available. In this respect the starfish behaves
quite differently from the higher vertebrate animals, for the
starfish can assimilate many times as much food as is necessary
for keeping it in good condition, and all the food not required
for the maintenance of the bodily functions is used in the manu-
facture of new tissues, whereby a rapid growth results. Yet a
starfish will live and remain in apparent health for months with
scarcely any food whatever, although no growth takes place
under, such circumstances.

: When the usual food supply becomes scarce, the larger star-
fishes show no hesitation in devouring smaller individuals of
their own kind.

In Fig. 3 are shown outlines of two individuals of the same
age, five and one-half weeks, the small star on .the left repre-
senting a starfish to which but little food was supplied, while
the larger figure shows the size which a well nourished specimen
may reach at the same age.

 

 

EXPLANATION OF PLATE VI. Rate of growth of starfish, Asterias forbesi.

A series of young starfish to show the rate of growth of well-nourished
individuals during the first four months of life. All natural size.
Figs. 1 to 3. Small individuals during the first week after having com-
pleted the free-swimming stage, July 1.
Specimen from eelgrass two weeks later, July 15.

Fig. 4.

Fig. z Specimen reared in submerged car about three weeks after the
completion of the free-swimming stage, July 15.

Fig. 6. Similar specimen three days later, July 18.

Fig. 7. Large specimen from car when one month old, July 26.

Fig. 8. Similar specimen on August 2.

Fig. 9. Similar specimen on August 18.

Fig. 10. Same on September 5.
Fig. 11. Same when three months old, September 26.
Fig. 12. Largest specimen reared in submerged car at the age of four
months, October 25.
(After Mead.)
42 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.

It is of interest to note that the loss of an arm does not cause
even a temporary diminution in the rate of growth, the rest of
the body increasing in size as rapidly as in the case of uninjured
individuals. Even the loss of two arms has little effect. The
lost arms are rapidly replaced if food is abundant, and in their
regeneration grow faster than the others until the normal sym-
metry of the body is restored.

Fic. 3. Outlines of two starfishes of the same age
(5% weeks), showing difference in the rate of growth
Cane — influence of different food supplies. (After

ead.

The age at which the starfish becomes sexually mature is.
also influenced by the rate of growth, for Mead has found that
all starfishes with a length of ray of more than 50 mm. at the
beginning of the breeding season, in May, are sexually mature,
while others, but 10 or 15 mm. long at the same date, do not
deposit sexual products until the following year. Now the
length of 50 mm. is reached by well nourished individuals when
less than four months of age, so that it seems reasonable to con-
clude that the well fed starfishes are ready to breed when a little
less than one year old; that is, in June of their first year.

The rate of growth is most rapid during the warmer months
of the year, and may cease entirely during the winter. This is
probably due in part to the smaller amount of food devoured,
and in part to the development of the sexual products.
Missing Page
No. 19.] ECHINODERMS OF CONNECTICUT. 43

MIGRATION

It is well known that when the food supply in one region is
exhausted the starfishes migrate to other localities, and further-
more there is more or less regularly a seasonal migration from
the tide pools along the shore to the deeper water. But the
extent of such migrations has probably been greatly overesti-
mated, and the sudden appearance of vast hordes in any par-
ticular spot is due more to the very rapid increase in the size of
the small and previously unnoticed starfishes than to the actual
migration of a multitude of individuals. If a starfish should
move constantly in one direction at the rate of six inches per:
minute, which is about its normal rate of progress, it could
travel about a mile per week; but there is no evidence that such
a rate is maintained for more than a few minutes at a time, and
it is probable that the creature is quite as likely to retrace its
steps or to proceed in an irregular path as to continue for more
than a few minutes in any single direction. As stated in the
quotation on page 37, quicklime has proved an efficient barrier,
although the animals can easily pass all kinds of soft or slippery
substances.

VARIATION IN NUMBER AND ARRANGEMENT
OF RAYS

While all of our native species of starfish have normally
five rays of nearly equal size, yet if one examines a large number
of specimens he is likely to notice certain variations. In the
common starfish, for example, careful search may reveal an
individual with but a single well formed ray and other rudi-
mentary ones, while another specimen may have as many as
eight rays, all perfectly formed.

 

 

EXPLANATION oF Pate VII. Variation, Asterias forbesi.

Fig. 1. Four-armed individual, showing no indication of injury.

Fig. 2. Eight-armed individual, provided with two madreporic plates.

Fig. 3. An individual in which one arm is forked or longitudinally

‘ divided nearly to the disk.

Fig. 4. Six-armed specimen.

Fig. 5. One with seven well formed arms.

Fig. 6. An individual in which an injury has removed all the arms of
the disk except one, the four small arms being in process of
regeneration, : .

(All figures two-thirds natural: size.)
44 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. (Bull.

Professor Verrill, of Yale University, has made a large col-
lection of these abnormal specimens, and has recently published*
a paper on the subject. On Plate VII are shown a number of
such specimens. Some of these are the result of injury, others
may have arisen from congenital variation, while others evidently
represent cases in which there has been a partial division of the
body in an early stage of development. Fig. 2, for example,
shows an individual which has eight perfectly formed rays, but
this specimen is also provided with two madreporic plates.
These facts would seem to indicate that in an early stage of de-
velopment, perhaps even at the time of the first cleavage of the
egg, the body became partially divided into two incomplete in-
dividuals. As development proceeded, these twins, as they may
be called, remained attached together, each provided with four
rays and the usual madreporic plate. A further and complete
separation might result either in two normal individuals, identi-
cal twins, or in such specimens as the one shown in Fig. 1. On
the other hand it seems possible that the four-rayed starfish of
Fig. 1 may have resulted from an early injury and loss, without
regeneration, of the missing arm; or as a so-called congenital vari-
ation, that is, one which has arisen very early in development,
but of which the cause is not apparent. In Fig. 3 is shown an
individual in which the arm opposite the madreporic plate is
forked or split longitudinally from the tip nearly to the disk.
This may be looked upon as a partial duplication or twinning
of this ray, or possibly as the result of early injury.

Fig. 4 shows a variation in which there are six perfect rays,
while in Fig. 5 there are seven. The six-rayed condition is much
less rare than the other cases enumerated. From a great num-
ber of specimens which Professor Verrill has examined from near
New Haven, Connecticut, 1 in about 2,000 has six rays, I in 3,000
has four rays, and I in 10,000 has seven or eight rays.t Some
of these may be due to repairs of injuries received in early life,
with development of extra rays.

The experimental studies of Dr. Helen D. King on the re-
generative processes in Asterias vulgaris} indicate the manner

*American Naturalist, 1909.
+ Loc. cit., p. 546.
t Archiv fiir Entwickelungsmechanik, vol. ix, 1900.

{
No. 19.] ECHINODERMS OF CONNECTICUT. 45

in which such variations may be artificially produced. For if
the disk of a starfish of this species be cut between the bases of
two of the rays by an incision reaching from the border of the
disk to the mouth, one or two new rays may sometimes be pro- '
duced in the healing of the wound. Such supernumerary rays are
at first smaller than the others, but it seems reasonable to assume
that by the compensatory regulations of the body they might
eventually become similar in all respects to the five original rays.
Some of the six- and seven-rayed individuals of the common star-
fish may have resulted from similar wounds inflicted by fishes or
by accident. In the removal of two or more rays, it sometimes
happens that the number regenerated is one less than the normal.
In this way a specimen like that shown in Fig. 1 may result.

In Fig. 6 is shown a specimen in which it is apparent that
some injury has deprived the animal of all its rays except one;
the four lost members are being regenerated in their normal
positions about the disk. It is not at all unusual to find in-
dividuals which are thus replacing one or more rays which have
been lost by an injury. Such regeneration can be studied ex-
perimentally in the laboratory, and is discussed in the following
chapter.

Nevertheless it should be emphasized that, while certain
species from other parts of the world naturally reproduce by
spontaneous division, it is not believed that our native species
can do so. As stated in the following chapter, a single ray
without any portion of the disk cannot reproduce the missing
parts, and there is good reason for believing that a large animal
with even one or two rays removed is often destroyed by its
enemies before regeneration has taken place. In smaller in-
dividuals the injury caused by amputation seems less serious.
But it is only when protected by favorable conditions that the in-
jured starfish survives in the struggle for existence.

REGENERATION

It is said that many years ago, when the starfish first began
to be recognized as an important enemy of the oyster, the oyster
fishermen sought to wreak vengeance on these devourers by taking
such as came into the boat with the oysters, tearing them into
two parts and throwing both parts overboard. In how large a
46 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [ Bull,

proportion of cases such a mutilation resulted in the death of
the starfish it is impossible to decide, but an examination of
any considerable number of specimens, especially of the common
starfish, Asterias forbesi, will show how futile are any efforts to
destroy the animal merely by tearing it in two, for many in-
dividuals will be found in the process of regenerating one or more
missing arms.

Such specimens indicate the readiness with which, under
favorable circumstances, the starfish may repair its injured
tissues, and replace one, two, three, or even four lost or muti-
lated arms. In fact, when carefully protected and fed in an
aquarium, the disk alone, deprived of all five arms, may slowly
regenerate all the missing parts.

If an arm be pulled forcibly from the disk, it often happens
that a portion of the disk is removed with the base of the arm.
If the arm be badly mutilated and not removed, it is usually
thrown off by the spasmodic contractions of the muscles at a
certain point immediately outside the disk. Very strong chemi-
cal or electrical stimuli may cause the same result.

This power of autotomy is doubtless of much importance to
the starfish, which can thereby stand a chance of escaping with
some of its arms when an enemy has seized one or more. Cer-
tain species living in other parts of the world,’ habitually re-
produce themselves by this method of fission, although none of
our native species multiply in this manner. In our species the
disk alone can restore the arms, but a single arm cannot restore
the disk.

Nevertheless it should be emphasized that whenever a star-
fish is mutilated from any cause it becomes at once more sus-
ceptible to the attacks of its enemies, the injured surface furnish-
ing a vulnerable point, from which the protruding soft tissues
may be seized by fishes, crustaceans, and other creatures. The
whole body may be destroyed before the wounded surface has
healed.

An arm removed from the body of a starfish may live for
several weeks if protected from the larger carnivorous animals,
but will eventually die without regenerating the rest of the body.

But the disk from which one or more arms are missing will,
if not destroyed by fishes or other enemies, immediately begin
No. 19.] ECHINODERMS OF CONNECTICUT. 47

the healing of the wounds and the regeneration of the missing
parts.

Careful observations on this point which have been made by
Mead* show how rapidly these regenerative processes may occur
in the common starfish.

The removal of a single arm has little if any influence on
the rate of growth of a young starfish, for such mutilated speci-
mens may grow as rapidly as normal individuals kept under
similar conditions. Futhermore the rate of growth of the re-
generating arm is on the average somewhat more rapid than that
of the remaining arms, so that there is a tendency to restore
the normal symmetry of the body. This is shown by the fact
that, of five individuals subjected to the experiment, the increase
‘in the length oi the largest arm in each during about eight weeks
was 8, 10, 10, II, and 10 mm., while the regenerating arm in
the same individuals grew 12, II, I2, II, and 9 mm., respectively,
in the same period.

The removal of two arms in a young starfish likewise has
little if any effect on the rate of growth when food is abundant.
In such cases also an accentuated growth in the regenerating
arms as compared with the others illustrates again the com-
pensatory properties of the body.

Although, as has been stated, it seems improbable that an
isolated arm can, in the common starfish, regenerate the missing
parts, yet the result is quite different if a small portion of the
disk is removed with the arm. In such cases, although growth
ceases for a long time, the normal body may eventually be
restored from the small portion of the disk remaining.

Furthermore it is often possible to cut the disk with its at-
tached arms into two or more pieces and from each piece obtain
a perfect starfish.

From such results it is conceivable that a starfish taken from
the water and torn roughly into two parts may, if a portion of
the disk remains attached to each part, eventually form two com-
plete animals by regeneration. That such an event is of usual
occurrence, however, is very improbable, because of the enemies
which may destroy the injured parts. It is far more likely that

 

* Bulletin U. S. Fish Commission, vol. xix, 1899-
48 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.

the part having the greater portion of the disk will quickly re-
generate its missing organs, while the other part will perish.

The regenerative capacity of the northern starfish, Asterias
vulgaris, has been the subject of an extensive series of ex-
periments by Dr. Helen D. King.* In this species, as in the
common starfish, a single arm without any portion of the disk
may live for several weeks, but is unable to reproduce the missing
parts of the body.

Of nearly two thousand individuals of this species examined,
about eleven per-cent showed one or more arms in process of
regeneration. In all cases except one the regeneration involved
the production of one or more new arms from the disk, and not
a repair of the injured tissues of an arm. It is thus assumed that
a badly injured arm is in nature thrown off and replaced by a
new one.

When the tip of an arm is removed, however, regeneration
of a new tip occurs, and the new eye-spot may be formed within
a week after the operation. The regeneration of a complete arm
from the disk requires several months.

When the arms are split longitudinally they are always
thrown off, except when the tip alone is split. In the latter case
two new tips may develop, giving a forked extremity to the arm.
Oblique cuts and the removal of small pieces result in the normal
regeneration of the injured tissues. The wounds made by cut-
ting the disk may lead to the formation of supernumerary arms,
as described in the preceding chapter.

REPRODUCTION

The starfishes are of separate sexes, although there are no
external characters by which the sex is indicated.

One of the chief reasons why the starfish occurs in such
enormous numbers, is found in the immense number of eggs
produced by a single femiale. The animals are capable of breed-
ing, as has been recently found by Mead, if the food supply is
abundant, when but one year old. As the animal increases in
size during succeeding years, an increasing number of eggs or
sperm cells are produced annually.

* Archiv fiir Entwickelungsmechanik, vol. ix, pp. 724-737, 1900.
v
No. 19.] ECHINODERMS OF CONNECTICUT. 49

The sexual glands vary greatly in size according to the de-
gree of maturity of the sexual products. They are voluminous,
as shown on Plate V, and occupy, when mature, much of the
space within the body walls. The number of eggs produced by
a single individual in one year varies with the size of the animal,
and is also largely dependent upon the previous food supply.

The genital organs develop in intimate relation with the
tissues adjacent to the madreporic canal. When fully formed they
consist of five pairs of voluminous feather-like bodies situated
in the interradial spaces of the body, and extending freely
into the arms, as shown in Plate V. Each gland opens to
the exterior by a minute pore on the aboral surface near the
base of the corresponding side of an arm.

When the sexual products are fully ripe, the eggs of the
female pass out of the genital pores and float about in the water
or sink slowly to the bottom.

The males at the same season discharge from similar open-
ings milky clouds containing millions of minute sperm cells.
Each of these sperm cells is provided with a vibratile tail, by
means of which it swims about in the water. Whenever one
of these sperm cells comes in contact with an egg recently
discharged from the female, it bores its way into the substance
of the egg, and fertilization results. Only a single sperm cell
normally enters an egg; if others approach, their entrance into
the egg is usually inhibited. If more than one actually succeeds
in penetrating the egg substance, abnormal development occurs.
Such eggs as are not fertilized within a short time after being
deposited perish.

After fertilization a series of internal changes occurs re-
sulting in the fusion of the nuclei of egg and sperm. The
processes of cleavage and embryonic development then ensue,
as described in the following chapter.

The season at which the sexual products are matured in
Long Island Sound varies considerably with different individuals.
When examined in the fall the sexual glands of all the small
individuals and of many of the larger specimens are small and
inconspicuous. During the winter they increase in volume and
by early spring have attained nearly full size. Their feather-like
processes then extend far out into the cavities of the arms, and

4
50 CONNECTICUT GEOL, AND NAT. HIST. SURVEY. [Bull.,

they have taken on a rosy color characteristic of approaching
maturity. Yet, in spite of the apparent ripeness of the sexual
glands, the sperm cells of many individuals lack the activity of
full development, and the eggs of the females when examined
. under the microscope reveal their immaturity.

In May the sexual glands have become so greatly distended
in well-fed individuals that the arms appear full and rounded.
The feather-like processes of the glands have now become so
delicate that a slight injury is sufficient to allow the sexual
products, eggs or sperm cells, according to the sex of the in-
dividual, to flow out freely into the water. From this time on
through the following month the eggs of a majority of speci-
mens can be easily fertilized artificially, and make extremely
interesting objects for the study of cleavage and early develop-
ment. Owing to the minuteness of the sexual products, how-
ever, a compound microscope is necessary for the study.

To obtain the eggs for study plenty of clean sea water must be
at hand together with suitable receptacles of glass or porcelain.
Soup dishes or common tumblers are very convenient, but
must be kept covered. The starfishes must, of course, be kept
alive in sea water, and in order to insure ripe products of both
sexes a considerable number of specimens should be available.

After placing clean sea water in one of the vessels a starfish
may be taken and, by means of strong scissors, opened by re-
moving the aboral surface of one or more of the arms. The
feather-like glands may be taken with a pair of forceps and
shaken gently in the vessel of water. A milky cloud issuing
from the cut end of the gland indicates that the specimen is a
male, the cloud itself being made up of thousands or millions of
sperm cells. If, on the other hand, instead of a milky cloud,
there issues a stream of tiny particles barely visible to the naked
eye, the animal opened is a female, and the little particles are
the eggs, or ova. Examination of a drop of the contents of
the vessel under a microscope will prove definitively which sex
has been obtained. One or more other starfishes must be opened
in a similar manner, the generative products of each being re-
ceived in a separate vessel, until the genital products of both
sexes have been obtained.

After the eggs in one of the vessels have settled to the
No. 19.] ECHINODERMS OF CONNECTICUT. 51

bottom, the greater part of the water should be poured off and
be replaced by clean water. No more eggs should be left in
the vessel than will cover the bottom in a single layer. A drop
or two of the water in a vessel containing the sperm should
now be added to the eggs, and will probably contain a sufficient
number of sperm cells to fertilize all the eggs present.

Within an hour and a half after fertilization, the eggs, which
should be examined from time to time under the microscope,
will have divided into two cells. The four-, eight-, twelve-, and
sixteen-celled stages follow rapidly, and resemble the cleavage
stages of the sea-urchin shown in Fig. 15.

In about twelve hours more, if the’ temperature is fairly
warm, free-swimming ciliated embryos will be found. Ifa few
embryos are kept in plenty of clean, cool sea water, they will
live for several days and develop into the so-called brachiolaria
stage, as shown in Fig. 4.“

Under the normal conditions of the sea, the free-swimming
stages last about three or four weeks, after which such larve
as have survived settle to the bottom and attach themselves to
rocks, seaweeds, eelgrass, or other objects, and by a complicated
metamorphosis become transformed into tiny starfishes.

As has been stated above, the majority of individuals of the
common starfish mature their genital products in May and June,
and discharge them into the water during the latter month.
There is, however, great individual variation in this respect, for
an examination of a large number of specimens at any season
of the year, even in the fall, will show some in which the genital
glands are large and contain ripe or nearly ripe sexual products.
Furthermore, during the months immediately following the nor-
mal spawning season there are some individuals which are filled
with mature genital glands. Such individuals apparently repre-
sent instances of belated maturity of the sex products, or those
which for some reason have failed to discharge their ripened
germ cells at the normal time.

Such individuals, however, probably have little influence in
propagating the species; for, even if their sexual products are
discharged into the water, there is very little chance that fertiliza-
tion can occur at other times than in the normal spawning season,
when the water is swarming with the germ cells of both sexes.
52 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. { Bull.

Because of the vastness of the volume of the surrounding sea
water it is only when both sexes discharge their products within
reasonable proximity to each other and at very nearly the same
time that the eggs have any chance of being met by the sperm
cells. Nevertheless, under favorable conditions of currents in
the water, the sperm cells may be carried to eggs deposited
at some considerable distance, probably several hundred feet.

Except in rare instances, therefore, such individuals as fail
to mature their sexual cells at the normal period and discharge
them into the water in the vicinity of one or more individuals
of the opposite sex give rise to no offspring during that season.
Moreover, it is uncertain as to whether such sexual products
as mature at unusual seasons are discharged from the body.

The northern starfish, Asterias vulgaris, exhibits breeding
habits similar to those described for the common starfish. In
this species also the sexual products mature in summer.

The breeding habits of the blood starfish (Henricia) differ
widely from those of the two preceding species of Asterias,
in that there is no free-swimming larval stage. The eggs of
this species are large and heavy, being filled with an orange-
colored yolk. But few eggs are produced by each female. They
give rise to embryos which pass though an abbreviated larval
development, and quickly assume the form of the adult. Fisher
has recently described* the brooding of the eggs in the case of
one of the Pacific coast varieties of this species. The brood pouch
is formed by arching the disk and bringing the bases of the rays
close together. Into this cavity the eggs are tightly packed, and
the developing young are thus protected by the mother until after
the adult form has been reached.

The slender-armed starfish (Asterias tenera) is stated to
brood its eggs and developing young in the same manner.

DEVELOPMENT

Common Starfish.— The eggs of the common starfish, as
stated in the preceding chapter, are set free in the surrounding
sea water mainly during the month of June. The developmental
processes are very complicated, and many of the details are not

*U. S. National Museum, Bull. 76, p. 277, 1911.
No. 10.] ECHINODERMS OF CONNECTICUT. 53

yet well understood. A general account of the larval stages is
given in the earlier papers by Agassiz,* and by Mead.t

The eggs fall to the bottom, and after fertilization the pro-
cess of cleavage takes place, as described for the egg of the sea-
urchin (page 100). In about twelve hours the substance of the
egg has been subdivided into hundreds of cells which arrange
themselves to form the body of an embryo. The surface of the
body becomes covered with hair-like processes, termed cilia,
which are kept in constant vibration and enable the embryo to
leave the bottom and swim free in the water.

The body of the embryo becomes further differentiated, and
a mouth, digestive system, and other organs are formed. The
embryo can now take into its body still smaller organisms than
itself for food, and under favorable conditions increases rapidly
in size. Meanwhile the rounded shape of the body has changed
into a structure with a number of projecting lobes covered with
very long cilia, and the embryo is now termed a bipinnaria.
In this stage the embryos are very sensitive to light and at-
mospheric conditions, and collect in vast swarms which at times
float near the surface and at other times sink deeper into the
water. They may be carried back and forth by the tides, winds,
and currents, and become widely separated from their birthplace.
They have a considerable power of locomotion, but do not swim
for a long time in any given direction.

By further modifications the embryo develops into the strange-
looking, transparent creature shown in Figs. 4 and 5. In this
stage, known as the brachiolaria, the body is provided with
several pairs of long arms covered with vibratile cilia. As the
brachiolaria bears no resemblance whatever to the adult star-
fish, naturalists for a long time supposed it to be an entirely
different kind of animal. And yet from such a creature the
young starfish develops by a complicated metamorphosis.

After swimming about in the water for some three or four
weeks, depending largely upon temperature and other external
conditions, the larva becomes full-grown, and the brachiolaria

*On the Embryology of Echinoderms. Proceedings Am. Acad., 1863; and Mem.
Am. Acad., 1864. North American Starfishes. Mem. Museum of Comparative
Zoélogy, 1877.

{ The Natural History of the Starfish. Bull. U. S. Fish Commission for 1899.
54 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. {Bull.

is now some fifty times as large as the original embryo. It is
now ready for the metamorphosis.

    

Fic. 4. Free-swimming
larva (Brachiolaria) of
starfish. (After Weysse.)

Fic. 5. Free-swimming larva (Brachio-

The wavy disk-like area .
sé the lowet end of figure laria) of starfish. (After Mead.)

represents the portion of The stippled areas in the central and
the body which will remain lower parts of the figure indicate the posi-
after the transformation to tion of the digestive tract, the mouth be-
the adult stage. Compare ing shown at the left-hand edge of the
Figs. 5 and 6. figure, with the intestinal opening below.

The external changes by which the metamorphosis is ac-
complished, and the habits of the young starfish, are described by
Mead* as follows:

“Already the rudiment of the resulting starfish can be seen
within the brachiolarian. The five crenate lobes on the margin
of the disk are the beginning of the five arms. The disk itself
at this time is already somewhat opaque.

“When the larva is about to ‘set,’ it attaches itself to some
object, like a spear of eelgrass, by the suckers, shown at the

top of the figure (Figs. 4 and 5), and then a rapid transformation

* Bull. U. S. Fish Commission for 1899.
No. i9.] ECHINODERMS OF CONNECTICUT. 55

occurs. The whole superstructure above the disk collapses and
becomes absorbed like the tail of a tadpole. In a few hours the
brachiolarian has disappeared, and a starfish proper (Fig. 6) has.
taken its place.

 

Fic. 6. Aboral surface of star-
fish shortly after the metamor-
phosis. (After Brooks.)

“Up to the very time when the larve are ready to set they
swim freely in the water; and larve, caught in the tow-net,
often set in the dish of water before I had returned to the house-
boat, 7. e., within an hour of the time they were caught. In
this condition they attach themselves by their suckers to any
object they happen to strike, and cling to it with great tenacity
until the metamorphosis is completed. As the larve are borne
along by the currents, the eelgrass, rockweed, and especially
the fluffy, branching seaweed, naturally catch immense numbers
of them. I think it would not be an exaggeration to say that on
a single handful of seaweed which I picked up about the first
of July there were more than a thousand young stars. For the
next three weeks they remain for the most part crawling about
over this vegetation, gradually working down among the roots of
the rockweed and upon the large stones at the bottom. They grow
rapidly during this time, but decrease in numbers, for they are
bright and conspicuous objects for the small fishes; yet they
are exceedingly numerous for a long time. In order to obtain
a definite expression of their abundance, I scooped up a large
handful of the fluffy seaweed, which, together with the water,
filled about two-thirds of a paper pail, and from this 603 young
56 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. {Bull.

stars were taken. A cart-load of seaweed taken out at this time
would have destroyed millions of starfish,

“By the first of August the fluffy, branching seaweed, which
bore so many young stars, was nearly all dead, and though the
stars were still present in great numbers upon the eelgrass, rock-
weed, and stones covered with sea-moss, they were also
frequently seen crawling along the muddy bottom. By August
15 the eelgrass was overgrown and lodged by a luxuriant
growth of Boéryllus, a compound ascidian, which appears as
dark gelatinous patches. The small stars were still numerous
upon it, but were rather thin and poor. The larger and better
nourished stars had left the eelgrass and were searching for
food upon the stones and along the bottom.

“The small starfishes, such as live upon the eelgrass, are re-
markably hardy in some respects. They will live for weeks, and
even months, in a small dish, without change of water and with
a minimum amount of food. During the'first week in July I
carried a number of free-swimming brachiolaria to Providence
for further examination. They were in a glass I-quart jar, and,
after one or two were taken out, the jar was closed and was left
unopened during the rest of the summer. In a few days the
larve had all set, and when I examined the dish again, on Sep-
tember 5, it contained still a few live stars, which were, how-
ever, very small. Upon watching them it was seen that the
more enterprising individuals were eating their companions, and
finally only one remained. This one lived in the jar for weeks,
but, unfortunately, I am not able to record the exact date of
his death.

“On the other hand, the same young starfishes, which can
live so long without food or change of water, perish quickly
if left out of the water, especially if the sun is shining. They
cannot live, therefore, above the low-water mark, unless sheltered
‘by a dense growth of vegetation. Large stars can endure very
much longer exposure, since their bulk prevents their drying
so quickly. On July 16 I made a special search for young
stars on the seaweed, above the low-water mark. I found none,
yet just below low-water mark they were excessively abundant.
At the same time it was noticed that above the line where the
starfish were abundant there was a thick set of 1-year-old oysters,
No. 19.] ECHINODERMS OF CONNECTICUT. 57

while below it the oysters were absent. The oysters set some-
what later in the season than the starfish, and the latter, there-
fore, are ready to prey upon the young oysters as soon as they
appear. When, in addition to these facts, we take into account
the extraordinary voracity of the young starfish, their immense
numbers, and their special fondness for oysters, we are led to
conclude that one reason why a considerable set of oysters is so
rarely obtained below low water is that they fall prey to the
starfish. The'oysters which set above low water are comparatively
safe, for when the tide leaves them uncovered they can endure
for hours the direct heat of the sun, which would kill the young
Starfish in a few minutes.

“ While the starfish are living upon the eelgrass and seaweed
they are supplied with an abundance of food in the form of the
young of marine worms, snails, and other animals, which, like
the stars themselves, swim freely in the sea for a time, and then
settle down upon any object with which they happen to come in
contact. Throughout July the water at Kickemuit was teeming
with minute free-swimming creatures, and in the aquarium the
growth of the youngest stars could be greatly accelerated by feed-
ing them the contents of the tow-net. During the last four days
of June innumerable larve of a marine worm (Syllis) were
swarming at the surface, and on July 11 millions of the young
of one of the sea snails (Littorina?) were caught in the tow-nets.

“The clam, also, is one of those unfortunate animals whose
larve set at about the same time as the starfish, and in the same
places. The starfish before they are three days old show a predi-
lection for young clams, which apparently does not diminish so
long’ as any clams remain.”

In Fig. 7 one of these young starfish is shown in the act of
devouring a small clam. A single young starfish has been known
to devour as many as 56 small clams within a period of six days.

“From the foregoing it appears that the starfish set for the
most part during the last few days in June and the first week
in July, some as late as July 16. They remain upon the seaweed
in immense numbers until about the Ist of August, when many
of them are found upon the bottom. By August 15 the greater
portion of the stars have left the seaweed and gone to the bottom.
i

58 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.

“The stars could be destroyed by hundreds of thousands in
July by collecting and drying a few cartloads of seaweed taken
below low-water mark. After the first week or two of July the
collection of seaweed would do no injury to the clams.”

 

Fic. 7. Very young starfish in the
act of devouring a mollusk. (After
Mead.)

The rate of growth of the young starfish is discussed on page
40.

Northern Starfish. — The larval stages of the northern starfish
have been studied by Agassiz*, Fieldt, and others, while Goto}
has made detailed investigations on the metamorphosis. Accord-
ing to these observations the development of this species is similar
to that described for the common starfish.

Slender-armed Starfish.—- This species is reported as pro-
ducing a small number of comparatively large eggs, which develop
without free-swimming stages. It is also said to protect its
eggs and embryos beneath the peristome until the young star-
fishes have reached a diameter of several millimeters.

Blood Starfish. — In this species only a few large eggs are
produced. These develop into the adult form by a complicated
metamorphosis, although, as stated on page 52, the larve do not
swim free in the water.

‘KEY TO SPECIES

The starfishes of the world may be divided into five orders,
only two of which are found in Connecticut waters or in their
*Mem, Museum Comparative Zoélogy, 1877.

+ Quarterly Journ. of Microscopical Science, 1892.
LJourn. College of Science, Imp. Univ. Tokio, 1898. ¢

%
No. 109.] ECHINODERMS OF CONNECTICUT. 59

vicinity. The order Spinulosa, represented by the beautiful little

blood starfish, Henricia sanguinolenta, includes the more primi-

tive forms, in which the disk and rays are everywhere thickly

covered with minute spines, but there are no pedicellarie. In

this order there are but two rows of tube-feet. The order Forcip-

ulata includes our three species of Asterias. In this order the

disk and rays have scattered coarse spines, and very numerous
pedicellariz. There are usually four rows of tube-feet.

Our native species may be distinguished by the following

characters:

1. Disk and rays comparatively smooth, covered with minute,

closely set spines; pedicellarize absent; tube-feet in two

POW! Shivsesxe igs Sistocedigiee sna aed nui eas Henricia sanguinolenta

Disk and rays rough, with coarse spines; forceps-like pedi-

cellarize abundant; tube-feet in four rows............. 2

2. Rays nearly cylindrical, tapering and slender; spines very

numerous, slender, sharply pointed, usually surrounded

with a broad wreath of small pedicellarie...............

Asterias tenera

Rays broad, somewhat flattened; spines thick and blunt....3

3. Rays blunt at the ends; skeleton quite firm; spines scattered ;

pedicellarize near ambulacral grooves short and broad;

madreporic plate usually orange........ Asterias forbesi

Rays pointed at the ends; skeleton rather soft; spines scat-

tered, but often forming a rather distinct median longi-

tudinal row on the aboral side of each ray; pedicellariz

near ambulacral grooves slender; madreporic plate pale

VON OW ossiicced sea yh bime etaeeSetng GecKees Asterias vulgaris

Asterias forbesi (Desor)
Common. Starfish

Plate I, fig. 4; Plates II, III, IV, VI, VII, VIII.

This well-known pest of the oyster is found along the Atlantic
coast from the Gulf of Mexico to Maine, and is the only species
of starfish which is common in the greater portion of Long Island
Sound.

The species is so generally distributed in the Sound that the
mention of specific localities would be superfluous. As a rule it
60 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. (Bull.

is most abundant on shelly bottoms in shallow water. In the
fall the tide pools in rocky localities along the shore are often
crowded with young starfishes measuring from a half-inch to
three inches between tips of opposite arms. These are feeding on
the barnacles and young oysters which are attached to the rocks.
At the approach of winter most of the starfish leave the shore and
migrate into deeper water.

In spite of the thousands of bushels of these starfishes which
are annually destroyed by the oyster growers there seems to be
no diminution in their numbers except in restricted localities.

The size of average mature individuals of this species is from
four to six inches between the tips of the opposite arms, but
much larger individuals are sometimes found. The variation in
the number of rays is discussed on page 43. The shape of the
rays depends somewhat on the state of contraction of the ambu-
lacral groove, and varies with the state of development of the
sexual glands and the general nutrition of the body. In general
(as shown on Plates II, III, IV, and VIII) they are thick and
stout, with blunt and rounded tips.

Individuals of this species can usually be distinguished from
those of Asterias vulgaris by the difference in the proportions of
the rays, as shown on Plate VIII. The latter species usually has
more slender and pointed rays, while those of the common star-
fish are comparatively thick and blunt.

The coloration of this species is subject to great variation, the
most common shades being greenish or brownish green, with
light yellow spines and orange-red madreporic plate. The colors
of other specimens range through brown, bronze, orange, and
purple. There seems to be little if any correlation between the
color of the animal and the age, sex, or environment, although in

 

EXPLANATION oF Piate VIII. Upper figure, Asterias forbesi. Three-
fourths natural size. Lower figure, Asterias vulgaris. One-half
natural size,

Photographs of dried skeletons from oral surface, to show the dif-
ferent proportions of the arms in the two species. The skin, tube-feet
and other soft parts have been removed. Around the mouth may be
seen in each figure five groups of large spines, the oral spines, or mouth

papille. In the upper specimen the oral spines lie in the positions they |

occupy when the mouth is closed, while in the other specimen the mouth

is fully opened. The ambulacral grooves are widely opened, and show’
the four rows of openings for the tube-feet in each groove. (From |.

photographs loaned by Prof. A. E. Verrill.)
Missing Page
Missing Page
No. 19.] ECHINODERMS OF CONNECTICUT. 61

restricted localities a definite color variety may predominate.
After death the body assumes a dull reddish or orange color, and
the madreporic plate is yellow or brown.

The plates of the aboral surface bear numerous blunt spines
surrounded by circles of pedicellarie (Plate III). The respira-
tory papulz, or branchiz, are grouped in clusters of four to six
or more in large areas between the spines. Each of the plates
adjacent to the ambulacral grooves bears usually two slender,
flattened, sharply truncated spines. The number of such plates
increases with the growth of the animal, being from 80 to 120
in well grown individuals.

A full and interesting account of the habits and life history
of this species is given by Mead, in the Bulletin of the U. S. Fish
Commission for 1899.

Asterias vulgaris Verrill

Northern Starfish
Plates V, VIII, IX.

Although this species is found in the colder waters of the
eastern: part of the Sound, its more usual habitat is farther to
the northward. It is occasionally found as far west as Faulk-
ner’s Island and the Thimble Islands, but becomes more common
from New London eastward, particularly in the deeper and colder
waters.

This is the common starfish north of Cape Cod, and ranges
northward to the coast of Labrador. In the deeper, colder waters
off the Atlantic coast the species extends south as far as Cape
Hatteras. In certain localities, as at Woods Hole, Mass., Narra-
gansett Bay, and the eastern part of Long Island Sound, this
species is sometimes associated with the common starfish. The
same or a very similar species occurs on the coast of Europe,
where it is known as Asterias rubens.

 

 

EXPLANATION oF Pirate IX. Asterias vulgaris. About one-half natural
size.

Photographs of living individuals, from aboral and oral surfaces.
In the upper figure the disk is somewhat unusually swollen. The lower
figure shows the four rows of tube-feet and the mouth. These figures
well illustrate the characteristic arrangement of the spines on both surfaces
of the body. . _. ; “
(Photographs loaned by the U. S. Fish Commission, with permission

of Dr. H. L. Clark.)
62 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.

In general it is possible to distinguish our two species by the
shape of the body, the arms being thicker at the base and more
pointed at the tips in the northern starfish (Plates VIII, IX),
while those of the common starfish are rounded and blunt at the
tip. The spines along the middle of the aboral surface of each
arm often form a conspicuous median row (Plate IX) extend-
ing the length of the arm, while those of the common starfish are
scattered more irregularly.

Another specific distinction may be found in the shape of
the major pedicellariz, particularly those on the adambulacral
spines, as shown in Fig. 8. Instead of the broad, rounded
pedicellariz found in A. forbesi, many of those of the present
species have long and pointed blades.

 

Fic. 8, Calcareous plates of pedicellarie of Asterias. A, major
pedicellaria, oa vulgaris; B, minor ee A. tenera; C, major
pedicellaria, A. forbesi; D, minor pedicellaria, A. forbesi. All from
adambulacral spines. Enlarged go diameters.

This species grows to a much larger size than does the com-
mon starfish, full-grown individuals often measuring eight inches
or more between the tips of opposite arms. Specimens more
than 16 inches in diameter have been recorded from Nova.
Scotia.

The coloration shows great variation, yellow, yellowish brown,
orange, and purplish specimens being most abundant, although
shades of pink and red are sometimes present. The madreporic
plate is usually pale yellow. The spines are generally of lighter
color than the surface of the body.
PLATE X. Slender-armed Starfish, Asferzas tenera.

 
No. 19.] ECHINODERMS OF CONNECTICUT. 63

Asterias tenera Stimpson

Slender-armed Starfish
Plate X.

In the paper by Stimpson* in which the original description
of Asterias tenera occurs, there is described another, very similar
species, under the name of A. compta, based on a single specimen
three inches in diameter.

Asterias compta was thought to differ from A. tenera in
being of somewhat less slender proportions, in having the rays
more depressed, and particularly in having the spines, especially
towards the tip of the rays, surrounded by broad wreaths of
pedicellariz. The type locality for A. tenera was Massachusetts
Bay, and for A. compta off the coast of New Jersey.

From an examination of the records of the collections of
this species by the United States Fish Commission, Verrillt gives
the distribution of 4. tenera as Cape Cod to Newfoundland in
1o to 129 fathoms, and states that the species is abundant in
Massachusetts Bay and the Bay of Fundy in 10 to 40 fathoms.

Verrill states that A. compta is large and abundant in the
cold area south of Rhode Island and Marthas Vineyard in 20
to 50 fathoms. He emphasizes the close relationship of the two
so-called species, and suggests that A. tenera may be only a
poorly nourished, slender variety of A. compta. Clarkt has
examined both varieties and considers them specifically identical.

An examination of a large number of specimens of both
forms belonging to the Yale University Museum has failed to
show any definite anatomical characters by which they can be
invariably distinguished. Many of the specimens can be placed
without hesitation in the one group or the other, but others, and

 

* Proc. Boston Soc. Nat. Hist., pp. 269, 270, 1862.

¢ Distribution of the Echinoderms of Northeastern America. Am. Journ. Science,
vol. xlix, 1895.

+ Bull. U. S. Fish Commission, 1902.

 

 

EXPLANATION OF PLateE X. AsSterias tenera.

Fig. 1. Oral surface of dried specimen showing the slender spines sur-
rounded by dense wreaths of pedicellarie; about twice natural
Size,

Fig. 2. Aboral surface; natural size. ; ;

Fig. 3. Oral surface of a small specimen preserved in alcohol, showing
the broad ambulacral grooves with tube-feet; natural size.

Fig. 4. Oral surface of dried specimen; natural size.
64 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.

particularly the smaller specimens, possess such intermediate
characters that it has been found impossible to place them in
either group. Therefore but a single species can be recognized
at present, and, as the description of A. tenera precedes that of
A. compta by a single page, the former has priority.

On the coast of Europe occurs a very similar species,
A, Miilleri, and it is not certain that this is specifically distinct
from our A. tenera. Further examination of a large series of
both forms is needed to determine the matter with certainty.

Asterias tenera, including both varieties, as shown by the
records of the U. S. Fish Commission, ranges from off the mouth
of Chesapeake Bay northward to Nova Scotia, in from I0 to 129
fathoms. It is recorded from the eastern end of Long Island
Sound, off Watch Hill, Rhode Island, but is more abundant in
the colder water farther off the coast and to the northward.

‘The individuals of this species are small in size. Mature
specimens commonly measure only from two and one-half to four
inches between the tips of opposite arms. A few larger spec-
imens have been obtained, but the vast majority of specimens in
the extensive series belonging to the Yale University Museum
are less than three inches in diameter.

The species may be distinguished from our other species of
the genus by the nearly cylindrical, slender, pointed arms
(Plate X). The disk is small, the slender arms being from five
and one-half to seven times as long as the diameter of disk.

The color in life is pale, sometimes nearly white; often pale
purplish or pinkish. The madreporic plate and the spines are
whitish.

The rather open meshwork of plates on the aboral surface
carries very prominent, slender spines (Plate X, fig. 2) which
do not form a clearly defined median row on the arms, as they
do in Asterias vulgaris. In the majority of specimens all the
spines except those on the disk are surrounded by a conspicuous
wreath of pedicellarie (Plate X, figs. 1 and 4). They are more
closely crowded toward the tip of the ray. In some individuals
pedicellariz occur upon the spines of the disk, while in others
they are almost entirely limited to the rays. Usually one, two,
 

PLATE XI,

Midi aire snialet®

ident

iy

 

Blood Starfish, Henricza sanguinolenta.
No. 19.] ECHINODERMS OF CONNECTICUT. 65

or a few much larger pedicellarize are found on the oral surface
of the disk in each of the angles between the rays,

When the spines of the disk are free from pedicellariz, groups
of such organs appear at the beginning of the rays near the
bases of the spines, and these groups develop into conspicuous
wreaths on the more prominent spines of the rays. The wreaths
are most conspicuous on the large spines about the ambulacral
grooves and toward the tip of the rays (Plate X, fig. 1).

The individual pedicellariz in these wreaths, while relatively
large as compared with the size of the spine, are much smaller
than in our two other species of the genus (Fig. 8). They are
usually oval in outline, with rather blunt points.

The madreporic plate is small, and provided with a few very
wide furrows.

The branchie are usually separate or in groups of two in
each branchial area.

As is the case with several other species of the genus, this
little starfish protects its eggs and young beneath the disk, and
carries about with it the young clinging to the partially everted
borders of the mouth.

Henricia sanguinolenta (O. F. Miller)

Blood Starfish
Plate I, figs. 1— 3; Plate XI.

This beautiful little starfish is known in the writings of most
American zodlogists by the name of Cribrella sanguinolenta. It
has recently been shown, however, that the generic name Hen-
ricia must take precedence over the more familiar Cribrella.

Like the preceding species, this is more properly a northern
form, and grows far more abundantly and of larger size along
the coasts of Maine and Labrador than farther south. It occurs,
however, in the cold, deep water off our coast as far south as
Cape Hatteras, and has been taken at a depth of more than a
thousand fathoms.

 

 

EXPLANATION oF Prate XI. Henricia sanguinolenta. : ;

.. Fig. 1. Aboral surface of disk, showing madreporic plate, intestinal
opening, and arrangement of spines; three times natural size,

Figs. 2 and 3. Aboral and oral surfaces: about two-thirds natural size.

Fig. 4. Oral surface of dried specimen; slightly enlarged.

5 ,
66 CONNECTICUT GEOL, AND NAT. HIST. SURVEY. [ Bult.

To the northward it extends not only along the Atlantic
coast of North America but also to Greenland, and is found also
on the northern coasts of Europe and Asia. It occurs from the
Azores to the British Islands, Scandinavia, and Spitzbergen, and
along the shores of the Arctic Ocean to Bering Strait. On the
American side of the Pacific Ocean the species: extends as far
south as Washington, and on the Asiatic side southward to
the Kurile Islands. This would indicate a typical circumpolar
species which extends southward along the continental shores to
latitude 38° to 48° N.

In Long Island Sound the blood starfish appears to be limited
to the eastern part, which has deeper and colder water than is
found elsewhere. It extends at least as far west as New London.

It is at once distinguished from our species of Asterias by
having only two rows of tube-feet beneath each arm, arranged
in a single row along each side of the narrow ambulacral groove
(Plate XI). The proportions of the body vary greatly, as shown
on Plate J. The arms are either rounded or flattened at the base,

‘but are always rounded or nearly cylindrical distally, and are
comparatively slender and acutely pointed (Plate I). In some
specimens (Plate XI) the arms are swollen near the base, and
sharply contracted between base and disk. Sometimes the tips
of the arms are slightly raised and curved aborally, and the two
arms of the bivium are brought closer together than are any of
the others (Plate XI). :

The aboral surface lacks the prominent spines of Asterias,
the whole surface being comparatively smooth, but actually
covered everywhere with minute closely set spines (Plates I
and XI).

The branchiz are usually scattered singly in minute spaces
between the thickly placed spines. The madreporic plate is small,
and marked by a few broad grooves. The anal opening is more
conspicuous than in Asterias (Plate XI, fig. 1).

Specimens from Long Island Sound rarely exceed three or
four inches between the tips of opposite arms.

The colors are unusually deep and bright, rendering the
animal very conspicuous when exposed to full view. The usual-
color is bright red or orange on the aboral surface, although
cream-colored, yellow, pink, lavender, and purple specimens are
Missing Page
No. 19.] ECHINODERMS OF CONNECTICUT. 67

sometimes found. Occasionally the surface is mottled red and
purple. It has been said that a glass dish filled with these star-
fishes might vie with a tulip bed in gaiety and vividness of tints.
The oral surface is deep yellow.

The ‘few large eggs laid by each female in early spring
develop by a complicated metamorphosis, but the adult condition
is reached without passing through a free-swimming stage. In
this species the eggs and young are protected beneath the disk
of the mother.

Class 2. OPHIUROIDEA

The representatives of this class are known popularly as
serpent stars, snake stars, brittle stars or sand stars. The
species which occur in the waters of Long Island Sound are small
and inconspicuous as compared with the common starfish or
the sea-urchin, and are seldom noticed by the ordinary visitor to
the seashore. They are protectively colored, so that it is very
easy to overlook them when their slender arms are stretched
out among the roots of the eelgrass or coiled up in crevices of
rocks. Furthermore they are of a retiring disposition and largely
nocturnal in. their habits, remaining secluded as much as possible
during the daytime. Some forms live beneath stones or hidden
among seaweeds in small crevices of the rocks. One species,
Amphioplus abditus, lives buried in the mud, with one or more
arms projecting above the surface. It is only when they are
disturbed and are moving their delicate arms in an effort to
escape that they are at all likely to attract the attention even of
a trained observer. And, finally, although they occur in great
abundance in certain localities, in most places they are so scarce or
so well protected by their habits and coloration that careful
search for hours at a favorable tide will fail to disclose a single
specimen.

 

 

ExpLaNnation or Piate XII. Variation,- Ophiopholis aculeata.

Photographs of five individuals to show some of the variations in form,
length of arms, and color patterns of this extremely variable species.
These figures represent but a few of the innumerable positions which the
arms can assume in the living animal. In the upper left-hand figure all
the on are in process of regeneration, (All figures three-fourths natural
size.
68 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [ Bull.

STRUCTURE

The class Ophiuroidea contains hundreds of species distrib-
uted all over the world. Four of these species are known to
occur in Long Island Sound, and one other has been found so
near the eastern entrance to the Sound that it seems probable
that further investigation will reveal its presence in Connecticut
waters.

They all have a flattened, circular or pentagonal body, called
the disk, with five very slender, flexible, jointed arms, or rays
(Plate XII). These arms taper gradually toward the tip, and
their movements in life are such as to warrant the popular
appellation, “serpent stars,” for, when the animal is disturbed,
each one twists in all directions and folds itself about adjacent
objects in a truly serpentine fashion.

The mouth is placed in the center of the disk, in a position
similar to that in the starfish. Hence the side of the disk con-
taining the mouth and the corresponding faces of the arms make
up the oral surface, while the opposite side of the disk and arms
is the aboral surface. The mouth is provided with five triangular
jaws, each situated between a pair of arms, that is, in one of
the interradial spaces (Plate XIII).

The arms are distinctly marked off from the disk, and do
not pass gradually into it like those of the starfish. Ambulacral
grooves are wanting, and the tube-feet are very delicate.

The disk contains all the digestive and reproductive organs,
the arms containing only a row of calcareous ambulacral ossicles

 

 

EXPLANATION OF PraTeE XIII. Skeleton of Ophiuran. Ophiopholis
aculeata. (Four times natural size.)

Photographs of disk and bases of rays from oral and aboral surfaces
to show characteristic arrangement of plates. The upper figure shows the
granulations and very blunt spines which cover many of the plates of the
disk, leaving only about forty of the plates exposed. In many specimens
the number of exposed plates is smaller; sometimes as few as six are thus
left bare. These exposed plates are usually grouped symmetrically in the
five radial and five interradial areas, with a single plate in the center of
the disk. The upper arm plates are seen to be separated by a row of
plate-like granules.

The lower figure shows the five jaws, with four scale-like projections,
oral papillz, on each side of each jaw. In the interradial areas are five
large plates, oral shields. It will be noticed that the oral shield between
the arms nearest the top of the page is larger than any of the other four,
and forms the madreporic plate. On each side of the ventral arm plates
is a single row of flattened spines, the tentacle scales.
 

 

 

 

 

. let n of Ophiuran ‘
’ Ophiopholts i
s sj aculeata. ( Four times natural
No. 19.] ECHINODERMS OF CONNECTICUT. 69

with a slender branch of the body cavity, together with small
nerves and branches of the water-vascular system.

The mouth leads into a narrow esophagus, and this opens
into a large saccular stomach, which fills up most of the space
within the disk. There is no anal opening, the indigestible
remains of the food being cast out of the mouth.

Disk.— The disk is covered with thin plates on all sides.
Certain of these plates present such definiteness in form and
arrangement that they afford the most convenient characters for
distinguishing the various species.

On the oral surface five triangular groups of plates project
in toward the center of the disk and form the jaws (Plate XIII).
The j jaws are usually provided with numerous toothlike processes
or flattened scales constituting the masticatory apparatus. These
processes are known as oral papillae, tooth papille, and teeth,
according to the position they occupy on the jaw. The oral
papille are toothlike projections along the edges of the
jaws, while the tooth papillz, when present, are similar structures
at the point of the jaw, and the teeth are five series of plates
which project from the mouth opening toward the interior of
the body. The oral papillae and teeth are well shown on Plate
XIII, while Fig. 9 represents in a diagrammatic way the rela-
tions of the same plates. The number and arrangement of these
processes are characteristic of each of the different species.

The jaws are provided with a musculature which permits
them to be opened widely (Plate XIII and Fig. 9) or closed
tightly. In the specimen shown on Plate XIV two adjacent jaws
are thus closed, while the remaining angles of the mouth have
remained open. In most species the jaws, teeth, and oral papille
are not so much used in crushing the food as in separating out
and swallowing the smaller or softer particles.

A large plate at the base of each jaw is termed the oral shield,
while the pair of smaller plates on the face of the jaw, and
beside or internal to the oral shield, are the adoral plates (Plate
XIII and Fig. 9).

On the aboral surface there is great variation in the number
and size of the plates, but one pair — the radial shields —lie at
the base of each arm. In some species, as Amphipholis squamata,
these radial shields are very large and conspicuous (Plate XVII),
70 CONNECTICUT GEOL. AND NAT. HIST. suRVEY.. [Bull.

while in other species they are more or less completely covered
by the more superficial scales of the disk (Plates XIII and XIV).

wiyZ a

 

Fic. 9. Oral surface of disk and basés of arms of
Ophiopholis aculeata; a, adoral plate; d, disk, with
small, blunt spines covering the plates; e, tentacle
scale; g, genital slit; m, madreporic plate (modified
oral shield); 0, oral shield; p, oral papille; s, arm
spine; ¢, tooth; u«, under arm plate.

Arm plates.— The arms are covered on all sides by a com-
plicated system of thin plates and spines. The form, number,
‘and arrangement of these parts are used in the classification of
the group, so that one must examine them closely in order to
determine the name of any one of our native species. A single
row of plates, the upper arm plates, usually lies along the aboral
surface of each arm; and a similar row, the under arm plates,
often with plates of different size, occupies a similar position on
the oral surface (Fig. 9). Beside these upper and under arm
plates, and occupying more or less of the lateral surfaces of the
arm, often occur one or more series of smaller plates, and these
 

 

 

PLATE X1V, Skeleton of Ophiuran, Ophzura brevispina, (Five times natural size.)
No. 19.] ECHINODERMS OF CONNECTICUT. 71

commonly bear conspicuous spines, termed arm spines. The
number of spines is nearly constant on the corresponding
parts of the arms in all individuals of the same species, and
‘moreover each species presents its own peculiarities in the size,
position, and arrangement of these structures, as is shown on
Plates XIII and XIV. Hence their importance in the diagnosis
of the species.

Tube-feet.—The tube-feet are small and inconspicuous, and,
as they have no sucking disks nor ampulle, they are of compar-
atively little importance in the locomotion of the animal. They
function largely as sense organs, and are therefore often called
tentacles. They are also of service in respiration by the ex-
change of gases which takes place between their fluid contents
and the external sea water, and in some cases they aid in pass-
ing food particles to the mouth. In certain species the greater
portion of the food consists of small organisms which are secured
by the tentacles as the slender arms are swept back and forth on
the surface of the sand or mud. The food secured is passed
along from one tentacle to the next until, on reaching the
proximal tentacles, it is pushed between the jaws and into the
mouth.

The tentacles protrude between the lateral plates of the arm,
and are protected by delicate scales, called the tentacle scales
(Plates XIII and XIV, and Fig. 9).

Internal structure of Arms.— The arm of the ophiuran is
morphologically equivalent to that of the starfish, but the struc-
tures have undergone great modification. Instead of a broad

 

 

EXPLANATION OF Pirate XIV. Skeleton of Ophiuran, Ophiura brevispina.
(Five times natural size.)

Photographs of dried specimens, showing aboral and oral surfaces
of disk and bases of rays. In the upper figure the granules covering the
surface of the disk have been removed on the side toward the top of the
page to show the underlying radial shields and other plates.

The lower figure shows the plates around the mouth and on the
under side of the rays. Of the five large oral shields the one on the
lower right-hand side is somewhat larger than the others, and is the
madreporic plate. The adoral plates Jie close beside the oral shields.
The figure shows the teeth at the apex of the jaws, and the seven oral
papilla on each side of each jaw. The left side of the mouth shows
the position of the jaws when closed. The two pairs of large openings
near the base of each arm are the genital slits. On the arms the upper
and under. arm plates, the tentacle scales, and the closely appressed arm
spines are shown. 1
72 CONNECTICUT GEOL, AND NAT. HIST. SURVEY. [ Bull.

central cavity occupied by the digestive and reproductive organs,
the body cavity in the arm of the ophiuran is represented only
by a narrow canal (Fig. 10). Each arm is made up of a great
number of similar segments. The bulk of the arm consists of
a series of solid, cylindrical disks, called vertebre, which are
arranged end to end in a single row, and taper gradually to the
tip of the arm.

 

 

 

 

 

 

Fic. 10. Diagram of transverse section of
arm of an ophiuran. C, branch of celom; L,
lateral arm plate; M, muscular attachment of
vertebra; N, radial nerve; S, arm spines; T,
tentacle; TS, tentacle scales; U, upper arm
plate; UN, under arm plate; V, vertebra; W,
radial canal of water-vascular system. (Modified
from MacBride.)

Each vertebra, in all our native species, articulates with its
neighbor by a ball-and-socket joint, the concavity on the proximal
side interlocking with a corresponding projection on the distal
side of its neighbor.

The vertebrze are joined to each other by four strong muscles
(Fig. 10), attached symmetrically to their faces. The contrac-
tion of the two upper muscles of a series of segments bends the
arm upward; a similar contraction of the lateral or lower pair
bends the arm sidewise or towards the oral surface as the case
may be. By suitable combinations of such muscular contractions
the arms can be moved rapidly and bent about in all possible
directions, with the one exception that they are so articulated
that they cannot be coiled in a spiral above the disk.

On the aboral side of each vertebra (Fig. 10) is a shallow
groove which contains the slender extension of the body cavity,
No. 19.] ECHINODERMS OF CONNECTICUT. 73

mentioned above, although no part of the digestive or other sys-
tems extend into it.

A similar groove on the oral side of the vertebre contains
the radial canal of the water-vascular system, which is connected
with each of the tentacles, as with the tube-feet of the starfish.
Beneath the radial canal is the radial nerve cord and the peri-
hzmal canal comparable to those of the starfish.

The upper arm plates cover the extension of the body cavity,
just as the under arm plates cover the organs beneath the ver-
tebre (Fig. 10).

Viscera.— The visceral anatomy of the ophiuran is not essen-
tially different from that of the starfish, except that the digestive
and reproductive organs do not extend at all into the rays. The
simple digestive organs, mouth and saccular stomach, have been
described above. The water-vascular system consists, as in the
starfish, of a circumoral vessel and five radial canals, connected
with the tentacles of the arms. The madreporic canal is con-
nected with the exterior by one or more minute pores situated
on one of the oral shields.

The nerve ring and its branches and the perihemal vessels
have much the same situation as in the starfish, although the
nerves are more highly modified by the segregation of the nerve
cells into more definite centers, or ganglia.

HABITS

The ophiurans are usually nocturnal in habit, some species
hiding away in protected places during the daytime, others
remaining buried in the mud. When disturbed they hastily swim
or creep away. In case the irritation has been too severe some
species spasmodically throw off and leave behind one or more
of their arms. This causes them only a temporary inconven-
ience, however, for such mutilated individuals rapidly regenerate
the missing parts.

Ambulacral grooves, so well developed on the oral surface
of the rays in the starfish, are lacking, and the tube-feet are so
little developed that the movements of the animal are controlled
by the flexible, muscular arms. They provide, however, a much
more rapid means of locomotion than is afforded by the tube-feet
of starfishes. The ophiuran can move rapidly among seaweeds,
74 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [ Bull.

pebbles, or other objects by the serpentine movements of these
arms, and can also swim free in the water by moving a pair of
arms much as we would move our own arms in swimming.
When placed upon its aboral surface the animal can quickly
recover its normal position.

In ordinary locomotion one or more of the arms are clasped
about an object and the rest of the body drawn forward to that
position, when the same or adjacent arms reach out again to an
advanced position and the animal moves rapidly forward. The
more posterior of the arms help push the body along at the
same time that those in front are pulling.

There is no definite orientation of the body, and any of the
arms may go in front, so that when the animal desires to change
its direction it does not turn the body, but merely advances an
arm which was previously in the rear. It may thus go in any
direction without turning the body.

When spines are well developed along the sides of the arm
they aid materially in furnishing a means of attachment to any
desired object. The rudimentary tube-feet, or tentacles, also aid
the arm in keeping its hold, although they are not provided with
the sucking disks present in those of the starfish and sea-urchin.

The motion of the arms is controlled by the circumoral nerve
ring. When this ring is cut, the movements of the adjacent
arms are impaired; and, when it is cut between each pair of
adjacent arms, codrdinated movements are entirely destroyed.

The habits and response to stimuli of these animals have been
the subject of much study in recent years. Cowles has recently
shown* that the tube-feet are capable of selecting food materials
with much precision and passing them from one tube-foot to
another until the mouth is reached. Even when removed from
the body the arm still reacts to food, and nutritive particles are
carried from tip to base of the severed arm, while inorganic
objects are seized and quickly dropped.

The ophiuran reacts positively to solid vertical walls, and
the efféct of such a stimulus is retained for some time, for when
an animal is removed a short distance from its hiding place it
moves in the direction of the same spot without error. This

’

* Stimuli Produced by Light and by Contact with Solid Walls as Factors in the
Behavior of Ophiuroids. Journ. of Exp. Zool., vol. ix, 1910.

 
No. 19.] ECHINODERMS OF CONNECTICUT. 75

so-called memory of past stimulation is lost under the influence
of a much stronger stimulus, such as bright light, from which
the animal retreats rapidly.

The behavior of the ophiuran when subjected to a great
variety of artificial conditions has been studied by Glaser.*
The animal’s ability to solve to its advantage many of the prob-
lems set for it, such as removing rubber bands from its arms,
for example, illustrates a high degree of nervous codrdination.

Regeneration.— The rays of all our species are fragile, and
are so likely to be broken off in handling, that in some species it
is difficult to kill and preserve a specimen without mutilation.
Some of the species voluntarily throw off one or more rays at a
point close to the disk if the animal is even slightly irritated
by rough handling or by being placed in a fluid not to its liking.
Other forms when disturbed break off the arms piece by piece
until nothing of the animal remains except the disk.

When one or more rays are accidentally or voluntarily broken
off in a state of nature, the wound quickly heals and new rays
grow out from the disk in place of those destroyed, as in the
case of the starfish,

If a ray is broken at some distance from the disk the end is
restored to the normal length. Individuals are often found, as
illustrated on Plate XII, which show such rays in process of
regeneration. If the disk is cut in two each part is capable of
regenerating a complete animal.

Certain species, such as Amphioplus abditus, have the remark-
able habit of throwing off the disk when strongly stimulated,
leaving only the mouth frame attached to the arms. Under
favorable conditions the missing parts can be regenerated. In
Amphipholis squamata, in which the young develop in the genital
bursz, this process of throwing off the disk is said to be the
normal method by which the young are discharged.

FOOD

Because of their secluded and nocturnal habits it is difficult
to determine the exact nature of the food on which the ophiurans
subsist. The animals are seldom seen to take any food whatever

* Movement and Problem Solving in Ophiura. Journ. of Exp. Zool., vol. iv, 1907.
76 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.

when kept in an aquarium, but an examination of the contents
of their stomachs often reveals fragments of the indigestible
parts of small crustaceans and other animals. Since it seems
doubtful if the ophiuran would be able to capture these animals
alive, it is believed that it acts mainly as a scavenger, taking
into the large saccular stomach all sorts of dead animal matter
and digesting out the substances capable of assimilation. Those
parts which cannot be digested are thrown out of the mouth
opening.

Probably the greater part of the food of many species con-
sists of the superficial layer of organic matter which covers the
rocks and floor of the sea in all situations not accessible to
waves and currents. The diatoms and other minute organisms
contained therein are passed toward the mouth by the tube-feet
of the arms.

Some species crawl about on the sea-bottom sweeping the
arms back and forth in search of food materials. Other species,
such as Amphioplus abdditus, lie for a time buried in the mud
with one or more of the extremely slender arms protruding
above the surface of the mud. The tube-feet (tentacles) of
these arms select the food particles within reach and pass them
to the mouth.

REPRODUCTION

The reproductive organs consist ordinarily of five pairs of
genital glands, situated on the walls of five sacs called the genital
bursz, which open to the exterior of the body by five or ten pairs
of large slits situated on the oral surface of the disk close beside
the bases of the rays. These openings are called the genital slits,
and are usually quite conspicuous (Fig. 9 and Plate XIV).

The sexes are usually separate, all the glands in one individ-
ual producing eggs and in another spermatozoa. In the little
Amphipholis squamata, however, one of the glands of each
genital bursa produces eggs while the other forms sperm cells.

The sexual products when ripe break out of the sexual glands
into the genital bursz and are usually discharged directly through
the genital slits, although in the above-named hermaphrodite
species the eggs are fertilized and develop within the genital
burse.
No. 19.] ECHINODERMS OF CONNECTICUT. 77

Owing to the nocturnal habits of the animals the eggs of at
least some of the species are discharged in the evening; that is,
between sunset and midnight. They are set free in the water
and are there fertilized by spermatozoa from another individual.
After fertilization the egg develops into a free-swimming ciliated
larva, which by a complicated metamorphosis gives rise to the
young ophiuran as described in the following chapter.

The genital bursz are thin-walled sacs; and, as the sea water
contained in them has free access to the exterior through the
genital slits, and can be continually changed by the contraction
of the disk, the bursz serve as respiratory organs in addition to
their primary function of discharging the genital products. The
minuté tentacles of the arms also aid in respiration.

DEVELOPMENT

In most species of ophiurans the genital products are simply
discharged into the sea water, and abandoned to their fate. In
the little Amphipholis squamata, however, the eggs are retained
within the body of the parent until the embryonic development
is completed and the little ophiuran has reached the form of
the adult. Moreover, in this case, a nourishing exudation is said
to be poured out upon the eggs, which supplements the store of
food contained in the yolk.

This species is likewise hermaphrodite, both ovary and sperm-
ary being attached to each of the genital burse. After the young
have reached the adult form, the whole disk of the parent, with
the exception of the mouth frame, may sometimes be thrown
off to allow the young to escape, and then be regenerated. The
breeding habits and development of this species have been studied
by Fewkes* and others.

In the majority of ophiurans, the sexes are separate, the eggs
being thrown out into the water, and fertilization takes place
whenever suitable sperm cells are in the vicinity.

The eggs segment by a regular cleavage, as in the starfish
and sea-urchin. As in these two groups, the embryos quickly
develop into free-swimming larve, which in this class are called
plutei, and which often feed for several weeks at the surface of

* Bull. Museum Comparative Zoology, vol. xiii, 1887.
78 CONNECTICUT GEOL. AND NAT. HIST. SURVEY, [Bull.

the sea. As shown in Fig. 11, the plutei in no way resemble the
adult, but are somewhat pyramidal in form, and often have

 

Fic. 11. Ophiopholis aculeata. Free-swimming larva, with long,
ciliated arms. (Modified from Fewkes.)

 

Fic. 12. Ophiura brevispina. Free-swimming larva preparatory
to transformation to the adult form. (After. Grave.)
[
F
FS
'
i
i
:
t
i
\

PLATE XV. Ophiura brevispina, (Twice natural size.)
Oral and aboral surfaces of dried specimens. ‘The fragile tips of several of the

rays have been broken off, and the lower figure shows one ray in process of regen-
eration,

 
No. 19.] ECHINODERMS OF CONNECTICUT. 79

extremely long, ciliated arms. Fig. 12 shows the larva of another
species, in which there are four bands of cilia in place of the long
arms. The metamorphosis is accomplished in a manner similar
to that described for the starfish.

KEY TO SPECIES

The ophiurans of the world are commonly divided into three
orders, distinguished by the character of the vertebra. Only one
of these orders, the Zygophiure, with interlocking vertebre, is
represented in Long Island Sound.

1. Spines on sides of arms short, and rather closely pressed
against the arms................ Ophiura brevispina

Spines projecting from sides of arms at a marked angle. .2

2. Large median plates on upper side of arms surrounded by a
series of small plates; 5 or 6 spines on each side of each

jomt, Of AlN, se. rccwe ses enees 3 Ophiopholis aculeata
Median plates on upper side of arms directly in contact;
that is, not surrounded by small plates............... 3

3. With 3 tooth-like projections (oral papille) along each edge
of each jaw; length of arms less than 10 times the
diameter of disk; radial shields in close contact
Amphipholis squamata

With 4 or 5§ oral papillae on each edge of each jaw; length

of arms more than 10 times the diameter of disk; radial

shields separated ............ 4 WEEE ERS Reh 4
4. (OFal papille Ay .oi ince e4 cag eee Amphioplus abditus
Oral papilla 533 .seusanes ee ececeen Amphioplus macilentus

Ophiura brevispina Say, var. olivacea
Green Ophiuran
Plate I, fig. 5; Plates XIV, XV.

This species, which was described by Say in 1825, is known
in the earlier writings of Lyman and Verrill under the name of
Ophiura olivacea. It has been found in shallow water at num-
erous localities along the Atlantic coast from Cape Cod to Brazil,
and at Bermuda. It is sometimes found, however, at a depth
of over a hundred fathoms, especially in the warmer regions.
80 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.

The form occurring north of Florida is now usually consid-
ered a distinct variety, olivacea.

This ophiuran occurs at numerous localities in Long Island
Sound, living in water but a few feet deep at low tide, and is
partial to protected situations and tide pools. It is often abun-
dant on sandy shores among the roots of eelgrass. In such
places the bottom is often covered with a mass of dead grasses
and alge, and forms the home of numerous other small animals,
such as worms, mollusks, and crustaceans. Here the ophiuran
hides during the daytime and is seldom seen unless disturbed.
The snake-like movements of the arms may then attract atten-
tion, but the color of the animal when resting agrees most
closely with that of the surrounding objects, and the appearance
of the arms is quite similar to that of fragments of the stems
of the eelgrass.

The color is commonly greenish or brownish but is some-
times nearly black. Olive-green individuals are perhaps the
most common. The disk is often mottled and the arms banded
with light and darker shades, but the colors are always dull and
inconspicuous.

The disk is usually Io to 15 mm. in diameter, and the arms
40 to 60 mm. in length. The arms are rounded and moderately
slender, as indicated on Plates I and XV. Each segment of the
arm has seven or eight short spines on each side, and these lie
closely appressed to the arm, so that they are quite inconspicuous,
as shown on Plates XIV and XV.

A most interesting account of the habits and development of
this species has been published by Grave.*

Ophiopholis aculeata (Linnzus)

Daisy Brittle Star
Plates XII, XIII, XVI.

This is without question the most beautiful and most con-
spicuous of all our native ophiurans, but unfortunately it is but
rarely found in Connecticut waters, and there occurs only in the
deeper areas toward the eastern portion of Long Island Sound.
North of Cape Cod the species is very abundant and is there

 

*Ophiura brevispina. Mem. Nat. Acad. Sciences, vol. viii, 1899-
 

 

 

 

PLATE XVI. Daisy Brittle-star, OpAcophols aculeata. (One and one-half times
natural size.)

 
PLATE XVII. Amphipholis sguamata. (Fig. 1, one and one-half times natural
size. Figs. 2 and 3, natural size. Figs. 4 and 5, ten times natural size.)

 
No. 19.] ECHINODERMS OF CONNECTICUT. 81

commonly known as the “daisy brittle star.” It extends
northward to the Arctic Ocean, and on the European coast
reaches southward as far as the English Channel. It is larger
than any other of our species, the disk often being 15 to 20 mm.
in diameter, and each of the arms 50 to 80 mm. in length.

The colors are exceedingly variable, not only in hue but also
in the arrangement of the patterns. There are all shades of red,
purple, brown, yellow, and green. The disk is spotted and
blotched in some regular pattern arranged either radially or con-
centrically or both, while the arms are either banded or striped
lengthwise (Plate XII.) The bright colors are limited to the
aboral surface, the under side of disk and arms being commonly
gray or yellowish, except that the dark bands on the arms often
extend more or less completely over the oral surface. Of a
hundred individuals taken at random scarcely two will agree
closely in both shade and arrangement of markings, so that the
individuality of the representatives of this species of ophiuran
is more conspicuous than in almost any other invertebrate.

Amphipholis squamata (Delle Chiaje)

Plate XVII.

This is the smallest species of ophiuran recorded on our
coast, and it is also the most abundant and the most widely dis-
tributed. On the Atlantic coast of America it occurs from the
Arctic Ocean to the coast of New Jersey, and it is also found on
the northern coasts of Europe and in the Mediterranean Sea.
In America the species is often referred to under the name of
Amphipholis elegans or Amphiura elegans, and in Europe is
sometimes called Amphiura squamata.

 

 

EXPLANATION oF PLateE XVII. Amphipholis squamata.

Fig. 1. Four specimens showing both oral and aboral surfaces. The
tips of several of the very fragile rays have been broken off.
One and one-half times natural size.

Fig. 2. Aboral surface. Natural size.

Fig. 3. Oral surface. Natural size.

Fig. 4. Oral surface. Enlarged ten times. : :

Fig. 5. Aboral surface, showing the smooth scale-like plates which cover
the disk. The narrow radial shields are in close contact with
each other. Each segment of the arms has three arm spines
on each side. Enlarged ten times. : oan:

(Figs 2 and 3 from photographs loaned by the U. S. Fish Commission,

with permission of Dr. H. L. Clark.)

6
82 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.

In Long Island Sound this ophiuran occurs on the eelgrass
in New Haven harbor, and has been collected at several other
localities in shallow water, hiding in dead mollusk shells and in
the interstices of stones.

The diameter of the disk is 3 to 5 mm., and the length of
each of the five slender arms is from Io to 20 mm.

The color is gray or pale brownish, often with numerous
lighter or whitish spots. The oral surface is gray with a yellow-
ish tinge, usually with a whitish spot at the base of each arm.
In very young specimens the disk is orange.

The disk is flattened and nearly circular (Plate XVII), and
is covered with small scales. The arms have three spines on
each side of each segment, and these stand out at nearly right
angles to the axis of the arm, as shown in the figure.

A detailed description of the arrangement of scales on disk
and arms is to be found in Clark’s Report on the Echinoderms
of the Woods Hole region.*

In this species the eggs mature in midsummer and are retained
in the genital burse after fertilization. They there develop into
young ophiurans, which are then discharged from the body as
tiny brittle stars, of form and structure like the parent. They
do not undergo the metamorphosis characteristic of the other
species, for none of our other species is known to be viviparous.

Amphioplus abditus Verrill
Plate XVIII; Plate XIX, fig. 1.

This locally distributed species was for many years known
only from Long Island Sound. Quite recently, however, a single
specimen has been recorded from the harbor at Woods Hole,
Massachusetts,t and one specimen was collected by the writer
some years ago at the same locality.

- The animal lives buried in the soft mud, and when exposed
quickly buries itself again. Verrillt states that it naturally lies
with one or more of the very slender arms projecting above
‘the surface of the mud. “On this account it is seldom dredged

* Bulletin U, S. Fish Commission for 1902, p. 560.

+H. L. Clark, Science, vol. xxvii, p. 147, 1908.
t Invertebrate Animals of Vineyard Sound, p. 139.
PLATE;/XVIII. Amphioplus abditus. (Slightly enlarged.)
Two individuals, showing both oral and aboral surfaces of disk, and the ex-
tremely slender rays.

 
No. 19.] ECHINODERMS OF CONNECTICUT. 83

entire; the projecting arms are usually cut off by the dredge, and
the animal escapes; and as it has the power of restoring lost
arms, this is only a temporary inconvenience. The same thing
probably happens when a voracious fish seizes one of the arms.”

The specimens from Woods Hole were collected at extreme
low-water mark. In Long Island Sound the species has been
dredged off New Haven and at Thimble Islands at depths of
from three to eight fathoms, and many specimens have been
collected in soft mud, near low-water mark, at Noank, Connecti-
cut, and others at Peconic Bay, Long Island.

The disk of mature individuals measures from 6 to 11 mm. in
diameter. The arms are very slender and extremely flexible.
They are usually from twelve to sixteen times as long as the
diameter of the disk, and sometimes measure as much as 180 mm.
in length.

In addition to the extremely long and slender arms (Plate
XVIII, Plate XIX, fig. 1), the species may be distinguished by
other anatomical peculiarities. Careful examination of the jaws
will show the presence of four tooth-like processes, oral papilla,
on each edge. On the sides of each segment of the arm is a
series of three projecting spines, of which the middle one is
stouter, flatter, and less pointed than the other two.

On the aboral side of the disk at the base of each arm is a
pair of narrow plates, called the radial shields. In the present
species these are narrow, curved, and parallel or only slightly
divergent, and not closely in contact. They are often partly
covered by the encroachment of the small scales which cover the
disk. The scales of the disk are without granulations or spines.

The color of the living animal varies considerably in different
specimens. Some are brown on the aboral surface of the disk,
with a central area of dark brown bordered by pale gray. A
radiating band of dark brown likewise bordered by gray extends
outward to each interradial margin. The radial shields are yel-
lowish brown, while the narrow space between them is blue.
There are additional symmetrically placed brown spots arranged
in series on the disk. The arms are brown or dull greenish,
often with lighter bands. The specimen from Woods Hole
studied by Clark was uniformly gray.
84 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [ Bull.

The animals have remarkable powers of regeneration, for
they have the habit of throwing off the disk when violently dis-
turbed, leaving only the mouth frame and adhering organs at-
tached to the arms. Under favorable conditions they are able
to regenerate the missing disk, and specimens have been collected
in which such regeneration was actually in progress.

Full details of the anatomical peculiarities are given in Ver-
rill’s original description of the species.*

The species is also fully described in Verrill and Smith’s
Invertebrate Animals of Vineyard Sound, page 426, although the
description there given has been revised in certain details in a
later paper by Verrill.t

Amphioplus macilentus Verrill
Plate XIX, fig. 2.

This species is closely related to the preceding, but is dis-
tinguished by having five oral papillz in each row, and the spines
at the sides of the arms are all slender.

Although this species has not yet been recorded from Long
Island Sound, it has been collected at various localities so near
the eastern entrance to the Sound as to render it highly probable
that further investigation will reveal its presence in Connecticut
waters. It has been dredged by the United States Fish Com-
mission in muddy localities at numerous stations off the south-
eastern coast of New England, and in certain places occurs in
large numbers as far south as Cape Hatteras.

Full details of the anatomical peculiarities are given in Ver-
rill’s original description of the species.t

The individuals belonging to this species are small, with
very long and slender arms (Plate XIX, fig. 2). The disk is

* Am. Journ, Sci., 3rd series, vol. ii, p. 132, 1871,
¥ North American Ophiuroidea. Trans. Conn. Acad., vol. x, p. 314.
tAm, Journ. Sci., 3rd series, vol. xxiii, p. 142, 1882.

EXPLANATION OF PLATE XIX.

Fig. 1. Amphioplus abditus. Oral surface of disk and portions of rays.
One of the extremely slender rays is in process of regenera-
: tion. Three times natural size.
Fig. 2. Amphioplus macilentus. Oral and aboral surfaces, showing the
extreme slenderness of the rays. Twice natural size.
Missing Page
 

 

 

 

 

 

 

PLATE XX. Purple Sea-urchin, Arbacra punctulata. (Natural
size.)

 
No. 19.] ECHINODERMS OF CONNECTICUT. 85

nearly circular in outline in the living animal, but often becomes
pentagonal when preserved in alcohol or dried. The aboral sur-
face of the disk is covered with numerous, small, naked, imbri-
cated scales, forming a rather distinct rosette at the center. The
radial shields are long and narrow, with their outer ends in con-
tact, and their inner ends separated by a narrow wedge of small
scales.. The oral surface is covered with more minute scales
than those of the aboral surface. The oral shields are shield-
shaped, rather longer than wide.

The five oral papillae are unequal in size, but all are obtusely
rounded. The inner one is the largest and stoutest, while the
next is the smallest and most acute; the next two are flattened,
while the outermost is small and rounded.

The under arm plates are shield-shaped and longer than
broad. Near the base of the arms they are in contact, but farther
out they are separated by the side arm plates. Tentacle scales
two. Arm spines three, nearly equal, about as long as the joints.

Color light gray. Diameter of disk about 4 mm. Length
of the extremely slender arms about 60 mm.

CLASS III. ECHINOIDEA

This class includes the animals popularly known as sea-
urchins, sand-dollars, cake-urchins, disk-urchins, sea-cakes, and
sand-cakes. In the sea-urchins the body is nearly hemispherical,
while the others are flattened and discoid. Spines thickly cover
the body on all sides, except sometimes at the poles. In one of
our species (Mellita pentapora) the disk is pierced by five oval
perforations.

STRUCTURE

If the purple sea-urchin (Arbacia punctulata) be taken as
an example of this group, the body is seen to be enclosed in a

 

 

EXPLANATION oF Pirate XX. Purple Sea-urchin, Arbacia punctulata.
(Natural size.)

The larger specimen (lower figure) shows the oral surface, with the
five sharp white teeth in the center; while the smaller specimen (upper
figure) shows the aboral surface, in the center of which is the periproct,
surrounded by a broad area free from spines. (After Clark.)
86 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. {Bull.

firm, hemispherical shell made up of 20 meridional rows of closely
fitting plates, and with a wide circular aperture at one pole
(Plate XXV). Ina living specimen of this same species (Plate
XX), the shell, or test, is so thickly covered with long stiff spines
as to obscure its surface completely except at the poles.

At one pole of the body may be seen the five sharp, calcare-
ous teeth surrounding the mouth. This is therefore the oral, or
actinal pole of the body; the opposite pole being aboral, or
abactinal. Around the mouth is a broad area devoid of large
spines, called the peristone. It consists of a strong membra-
nous wall with an abundant musculature, enabling the mouth to
be opened and closed. The peristome is provided with numerous
slender pedicellarie, which differ from those of the starfish in
having three blades, which form the angles of a triangle. Sim-
ilar pedicellarize are scattered over the body. The circular lip
surrounding the teeth can close the mouth very tightly (Plate
XX). :

At the aboral pole there is likewise a considerable area (Plate
XX) devoid of spines, in the center of which is a cluster of
movable plates (Fig. 13) constituting the periproct. The intes-
tine opens in the center of the periproct. In the species under
consideration the periproct consists of four triangular plates,
while in the other native species of sea-urchin (Strongylocentro-
tus drébachiensis) there are many minute plates (Plate XXI).
The spines which cover the surface of the test vary somewhat
in shape, but all are cylindrical, solid, and longitudinally fluted.
These spines not only constitute a very formidable defensive cov-
ering, but are used in locomotion. Some of the spines nearest
the aboral pole are sharply pointed, while others are blunt; below
the equator of the test the tips of the long spines are somewhat
flattened and rounded, while those nearest the peristome are
short, and spatula-like, with flattened, rounded tips (Plate XX).

The base of each spine has a rounded socket which fits closely
against a corresponding hemispherical tubercle on one of the plates
of the test, allowing a great range of movement. Closely fitting
this ball-and-socket joint is a wreath of muscular fibers attached
both to test and spine. These muscles are able to move the spine
in all directions. Beneath these “moving ” muscles is a wreath
of specialized muscle fibers whose function is, when stimulated,

t
Missing Page
No. 19.] ECHINODERMS OF CONNECTICUT. 87

to set the spine stiffly in one direction. As long as the action
of this muscle lasts the spine can only be moved by tearing the
muscle.

The test denuded of spines (Plate XXV) shows clearly the
regularity with which the spines are arranged, each tubercle indi-
cating the position of a spine. In Strongylocentrotus there are
numerous smaller secondary spines between the larger ones, as
shown by the smaller tubercles (Plate XXI). In this genus
there are several times as many spines as in Arbacia.

Both the tube-feet and the spines assist in locomotion, as
described below.

An examination of a living specimen shows five pairs of
meridional groups of very slender tube-feet, which are capable of
expanding to great length. The extremity of each tube-foot on
the oral surface has a sucker-like expansion, kept open by a per-
forated calcareous plate. The position of the tube-feet is indi-
cated in the denuded test (Plate XXV) by the ten series of plates
with minute perforations. These ten series of openings corre-
spond with the groups of tube-feet seen in the living animal, each
pair of openings representing the position of a single tube-foot.

The series of ten rows of plates which bear the tube-feet con-
stitute the five ambulacral, or radial areas, there being two
rows of plates to each. Between the ambulacral areas are five
interambulacral, or interradial, areas of about equal extent.
Each of these five areas likewise consists of two meridional rows
of plates (Fig. 13).

The ambulacral areas may thus be seen to represent the oral
surfaces of the arms of the starfish, bent upward in a semicircle,
while the interambulacral areas correspond to the sides of the

 

 

EXPLANATION OF PLaTE XXI. Skeleton of Sea-urchin, Strongylocentrotus
drébachiensis. (Natural size.)

Figs. 1 to 3. Aboral, lateral, and oral surfaces with spines removed,
showing the regularly arranged rows of larger and smaller tubercles
which in life bear the primary and secondary spines respectively. Scat-
tered among the larger tubercles are numerous minute tubercles which
bear the miliary spines. The oblique rows of minute dots arranged in
pairs represent the pores for the tube-feet, and indicate the position of
the five double rows of plates of the ambulacral areas. Of about equal
extent are the five interambulacral areas. In Fig. 1 the centrally placed
periproct, consisting of many minute plates, is surrounded by a circle of
larger ocular and genital plates. In Fig. 3 the peristome and jaws have
been removed.
88 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. {Bull

arms, firmly fitted together. Thus the entire aboral surface of
both disk and arms of the starfish can be represented in the
sea-urchin only by the few plates of the periproct.

Each ambulacral area ends near the periproct in a single
plate called the ocular plate (Fig. 13), perforated by a pair of
minute openings from which a tentacle protrudes, as at the end
of the arm of the starfish. The interambulacral areas likewise
terminate in single large plates called the genital plates, because
they bear the five openings of the genital glands (Plate XXV).
One of these genital plates is larger than the others, and is per-
forated by numerous minute pores which lead to the water-
vascular system. This plate is therefore termed the madreporic

plate (Fig. 13).

 

Fic. 13. Arbacia punctulata. Out-
line of plates of aboral surface,
showing the four plates of the peri-
proct, surrounded by the five ocular
and five genital plates at the ends
of the ambulacral (R) and _inter-
ambulacral (J) zones, respectively ; the
genital plate marked M is the madre-
poric plate; T, tubercles for attach-
— of spines; P, pores for the tube-
eet.

At the margin of the peristome are five pairs of much
branched processes, having a respiratory function, and termed the
dermal branchiz, or gills.

Just inside the test at the border of the peristome, and resting
upon the bases of the ambulacral areas, are five pairs of calcareous
 

PLATE XXII. Anatomy of Sea-urchin.
No. 19.] ECHINODERMS OF CONNECTICUT. 89

pillars, the auricles, to which are attached the powerful muscles
for protruding and retracting the jaws. In Strongylocentrotus
the pillars of each pair are connected by a bridge.

Internal Anatomy.— If the test is cut through at the equa-
torial region, and the two portions laid side by side without
injuring the alimentary canal, the internal organs of the sea-
urchin are easily studied. The more prominent organs to be
seen in such a dissection are shown on Plate XXII.

Digestive System.— In the sea-urchin, the mouth, situated
in the center of the oral surface, is provided with five sharp cal-
careous teeth which meet closely in the axis of the body and
close the mouth completely. These teeth are set in jaws which
are moved by a complicated set of muscles attached to a cal-
careous frame-work; this, with the attached teeth, is often called
the lantern. When the jaws are separated the mouth presents a
wide opening leading into the esophagus. The latter is short,
and at its end divides into two branches, of which one is coiled
irregularly for some distance and opens into the wide, saccular
stomach, while the other forms the siphon (Plate XXII).

The stomach is broad and flat; its walls are irregularly con-
stricted to form numerous sac-like pouches which greatly increase
the surface area. It makes a nearly complete circle at the equator
of the body and then bends sharply upward and passes into the
narrower intestine. The intestine is also flat, and at its beginning
bends directly backwards and encircles the body. Its course lies
parallel with the stomach but it leads in the opposite direction.

 

 

EXPLANATION oF PLATE XXII. Anatomy of Sea-urchin. Arbacia
punctulata, showing the arrangement of the internal organs. The test
hds been cut horizontally and the two parts laid side by side without
cutting the alimentary canal; the upper circle representing the aboral
portion of the test and the lower circle the oral part. At the center of
the lower section the mouth opens into the esophagus (e) from which
the spihon (siph) and stomach (st) branch out. The intestine (int) in
the upper section lies parallel with the stomach in its natural position,
but its course is in the opposite direction. The rectum (r) opens through
the anus at the center of the upper section. The five sexual glands (s. g)
open by narrow ducts on the aboral surface near the anus. The five teeth
(t) lie at the five angles of the mouth. The ring canal (r.c) with the
five interradial pouches (7p) are shown. Beside the esophagus lies the
delicate madreporic canal with its dorsal ampulla (s. c’) although the con-
nection of the latter with the aboral surface has necessarily been torn
away. The rows of ampulle (amp) and tube-feet (#.f) connected with
the radial canals are shown in both sections.
90 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. { Bull.

After making a nearly complete circle, the intestine passes grad-
ually into the rectum, which bends obliquely upward and opens
to the exterior in the center of the aboral surface.

The siphon makes a short cut between the esophagus and the
posterior end of the stomach. It consists of a narrow tube im-
bedded in the inner wall of the stomach, and is lined throughout
with a strongly ciliated epithelium, which presumably draws a
stream of water from the esophagus to the intestine. This water
doubtless aids in respiration, and may also serve to wash indi-
gestible food materials out of the alimentary canal.

The food of the sea-urchin consists of seaweeds and various
small animals. Some species devour such dead animal matter as
can be obtained, individuals sometimes collecting in numbers on
the body of a dead fish. The organic matter on the surface of
the sea bottom is also used for food, while certain species are
said to capture and devour large crustaceans. The sharp chisel-
like teeth would seem to fit the creature for devouring almost any
kind of plant or animal matter which by its slow method of loco-
motion it is able to secure.

Water-vascular System. From the madreporic plate, the
madreporic canal leads directly down to the circular vessel, which
is situated immediately above the jaws and surrounds the base
of the esophagus. Connected with the circular vessel are five
interradial pouches, or Polian vesicles (Plate XXII).

Five radial vessels, similar to those of the starfish, leave the
circular vessel, pass to the borders of the peristome and thence
along the inside of the test directly beneath the ambulacral areas,
and end in the terminal tentacle of the ocular plate. The radial
vessels supply the tube-feet as in the starfish, each tube-foot con-
necting with an ampulla inside the wall of the test (Plate XXII).
Two perforations of the plates of the test are provided for each
tube-foot, so that the contained fluid may enter the foot by one
canal and return to the ampulla by the other. Internal cilia keep
up this circulation of fluid, and by this means the fluid in the
tube-feet is continually changing. An exchange of gases can
take place between the fluid contained in the tube-feet and the
sea water, and a supplementary respiration is accomplished
thereby. In Arbacia only the tube-feet of the lower part of the
body are provided with suckers and used for locomotion, those
No. 19.] ECHINODERMS OF CONNECTICUT. gI

of the upper part being specially adapted for respiration, while
in Strongylocentrotus all the tube-feet have suckers.

Nervous System.— As in the starfish, there is a main nerve
ring surrounding the mouth, with five radial nerves which ac-
company the radial vessels to the base of the terminal tentacle.
Each tube-foot and all the spines and pedicellariz are supplied
with branches of these radial nerves.

The tube-feet are not only used for locomotion and respira-
tion, but are highly sensitive to various kinds of stimuli. Spe-
cialized tube-feet on the peristome enable the animal to taste.
The pedicellariz are in many species modified to perform a
variety of functions, some having specialized sense organs and
poison glands. Minute organs scattered over the body in many
species, and known as spheridia, are thought by some to act as
balancing organs.

Reproductive System.— Attached by strong mesenteries to
the upper wall of the test are the five sexual glands. The genital
duct leading from each of these glands opens by a minute pore
in the corresponding genital plate adjacent to the periproct.
When fully developed the sexual glands become enormous masses
of tiny follicles (Plate XXII).

The sexes are separate, but are not distinguishable externally.
The females produce many thousand eggs, which are discharged
into the water when mature.

Comparison of Arbacia with other Genera.— A comparison
of our three other representatives of this class with the descrip-
tion given above for Arbacia offers many points of interest.

The green sea-urchin agrees with the purple sea-urchin in
having a nearly hemispherical test, with the mouth placed sym-
metrically at one pole and the anal opening at the other. Both
species therefore belong to the order Regularia, or radially sym-
metrical urchins. Both the sand-dollar and the key-hole urchin,
on the other hand, have flat, discoid bodies, nearly circular in out-
line but with one or more slight indentations; and the key-hole
urchin has five narrow oval perforations (Plate XXVIII).

In the sand-dollar and the key-hole urchin, the mouth occu-
pies the usual position in the center of the oral surface; but in
the sand-dollar the anus has been shifted to the edge of the
92 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.

disk (Plate XXIII), and in the key-hole urchin it is very near
the mouth, on the proximal border of the middle lunule (Plate
XXIV, fig. 1). In neither of these forms, therefore, is the body
radially symmetrical, and they belong to the order Clypeastroidea,
or disk-urchins, as they may be called.

Both these species of clypeastroids have strong jaws, with fine,
sharp, calcareous teeth, but the jaws (Plate XXIV) are less com-
plicated than in the order Regularia. The peristome is very
small, so that the jaws cannot be opened so widely as in the reg-
ular forms. By means of the teeth both these species pick up
particles of sand and mud, with the diatoms and other minute
organisms adhering. These particles are swallowed in vast num-
bers, and the organic matter digested out, after which the sand is
passed out of the anal opening.

Both of our species of disk-urchins are plainly bilaterally sym-
metrical, the mouth and anus lying in the median antero-posterior
plane. This bilaterality is shown also in the outline of the body.
As illustrated in Plate XXIV, the anus in Echinarachnius lies in
an indentation at the posterior end of the disk, and there are two
other slight indentations on the edge of the disk in the adjacent
ambulacral areas. In Mellita (Plate XXVIII) the manifestation
of bilateral symmetry is carried still farther, for here there are
five symmetrically placed lunules, one being in the posterior inter-
radius, while the others occupy the two adjacent radii on each
side. These arise in the young urchins as notches in the edges
of the test, and gradually deepen and close over as the animal
increases in size. Furthermore in both species the disk is
broader posteriorly, and narrower in front.

Although the anal opening has moved from its primitive
position at the aboral pole, the ocular and genital plates have
retained the same position as in the regular sea-urchins. They

 

 

EXPLANATION OF PLaTeE XXIII. Skeleton of Disk-urchin, Echinarachnius
parma, (Natural size.)

Aboral and oral surfaces with spines removed. The upper figure shows
the ambulacral areas (“petals”) and the four genital pores near the
center of the disk. The lower figure shows the mouth and teeth, and the
closely fitted plates. The indentation on the lower median border indicates
the position of the anus, .

(Photographs loaned by the U. S. Fish Commission, with permission of
Dr. H. L, Clark.)
 

 

 

 

 

 

 

 

PLATE XXIII. Skeleton of Disk-urchin, kchiénarachnsus
parma, (Natural size.)

 

 
No. 109.] ECHINODERMS OF CONNECTICUT. 93

here surround a single central plate, however, instead of the
intestinal opening.

The ambulacral areas are plainly marked on the aboral sur-
face of both species by the rows of respiratory tube-feet which
are arranged symmetrically about the central plate. The figure
thus formed has the general shape of a five-petaled flower
(Plates XXVIT and XXVIII), and the two groups of each ambu-
lacral area are together called a “petal.” The petals are even
more clearly indicated by the rows of double pores on the surface
of the disk after the removal of the spines (Fig. 14). 7

 

Fic. 14. Echinarachnius parma. Outline
of plates on aboral surface; amb, ambulacral
areas; inter, interambulacral areas; a, position
of intestinal opening. The four genital pores
are shown near the center of the disk.

In contrast with the large spines of our regular sea-urchins,
the disk-urchins are clothed everywhere with minute, slender,
brownish or purplish spines, those on the upper surface being cov-
ered with cilia, which cause currents of water to pass continually
over the respiratory tube-feet.

The tube-feet in the clypeastroids are specialized either for
respiration or locomotion. Those serving the latter function are
scattered all over the upper surface in the interambulacral areas
as well as in the ordinary position in the ambulacral areas. On
the ventral surface they occur along definite grooves in the am-

bulacral areas, with branches extending into the interambulacral
areas. ‘
94 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. (Bull.

The respiratory tube-feet which mark the outlines of the
petals, as stated above, are much larger than the others, and
are bilobed at the base, with two fine tubes which pass through
the plates of the test in the double pores of the petal. Both kinds
of tube-feet bear suckers.

Correlated with this highly modified arrangement of the tube-
feet is a corresponding specialization of the water-vascular sys-
tem, for each foot is connected with a branch of these vessels.

MacBride* offers the following explanation of this complex
system: “ The condition of the water-vascular system is to be
explained entirely by the peculiar environment of the animal.
The demand for specialized respiratory organs is brought about
by the habit of living half buried in the sand. Under these
circumstances the strain of supplying the needful oxygen is
thrown on the dorsal tube-feet, and they become modified in
order to fit them for this function. The locomotor tube-feet are
very small and feeble compared with those of Echinus esculentus ;
but this is comprehensible when it is recollected how little resist-
ance the yielding sand would offer to the pull of a powerful
tube-foot like that of the regular urchins, for in order to move
the creature through the sand a multitude of feeble pulls dis-
tributed all over its surface is necessary, and the locomotor tube-
feet are exactly fitted, both as to size and number, for this
object.” The power of movement is not wholly dependent
upon the action of the tube-feet, however, for the vast number
of minute spines which cover the body are freely movable and
undoubtedly aid largely in the process of locomotion.

The structural weakness due to the flattened shape of the
body in the disk-like urchins is compensated by strong vertical
plates of calcareous material which unite the oral and aboral
parts of the test so firmly, especially towards the edges, that it is
difficult to break open the body except in its central portion.

Internal Anatomy.— The alimentary canal shows consid-
erable modification in the disk-urchins, owing to the nature of
the food and the position of the anal opening. Dissections show-
ing the digestive tracts of the sand-dollar and the key-hole
, urchin are illustrated on Plate XXIV.

* Cambridge Natural History, Echinodermata, page 547.
 

ot

PLATE*XXIV. Anatomy of Disk-urchins, dZe//cta Bentapora and Echina-
rachnius parma,
No. 19.] ECHINODERMS OF CONNECTICUT. 95

The reproductive organs are likewise modified, for the pres-
ence of the anus in the posterior interradius prevents the develop-
ment of the gonad which in the regular urchins occupies this
position. There are thus only two pairs of gonads developed in
the adult with four symmetrical openings on the plates at the
apical pole of the test, as shown in Fig. 14.

In the key-hole urchin the mouth lies near the center of the
oral surface, as in the sea-urchin and sand-dollar, but the position
of the anus is different from that which is found in any other
echinoderm of the region, being likewise situated on the oral
surface, and only a short distance posterior to the mouth (Plate
XXIV, fig. 1).

The mouth is provided with five massive jaws, each
ending in a sharply pointed tooth. The esophagus (Plate
XXIV, fig. 1) leads towards the aboral surface, and then bends
sharply anteriorly until it reaches the circle of supporting plates
which surround the jaws. It then divides, as in Arbacia, into
two branches, one of which forms the broad, flat stomach, while
the other, which is closely attached to the inner margin of the
stomach, is known as the siphon. The stomach (st) is just
broad enough to occupy all the space between the inner circle
of supporting plates and the outer system of plates which pass
between the oral and aboral surfaces of the body.

The outer margin of the stomach is, as in Arbacia, provided
with numerous sac-like lobes which greatly increase the secretory
surface.

 

 

ExpPLaNaTION OF PLATE XXIV. Anatomy of Disk-urchins, Mellita and
Echinarachnius.

Fig. 1. Mellita pentapora. Dissection of body to show alimentory canal.
The slender esophagus leads from the centrally placed
mouth (surrounded by five large jaws) to the broad stomach
(st) and siphon (siph). The convoluted intestine (int), fol-
lows the definite course indicated, and passes gradually into the
rectum (7), which opens through the anus (a) situated between
the mouth and the median lunule. In some specimens the anus
is placed at the inner end of the lunule. The five lunules (/)
are shown.

Fig. 2. Echinarachnius parma. Dissection of the body to show alimentary
canal; e, esophagus; st, stomach; siph, siphon; int, intestine;
r, retum, opening on oral surface near margin of disk; s. c¢,
madreporic canal. The five angular jaws are situated sym-
metrically about the mouth.
96 CONNECTICUT GEOL. AND NAT. HIST, SURVEY. [ Bull.

The stomach completes a half-circle of the body cavity in
the left-handed direction, as seen from the aboral side, and is
then joined by the narrow siphon mentioned above. At this
point the intestine begins, and this organ bends sharply towards
the mouth in order to pass between the jaws and the posterior
lunule.

In the right half of the body the intestine bends sharply pos-
teriorly beside the posterior lunule and runs in a series of broad
loops nearly half-way around the body or nearly to the middie
line anteriorly. It then bends sharply back on itself, occupying
a position between the inner and middle series of supporting
plates, and returns to the middle line between the mouth and the
posterior lunule. On reaching a position near the middle line, the
intestine changes into a narrow tube, the rectum (Plate XXIV,
fig. 1, 7), which crosses the first portion of the intestine on the
aboral side, and then bends sharply to open to the exterior be-
tween the anterior border of the posterior lunule and the mouth.

The siphon referred to above as lying along the inner border
of the stomach, is a narrow tube which makes a short passage
between the two ends of that organ. By means of this siphon
water can be taken in at the mouth and passed back directly to
the intestine without interfering with the digestive juices of the
stomach. The water thus introduced is said to serve a’respira-
tory function in furnishing a supply of oxygen to the viscera.

In both the key-hole urchin and the sand-dollar, the posterior
portion of the stomach and the whole of the intestine are com-
monly filled with a mass of fine sand and mud, abounding in
diatom shells. This is sufficient indication that the food of these
animals consists largely of such microscopic particles of organic
matter as occur in the mud or adhering to the grains of sand.
These particles doubtless include many kinds of living and dead
organisms among which diatoms and other minute alge are
abundant.

If a fresh or well preserved sand-dollar be opened by care-
fully breaking away the plates of the aboral surface the internal
organs are easily studied. The four brownish purple ovaries or
spermaries are attached to the aboral plates. After these are
removed the alimentary canal lies freely exposed.
No. 19.] ECHINODERMS OF CONNECTICUT. 97

The digestive system of the sand-dollar (Plate XXIV, fig.
2) is essentially similar to that described for the key-hole urchin,
with the exception that the rectum opens to the exterior near the
edge of the disk, and is on that account longer than in the latter
species.

The short esophagus leads from the large jaws surrounding
the mouth to the broad flat stomach. In life the stomach is
green in color, with a smooth inner border (Plate XXIV, fig. 2),
while its outer border is provided with many lobes of brownish
color. A narrow siphon extends along the inner border, as in
the key-hole urchin. The intestine nearly completes the wide
circle, of which the stomach forms a part, and then bends sharply
on itself to pass posteriorly, with many short bends, to the open-
ing near the edge of the disk. The opening is sometimes almost
exactly on the margin, but is more often placed near the edge of
the oral surface. In young individuals it is on the aboral
surface.

HABITS

The four species of Echinoids which are found in Connecticut
waters exhibit much diversity of habit, associated with differen-
tiations of structure. The two species belonging to the order
Regularia—the purple sea-urchin and green sea-urchin — are
provided with large spines for protection and locomotion, and live
free upon the surface of rocks, sand, shells, and other objects
found upon the bottom of the sea. Between tides they often
inhabit the tide pools in the rocks, hiding away in crevices and’
beneath seaweeds, often clinging to the frond of the seaweed
itself and sometimes drawing it over the body as a protective
covering. The two species of clypeastroids—the sand-dollar
and the key-hole urchin,— on the other hand, are covered every-
where with extremely minute spines, and they live partly buried
beneath the surface of the sand.

Locomotion.— The regular sea-urchins move about from
place to place both by the movements of the spines and by the
action of the very long tube-feet. Both sets of organs commonly
assist in the process. Certain species make the greatest use of
the spines in locomotion, while the tube-feet of other forms are
the most efficient. In exceptional cases the former are said

7
s

98 CONNECTICUT GEOL, AND NAT. HIST. SURVEY. [Bull.

to be able to move rapidly without making any use of the tube-
feet, and the latter to walk with the tube-feet exclusively without
touching the spines to the object on which they are moving. The
sand-dollar and key-hole urchin move through the sand by the
actions both of the minute spines and of vast numbers of suck-
ing tube-feet on both upper and lower surfaces of the disk-like
body. These hundreds of tube-feet attach themselves to the
particles of sand, and by their combined action draw the body
forward, the minute spines aiding in the process.

The regular urchins can easily right themselves from any
position in the water by the combined action of tube-feet and
spines. The disk-urchins, on the other hand, can only right
themselves after they have buried their bodies in the sand.

Locomotion in any direction is accomplished with equal ease
by the regular urchins, while the disk urchins ordinarily move
with the portion of the disk which bears the intestinal opening
backward.

» The behavior of various species of echinoids under a great
variety of conditions has been studied extensively by numerous
investigators. In the popular book by Romanes,* and in a recent
book by Von Uexkiill,t may be found most interesting accounts
of the performances of these fascinating creatures.

The bodies of all species must be kept clean, and for this
purpose special provision is made. In both the green and the
purple urchin the intestinal opening is in the center of the upper
surface. Conscquently when the refuse matter is discharged it
tends to fall directly upon the surface of the body. In the green
urchin this region is thickly studded with minute movable spines
and pedicellarie which can be moved in such a way as to pass
any foreign particles from one to the next nearer the border of
the test, so that such particles are quickly cast away from the
body. The tube-feet also aid in the cleaning process.

Elizabeth and Alexander Agassiz{ describe this action of the
pedicellariz in the following words:— “If we watch the sea-
urchin after he has been feeding, we shall learn at least one of
the offices which this singular organ performs in the general
economy of the animal. That part of his food which he ejects

* Jellyfish, Starfish, and Sea-Urchins.,
{ Umwelt und Innenwelt der Tiere.
} Seaside Studies in Natural History, page ros.
No. 19.] ECHINODERMS OF CONNECTICUT. 99

passes out at an opening on the summit of the body, in the
small area where all the zones converge. The rejected particle
is received on one of these little forks, which closes upon it like
a forceps, and it is passed on from one to the other, down the
side of the body, till it is dropped off into the water. Nothing
is more curious and entertaining than to watch the neatness and
accuracy with which this process is performed. One may see
the rejected bits of food passing rapidly along the lines upon
which these pedicellarize occur in greatest number, as if they were
so many little roads for conveying away of the refuse matters;
nor do the forks cease from their labor till the surface of the
animal is completely clean, and free from any foreign substance.
Were it not for this apparatus the food thus rejected would be
entangled among the tentacles and spines, and be stranded there
till the motion of the water washed it away.”

In the purple urchin the aboral area is devoid of spines, and
so smooth that refuse matter or foreign particles which fall upon
it will be easily washed away by currents of water or by the
movements of the animal.

In the disk-urchins the intestinal opening is placed at the edge
of the disk or on the lower surface, so that the fecal matter
does not fall upon the body. Furthermore the spines are covered
with cilia, and these create a current of clean water which con-
stantly flows past the animal and washes away any very minute
foreign particles. The movements of the minute spines and tube-
feet brush away any particles which are not thus removed.

Food.— The regular urchins feed largely upon seaweeds, but
also devour any dead animal matter obtainable and supplement
their diet by the diatoms and such other minute organisms as
are found upon the bottom on which the animals live. Much
. sand and mud is swallowed for the organic matter in it. The
disk-urchins swallow great quantities of sand, with such diatoms
and other minute organisms as it contains.

Natural enemies.— Many kinds of fishes feed upon all our
species of echinoids, in spite of their covering of spines, and the
free-swimming embryos are subject to the attacks of still other
species of fishes.
100 CONNECTICUT GEOL, AND NAT. HIST. SURVEY. (Bull.

REPRODUCTION

In the class Echinoidea there are no species which are capable
of asexual reproduction, such as occurs in some of the Asteroidea,
the production of eggs which require fertilization being the only
means of reproduction in this class.

The echinoids are of separate sexes, although it is impossible
to distinguish the males from the females externally. Each
female discharges vast numbers of eggs into the water during the
breeding season of each year of her life. In one of the foreign
species a large female may produce twenty million eggs yearly.
Owing to the gregarious habits of the animals, the eggs stand a
reasonable chance of being fertilized by the sperm cells which
are discharged in enormous numbers by the male urchins at the
same season.

It often happens, as is also the case with the starfish, that
certain animals fail to mature and discharge their sexual products
at the normal season, but eggs discharged at other periods of the
year must almost always fail of fertilization or development.

The eggs are so numerous and easily obtained that they have
become classical objects for the study of the processes of fertili-
zation and early development. The suggestions on page 50 re-
garding the study of starfish eggs will be found equally appro-
priate for those of the urchins.

DEVELOPMENT

As illustrated by Fig. 15, the immature eggs in the ovary of
the urchin are each provided with a large germinal vesicle.
After the two polar bodies are formed, the egg is discharged into
the water; it then settles slowly to the bottom and is ready for
fertilization. A single sperm cell, which may be swimming about
in the water in the vicinity, may enter the egg. After such union
the fertilized egg divides regularly into 2, 4, 8, and 16 cells,
called blastomeres, as illustrated in Fig. 15.

These divisions take place very rapidly, the first cleavage
occurring in about an hour and a quarter after fertilization, and
succeeding cleavages at intervals of an hour or less.

A hollow sphere of cells known as the blastula is then formed.
In about twelve hours after fertilization the blastula becomes
 

 

Fic. 15. Cleavage of egg of Sea-urchin. 1, egg from ovary; 2,
mature egg with the two minute polar bodies; 3, fertilization; 4 to 6,
first cleavage, forming two blastomeres; 7, 8, second cleavage, with 4
blastomeres; 9, 10, third cleavage, with 8 blastomeres; i1, fourth cleavage,
with 16 blastomeres; 12, section of blastula. The blastula soon becomes
covered with cilia and swims actively about in the water. (After Wilson.)
102 CONNECTICUT GEOL, AND NAT. HIST. SURVEY. [Bull.

covered with vibrating cilia, and the embryo swims round and
round within the egg membrane. This membrane soon bursts,
and the free-swimming blastula rises from the sea bottom to
swim at the surface of the water.

 

Fic. 16. Free-swimming larva (pluteus)
of the purple sea-urchin, Arbacia punctulata.
The deeply shaded portions represent the cal-
i careous skeletal rods in the four pairs of
arms. ‘The primitive mouth, stomach, and
intestine occupy the central portions of the
body. (After Weysse.)

After an infolding of the cells on one side to form a mouth
and a primitive alimentary canal, a complicated series of changes
in the embryo occurs. It finally assumes the shape of a helmet,
with long projecting arms, and bands of very long cilia. It now
swims freely about, usually in company with millions of others,
and begins to feed upon the minute organisms living at the
surface of the sea. The embryo, or larva, is now bilaterally
No. 19.] ECHINODERMS OF CONNECTICUT. 103

symmetrical, with both mouth and anus, and is known as a pluteus
(Fig. 16). It bears absolutely no resemblance to the adult
urchin. The free-swimming pluteus lives and feeds at the sur-
face for a period of several weeks, the time depending some-
what on the temperature and other conditions, and varying in
different species. In this time it may have been carried by cur-
rents and tides to a considerable distance from its place of origin.

 

Fic. 17. Arbacia punctulata. Side
view of young urchin immediately after
the metamorphosis. The spines re-
maining from the pluteus are in process
of absorption. (After Brooks.)

°

When ready to assume the adult form, the pluteus settles to
the bottom, absorbs its larval organs, and by a complicated meta-
morphosis assumes the condition of a young urchin (Figs. 17
and 18). The young urchin differs from the adult in having
the whole upper surface covered by the plates which will event-
ually form only the periproct of the adult, and by the relatively
enormous tube-feet. The animal is now radially symmetrical, and
creeps about on the sea bottom after the manner of the adult
urchin. It feeds upon diatoms and other minute organisms until,
104. CONNECTICUT GEOL. AND NAT. HIST, SURVEY. {Bull.

by its further growth, and the development of plates and spines,
it is able to assume the habits of the adult.

 

Fic. 18. Arbacia punctulata. Oral
surface of young urchin shortly after
the metamorphosis. (After Brooks.)

The clypeastroids pass through stages very similar to those
of the regular sea-urchins. The sand-dollar, for example, de-
velops from a long-armed pluteus, which settles to the sand at the
sea bottom and gives rise to the young sand-dollar. This has at
first a few relatively long spines and large tube-feet. There is
now a nearly complete radial symmetry, the intestinal opening
at this stage being near the center of the upper surface, some-
what as in the regular urchins. With the further growth of the
animal, its bilateral symmetry becomes more marked, and the
anus is gradually shifted to its final position near or beneath the
edge of the disk.

Grave* has been successful in rearing large numbers of the
key-hole urchin from the fertilized eggs, and following their
transformations to the adult form. The egg of this species

*C. Grave. Biol. Bulletin, vol. v, 1903.
No. 19.] ECHINODERMS OF CONNECTICUT. 105

likewise develops into a long-armed pluteus, and this by a com-
plicated metamorphosis gives rise to the bizarre creature shown in
Fig. 19, which actually represents the young urchin, although it

 

Fic. 19. Mellita pentapora. Young urchin shortly
after the metamorphosis from the free-swimming
pluteus. The pentagonal area in the center represents
the mouth, in the angles of which are the five teeth.
The spines and tube-feet are at this stage of enor-
mous size relative to the size of the body. (After
Grave.)

differs widely in appearance from the adult. The oval body is
provided with a small number of spines and tube-feet of relatively
106 CONNECTICUT GEOL, AND NAT. HIST. SURVEY. [Bull.

enormous size. By means of the tube-feet the creature clings
to the objects on which it rests and crawls slowly about. In
the center of the body is the pentagonal mouth with the five
calcareous teeth, and extending across the body are three bands
of cilia which are thought to serve in sweeping towards the
mouth the small particles of organic matter on which the animal
feeds. With the increase in size of the body the ciliated bands
disappear, and the now relatively minute tube-feet convey the
food to the mouth. As the disk-like body of the animal increases
further in size, the anal opening, which is at first on the aboral
surface, is gradually shifted to the edge of the disk. The en-
largement of the disk now becomes interrupted at certain points
on the periphery, causing five notches in the margin. By con-
tinued growth of the intervening portions the notches become
elongated, and their edges close together and unite distally, to
form the characteristic lunules.

KEY TO SPECIES

The echinoids of the world are divided into three orders: (1)
Regularia, including the hemispherical sea-urchins; (2) Cly-
peastroidea, including the flat and disk-like forms; and (3)
Spatangoidea, or heart-urchins.

The two first orders only are found in Connecticut waters,
and of these there are four representatives; two, the purple sea-
urchin and the green sea-urchin, belonging to the Regularia, and
two, the sand-dollar and the key-hole urchin, to the Clypeas-
troidea. They may be easily distinguished by the following
characters : —

1. Body nearly hemispherical, spines rather large, anal opening

Bt ADOTAL POLE wie oe crave eri ese eam sue axe} £08) Fe Snare) ave dada ance 2

Body flat and disk-shaped, spines small, anal opening ec-
CONTIG sade ean ee eA ue De aideta aah ee eee 3

2. Spines long, absent near aboral pole...Arbacia punctulata
‘Spines short, covering aboral pole..................0.00, ‘
Strongylocentrotus drébachiensis

3. Test without perforations........,.Echinarachnius parma
Test with five narrow perforations (lunules)..............

Mellita pentapora
Missing Page
'

No. 19.] ECHINODERMS OF CONNECTICUT. 107

Arbacia punctulata (Lamarck)
Purple Sea-urchin
Plates XX, XXII, XXV.

This is the only species of the regular sea-urchins common in
the greater part of Long Island Sound. It is widely distributed,
but occurs in abundance only in restricted localities. It prefers
shelly or rocky bottoms, and is. often dredged from the oyster
beds. It sometimes occurs between tides in the tide pools in
rocky places, hiding in crevices or beneath seaweeds.

The species occurs in shallow water along the coast from
Cape Cod to the Gulf of Mexico. There is great variation in
the abundance of individuals of this species in the same locality
in different years. At the Biological Laboratories at Woods
Hole, Mass., large numbers of these ‘urchins are desired for
embryological and experimental studies each year, and, while
in some years the species can be found in unlimited numbers,
in other years it is extremely difficult to secure a supply. On
the oyster beds off New Haven Harbor, there seems to be a
similar variation in numbers.

The purple sea-urchin is commonly from one to two inches
in diameter, excluding the spines. The spines are heavy and
solid, and measure from one-half to one inch in length. Each
is fluted longitudinally, and, while some of the upper ones are
acutely pointed, others are blunt. Towards the oral surface
they become shorter and flattened at the tip. They are usually
of a purplish color. The test is likewise reddish, purple, or
purplish brown, while the tube-feet are red or brown.

 

 

EXPLANATION oF PLate XXV.' Purple Sea-urchin, Arbacia punctulata.
(Natural size.)

Fig. 1. Aboral surface of test with spines removed, showing arrange-
ment of plates. The five double rows of dotted plates represent
the ambulacral areas, while the intervening rows of plates
comprise the interambulacral areas. The four plates at the
center form the periproct. Each of the interambulacral areas
ends in a plate with a small perforation, the genital pore. One
of these plates is somewhat larger than the others and serves
as the madreporic plate. ~ 1

Fig. 2. Side view of test. : : ahi

Fig. 3. Oral surface of test, showing the large opening covered in life
by the peristome. ; ots ; —

(From photographs loaned by the U. S. Fish Commission, with permission

of Dr. H. L. Clark.)
108 CONNECTICUT GEOL, AND NAT. HIST. SURVEY. [Bull.

The aboral pole is free from spines for a considerable dis-
tance; not only are the plates of the periproct and the genital
plates naked, but spines are likewise absent from the middle of
the interambulacral areas for a distance nearly half-way to the
equator of the test. Only the large primary spines are present.
They are arranged in a double series in each ambulacral area,
and in four to eight or more series in each interambulacral area.
There are five pairs of prominent buccal plates.

In Connecticut waters the sexual products are matured in
early summer. The eggs contain particles of the purplish pig-
ment which permeates nearly all the tissues of the body. They
are admirable objects for the study of the processes of fertili-
zation, cleavage, and early embryonic development.

For such a study the suggestions given for the examination
of the starfish egg will apply equally well. The free-swimming
embryo, known as the pluteus, may be kept alive for a number
of days, but nearly all attempts to rear artificially to the adult
form have failed.

Strongylocentrotus drdbachiensis (O. F. Miller)

Green Sea-urchin
Plates XXI, XXVI.

This is a typical circumpolar species, occurring in great
abundance north of Cape Cod, and is found but locally in Con-
necticut waters. It extends southward in the deep water off our
coast as far as New Jersey, but south of Cape Cod it is of
much smaller size than northward.

In Long Island Sound small specimens have been dredged off
New Haven and Stratford; but these individuals or their an-
cestors have presumably been carried in their early stages by the

 

 

EXPLANATION OF PLaTE XXVI. Green Sea-urchin, Strongylocentrotus
drébachiensis. (Natural size.) ‘

The upper figure shows the aboral surface, thickly covered with the
primary and secondary spines.

In the center of the aboral surface (lower figure) is seen the peristome
with the five sharp white teeth which close the mouth. Between the
spines are shown the five double rows of slender tube-feet with enlarged
terminal sucking disks.

(Photographs loaned by the U. S. Fish Commission, with permission of
Dr. H. L. Clark.)
 

 

 

 

 

 

 

PLATE XXVI. Green Sea-urchin, Strong ylocentrotus dro-
bachicnsts. (Natural size.)

 

 
No. 19.] ECHINODERMS OF CONNECTICUT. 109

westward currents from the colder and deeper waters nearer the
eastern portion of the Sound. Specimens have been taken near
the Thimble Islands and near Faulkner’s Island. Off New
London and eastward to Watch Hill, Rhode Island, the individ-

uals become increasingly abundant and of larger size. The
. species also occurs on the northern coasts of Europe, the north
coast of Siberia, and on both sides of the northern Pacific
Ocean and Bering Sea, southward to Kamchatka on the west
and Puget Sound on the east.

The species prefers rocky bottoms, the food consisting largely
of algee growing upon the rocks. Mud containing diatoms and
other minute organisms is swallowed in abundance, and any dead
animal is greedily devoured. Even the bones of a dead fish will
be cut away with the sharp teeth and completely devoured.

Farther to the north the species lives in great abundance be-
tween tides. In the southern part of its range it may reach a
depth of more than 600 fathoms.

Individuals of this species grow to a larger size than do those
of the purple urchin, the diameter of the test measuring from
two to three inches in large specimens.* The test is rather flat-
tened, being about half as high as broad. The spines are ex-
ceedingly numerous, but are small and short, the largest being
only about a half-inch in length.

The peristome measures from three-fourths to one inch in
diameter, and is proportionally larger in young than in mature
individuals. The anal plates are numerous and very small in
full-grown specimens.

The color in life is greenish, varying in shade in different
individuals and often on different parts of the body. Many
specimens have the zones bearing the tube-feet much lighter in
shade than the interambulacral areas. In many there is a yel-
low, red, or purple tinge, due to variations in the coloration of
the spines; and in some these shades are intensified, the spines
being tipped with deep red, purple, or violet. The miliary spines,
pedicellariz, and tube-feet are whitish or pale violet.

The species differs from Arbacia punctulata in that all the
plates of the aboral pole bear minute protective spines. The
larger spines of the test are longitudinally fluted and pointed at
the tip. They are arranged in a double series on each ambulacral

_ "Several very large specimens in the Yale University Museum exceed four
inches in diameter,
110 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. (Bull.

and interambulacral area. Scattered thickly among the primary
spines are much smaller, secondary, spines of similar shape,
while a third variety, the miliary spines, are still smaller and very
slender. There are five pairs of buccal plates, which bear miliary
spines. The comparative sizes of the spines and their arrange-
ment are well shown by the tubercles on the test (Plate XXI).
Several kinds of large fishes, including the wolf-fish, swallow
the adult animals whole, quite disregarding the sharp spines
which cover the body. The young have still more numerous
enemies among the fishes, and the free-swimming plutei are
swallowed in great numbers by surface-feeding fishes.

Echinarachnius parma (Lamarck)
Sand-dollar

Plate XXIII; Plate XXIV, fig. 2; Plate XXVII.

The sand-dollar is a most interesting little creature because
of its peculiar modifications to meet the requirements of the
environment under which it lives. It is sometimes very abun-
dant on sandy bottoms off shore, where it lives partly buried
beneath the surface of the loose sand. The body is covered with
a multitude of tiny suckers, by means of which the creature
creeps slowly along, devouring as it goes particles of sand with the
numerous microscopic organisms, particularly diatoms and other
alge, which are found among them.

~ The much flattened, disk-like body is well adapted for with-
standing any tendency to be rolled over or thrown upside down
by the shifting of the sand under the influence of the waves.
It is very probable, moreover, that the animal can penetrate
deeper into the sand when the water becomes very rough, to
return to the surface again after the disturbance is over.

The species has a remarkable range of distribution. It is
found along the Atlantic coast from Labrador to New Jersey, and

 

 

EXPLANATION oF PLaTE XXVII. Echinarachnius parma. Aboral and
oral surfaces. (Natural size.)

The aboral surface, upper figure, shows the minute spines and the
darker ambulacral areas, “petals”. The oral surface, lower figure, shows
the ambulacral areas as narrow furrows radiating from the centrally
placed mouth and branching on each side toward the margin. These
areas are nearly devoid of spines. A cluster of less slender spines sur-
rounds the mouth. :
Missing Page
No. 19.] ECHINODERMS OF CONNECTICUT. IIl

on both sides of the Pacific Ocean, extending from the Aleutian
Islands along the American shore as far south as British Columbia
and on the Asiatic shore southward to Japan. In the more
northern parts of its wide range it is found near low-water mark,
but farther south it occurs only in deeper water. It has been
collected from a depth of more than eight hundred fathoms.

The color of the body in life is usually purplish brown or
reddish brown, some specimens inclining to purple while others
are distinctly red. When young, a paler red color predominates.
Many individuals have the ambulacral areas darker red than the
remainder of the body. In alcohol, the color changes to a dark
green or brown, and the alcohol dissolves so much of the pig-
ment as to become deeply colored. Dried specimens are likewise
dark green or brown. Verrill states that the fishermen sometimes
made an indelible marking ink by grinding up the skins and
spines of these animals and mixing with water.

The body is nearly circular in outline, but is indented at one
point, which indicates the position of the anus. The surface of
the body is everywhere thickly covered with minute spines (Plate
XXVIT), so delicate and closely placed as to form a velvety
covering.

On the aboral surface the ambulacral areas are plainly marked
by the position of the respiratory tube-feet. These areas are
symmetrically placed about the central plate, and constitute the
so-called petals.

In the test after the removal of the spines (Fig. 14), the
‘position of the petals is clearly shown as forming the aboral ends
of the ambulacral areas (amb). The interambulacral areas like-
wise bear tube-feet, but they are here much smaller than those of
the petals. At the tips of the ambulacral areas the position of the
terminal tentacle is indicated, and between them the four openings
of the genital glands.

On the oral surface the ambulacral areas are marked by fur-
rows (Plate XXVII). The peristome is very small (Plate
XXIII), although the five calcareous teeth are well developed and
very sharp.

In many localities the species is so abundant as to form an
important part of the food supply of certain fishes, particularly
of the flounder, codfish, and tautog.
E12 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.

Mellita pentapora (Gmelin)
Key-hole Urchin

Plate XXIV, fig. 1; Plate XXVIII.

The name Mellita testudinata was given to this species by
Klein in 1734; but, as this long preceded the Linnean code, the
specific name pentapora proposed by Gmelin in 1788 should be
adopted. Many authorities, however, insist upon the use of
testudinata.*

This species has a flat test, and in this respect bears a super-
ficial resemblance to the common sand-dollar, but is easily dis-
tinguished by the five narrow openings, termed lunules, which
pass completely through the body as shown on Plate XXVIII.
One of these lunules is situated in the posterior interradius, about
half-way from center to circumference, while the other four are
symmetrically placed, one in the center of each radius except the
anterior.

The flattened test is densely covered with short but slender
spines of a brownish color. The general color of the living
animal is commonly pale brown, sometimes with a tinge of green.

Especially after the spines are removed, the petaloid ambu-
lacral areas are conspicuous on the aboral surface. On the oral
surface the narrow ambulacral furrows are provided with paired
branches which extend peripherally from the mouth to the edge
of the disk. Each of the main branches has lateral offshoots
(Plate XXVIII).

*In a recent paper (Annals and Mag. Nat. Hist., 8 ser., vol. vii, 1911) Clark recom-
mends the adoption of the name quinquiesperforata Leske for this species.

 

 

EXPLANATION OF PLaTE XXVIII. Key-hole Urchin, Mellita pentapora.
(Natural size.)

Aboral and oral surfaces of two dried specimens. The minute spines
have been removed from the left-hand side of each. The aboral surface
shows three of the five ambulacral areas, “petals”. The mouth lies in
the center of the oral surface, with the anus near the inner end of the
median lynule. One of the posterior lunules in the lower figure is ab-
normal in that it remains open to the edge of the disk.
 

 

 

 

 

 

 

PLATE XXVIII. Key-hole Urchin, Mel/ita pentapora. (Natural
size.)

 
No. 19.] ECHINODERMS OF CONNECTICUT. 113

The mouth is situated a little anterior to the center of the
oral surface, while the posterior opening of the intestine lies
between the central end of the interradial lunule and the mouth.

In some specimens one or more of the lunules, as shown on
Plate XXVIII, may extend quite to the margin of the disk.
Such an abnormality may be caused either by accidental injury
or by the failure of the two edges of the lunule to unite together
distally in the young urchin.

This species occurs locally from Nantucket to Brazil in shal-
low water, although it is not common north of Cape Hatteras.
In Long Island Sound the species has been collected at Hunting-
ton, Long Island, a number of specimens from this locality
belonging to the Yale University Museum.

A description of the digestive system of this species may be
found on page 95, while Plate XXIV, fig. 1, illustrates the
internal anatomy.

In a paper by Grave* the structure and development of the
larve have been described and illustrated.

* Johns Hopkins Univ. Circular, No, 157, 1902.
114 CONNECTICUT GEOL, AND NAT. HIST. SURVEY. { Bull.

CLASS IV. HOLOTHUROIDEA

The animals included in this class are sometimes called sea-
cucumbers. They are, however, not so well known to people
other than naturalists as are the other classes, and most of them
can hardly be said to have any English names.

The six species of holothurians found along the Connecticut
coast or in reasonable proximity thereto are all limited to certain
restricted localities, and their presence in any particular spot
cannot be predicted with any considerable degree of certainty.
In general, a muddy bottom below low-water mark is favorable
for the large, brown or blackish Thyone briareus, while the others
prefer sandy localities, the two species of Syuapta occurring fre-
quently between tides, and the C ucumaria only below the ordinary
tides. The two other species, Thyone wnisemita and Thyone
scabra, have not yet been recorded from Connecticut waters, but
their presence in Narragansett Bay and near the eastern end of
Long Island Sound makes it probable that they actually occur
within the limits of the Sound, and that future investigations will
reveal their presence in these waters.

STRUCTURE

These animals have but little superficial resemblance to the
other classes of Echinoderms, although in their general anatomi-
cal structure they show their relationship. In contrast with the

 

EXPLANATION OF PLATE XXIX.

Fig. 1. Synapta roseola. Five times natural size. The two longitudinal
: ' lines represent two of the five bands .of longitudinal muscles.
Fig. 2. Tentacle of same species, with seven digits. Much enlarged.
Fig. 3. Synapta inherens, with the twelve tentacles surrounding the widely
opened mouth. The body is strongly contracted and shows
the constrictions due to action of the circular muscles. Along
the axis of the body one of the bands of longitudinal muscles
; is shown. Five times natural size.
Fig. 4. Tentacle of same ore with nine digits. Much enlarged.
Fig. 5. Thyone briareus. 'wo-thirds natural size. The dorsal surface
is toward the top of the page, the lower, rounded margin
being in the mid-ventral line.
 

PLATE XXIX. Holothurians.
No. 19.] ECHINODERMS OF CONNECTICUT. 115

hard, spiny body coverings possessed by the starfish, brittle stars,
and sea-urchins, the holothurians have soft, sac-like or worm-like
bodies (Plates XXIX, XXXI, XXXII), in the skin of which
only very small calcareous plates are found. The mouth, at one
end of the elongated body, is surrounded by a circle of branched
oral tentacles comparable with the oral tube-feet or tentacles of
the other Echinoderms. The intestine ends in a sac-like cloaca
at the end of the body opposite the mouth.

 

Fic. 20. Diagram of transverse
section of the body of a holothurian.
D, dorsal interradius; J, J’, I”, first,
second, and third sections of in-
testine attached to adjacent inter-
radii; LD, LV, RD, RV, and V, left
dorsal, left ventral, right dorsal,
right ventral, and ventral radii, res-
pectively.

The body is in most species adapted for creeping upon the
sea bottom; and, as the animal habitually creeps with the same
side uppermost, there has come about a fairly well-marked dif-
ferentiation into a ventral and a dorsal surface.

Three of the five ambulacral areas are situated upon the
ventral surface, and are usually provided with more highly
developed tube-feet, or pedicels, with sucking disks. The pedi-
cels of the two dorsal ambulacral areas are commonly modified as
delicate finger-like processes used for respiration and sensation.
In many forms, as Thyone (Plate XXXI), the pedicels are scat-
tered over the whole surface of the body, while in such burrowing
forms as Synapta there are no pedicels whatever (Plate XXIX,
figs. I, 3).

With the habit of creeping upon the side there has also come
a bilateral symmetry of the body, so that it is customary to speak
116 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. {Bull.

of the oral and aboral ends as anterior and posterior, and the
terms right and left are applied as in other bilaterally symmetrical
animals.

The body walls are very muscular, with enormously powerful
longitudinal muscles running the length of the body along the five
radii, which correspond to the ambulacral areas of the other
groups (Fig. 20). Transverse muscles serve to diminish the cir-
cumference of the body, and thus, by exerting pressure on the
fluids in the body, cause the animal to elongate. The interaction
of the two sets of muscles enables the creature to move in a
worm-like fashion.

The general anatomical features of the holothurians may be
well illustrated by a study of Thyone, as described below.

Internal Anatomy of Thyone.— Few marine invertebrates
are more satisfactory for the study of internal anatomy than the
common Thyone. For this reason the more conspicuous of its
organs will be briefly described in this place, although the details
of the water-vascular system, blood system, and nervous system,
the description of which would require more space than is here
available, must be omitted.

So powerful are the contractions of the body walls when the
animals are injured, that, unless some special precautions are
taken in killing the specimens for dissection, the body may be
ruptured, and the whole crown of tentacles and a portion of the
viscera may be ejected. A convenient method of avoiding this
trouble is to seize the living holothurian immediately behind the
tentacles with strong forceps and plunge it into boiling water.
If the experiment is successful, the tentacles will remain partially
expanded, and the body walls intact.

For a study of the internal organs, the body should be opened
with scissors along the whole length of the ventral surface.

On opening the body, the viscera are found to be situated in a
large central cavity, the body cavity, or cceelom. In life the
space between the viscera and the body walls is filled with the
coelomic fluid.

Alimentary canal.— Of the ten branched tentacles which
surround the mouth, two are much smaller than the others, and
will serve to indicate the ventral side of the body (Plate XXX).
If a slit is made through the ventral body wall throughout the
 

co -¢l. ap.

PLATE XXX. Anatomy of Holothurian, Thyone briareus,
No. 19.] ECHINODERMS OF CONNECTICUT. 117

length of the body, and the cut walls folded and pinned back,
the arrangement of the internal organs is plainly visible.

In the spacious body cavity lie the much coiled intestine, the
profusely branched respiratory trees, the Polian vesicles, the
madreporic canal, and other organs, as shown on Plate XXX.

At the anterior end of the body the slender esophagus leads
from the region of the calcareous ring at the base of the tentacles
back to the sac-like stomach. The walls of the stomach are
highly muscular and much thicker than the other parts of the
alimentary canal. At its posterior end the stomach becomes much
narrowed, and leads into the long and much coiled intestine.
The total length of the intestine is several times that of the
body. It is arranged in three broad loops, each of which is in
itself much convoluted (Plate XXX). The first section leads
with many folds posteriorly (near the mid-dorsal line) to the
dorsal side of the cloaca. Here there is a sharp bend with several
convolutions, and the second section leads forward (on the left
dorsal side) to the anterior half of the body. After several
further twists back and forth through the ccelomic space, the
third section leads posteriorly (on the right ventral side) to

 

 

EXPLANATION OF Plate XXX. Anatomy of Holothurian, Thyone briareus.
(Twice natural size.)

The body has been opened on the ventral side by a longitudinal in-
cision extending the whole length of the animal in the right ventral inter-
radius. The body walls and viscera are spread symmetrically on both sides.
In the crown of tentacles (¢) are seen the two smaller ventral tentacles (#).
From the calcareous ring beneath the tentacles, the slender esophagus
(e) leads into the saclike stomach (st), and thence into the intestine.
The intestinal convolutions are not represented in exactly their natural
positions, but it is possible to distinguish the three main sections (i. 1,
t, 2, and 1, 3) of this canal. The intestine is attached to the body walls
by strong mesenteries, of which only one (mes), connected with the
posterior section of the intestine, is represented. The cloaca (cl) is con-
nected with the body walls by strong muscles (cl. m); its connection
with the exterior through the cloacal aperture (cl. ap) is shown. From
the anterior end of the cloaca the pair of profusely branched respiratory
trees (7. t) extend nearly to the anterior end of the body cavity. The
slender filaments of the sexual gland (g) lead to a narrow genital duct
(g. d), which opens on the dorsal side of the body between the bases
of the dorsal tentacles. The five pairs of powerful longitudinal muscles
(1. m.), which mark the five radii of the body, connect anteriorly with
the equally strong retractor muscles (r. m) of the peristome. At
the base of the calcareous ring (c. 7), beneath the tentacles, the ring
canal (r. c) of the water-vascular system is seen. This canal is con-
nected with the large saclike Polian vesicles (P. v), and the slender
madreporic canal (s. c), the latter ending in a small madreporic plate.
118 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. {Bull.

open into the anterior end of the broad, muscular cloaca. The
intestine is supported by three mesenteries, attached to the cor-
responding interradii. Thus the proximal section is attached
along the greater part of the length of the mid-dorsal interradius,
the second section to the left dorsal interradius, and the last
section to the right ventral interradius, as shown in Fig. 20.
In its total length the intestine describes a partial spiral turn
around the main axis of the body, as is easily seen by the position
of the attachment of the mesenteries.

The mesentery attaching the third section to the right ventral
interradius is shown on Plate XXX.*

Calcareous Ring.— Surrounding the anterior end of the
esophagus, and forming a support for the oral tentacles, is a
broad calcareous ring, consisting of five radial and five inter-
radial plates. The radial plates are notched anteriorly for the
passage of the radial nerve and have two long posterior projec-
tions, while the interradial plates are much simpler.

Cloaca.— The cloaca serves not only for the discharge of
waste substances from the alimentary canal, but also has a most
important respiratory function as described below. It is in
sharp contrast with the extremely thin walled intestine in that
it is provided with very powerful circular and radiating muscles.
The former surround the cloaca closely, while the latter branch
out radially and pass directly through the ccelom in all directions
to connect the cloaca with the adjacent body walls (Plate XXX).
The contraction of these radiating muscles causes the cloaca to
open widely, while the circular muscles serve to close it. When
the cloaca is opened, water rushes in from the outside through the
cloacal aperture, and is thus forced up into the respiratory trees.

The cloacal opening is supported by a narrow ring of cal-
careous plates, with five posterior projections, termed “ anal

* Since the animal is represented as opened along the ventral side, the organs on
the left side of the body are seen on the right-hand side of the figure. The fact
that the mesentery attaching the posterior portion of the intestine to the right ven-
tral interradius appears on the right-hand side of the figure shows that the cut has
been made along the animal’s right ventral interradius, between the mesentery and
the right ventral radius. The radius which extends along the median’ axis of the
figure is therefore the left dorsal, while the right dorsal and right ventral are seen
on the left-hand side, and the left ventral and ventral on the right-hand side of the
figure (compare Fig. 20).
No. 19.] ECHINODERMS OF CONNECTICUT. 11g

teeth’, situated in the five radii. There are also five groups of
slender, sensory papillae surrounding the opening.

Respiratory Trees.*— The anterior end of the cloaca leads
forward into a broad sac, which divides into a pair of very thin-
walled tubes, the so-called respiratory trees. These are profusely
branched (Plate XXX), and extend forward nearly to the
anterior end of the body. Their very numerous broad-lobed rami-
fications (which are made too slender in the figure) expose a
vast amount of surface to the ccelomic fluids.

The musculature described above enables the cloaca to be
widely opened and filled with the external sea water. By closing
the cloacal aperture this water is forced up into the respiratory
trees under considerable pressure. In this way pure water is
supplied to the branches of the respiratory trees, and because of
the pressure a portion of the water is forced through the walls
of the branches and enters the ccelom. This cavity is thus con-
stantly filled with water, and the body walls kept tense and firm.

Such a continuous supply is necessary to replace the loss
which constantly occurs by diffusion through the tentacles and
tube-feet during the active movements of the animal.

By constantly pumping the water in and out of the cloaca the
body receives a constant supply of pure water, bringing in the
oxygen necessary for life, and carrying out the waste formed in
the metabolic processes.

When the animal is disturbed and contracts its body violently,
at the same time withdrawing its tentacles, the water in the
respiratory trees is driven out of the cloacal aperture with such
force that it forms a jet which may be ejected for a considerable
distance.

In Synapta the respiratory trees are wanting. Instead, there
are numerous ciliated funnels attached to the left dorsal mesentery
which probably have an excretory function.

Water-vascular System. t— The ring canal at the base of the
tentacles (Plate XXX) connects with radial canals which ex-
tend to the posterior end of the body between the two bands of

*By injecting colored starch paste through the cloaca, the respiratory trees
may be made to show all their branches with great distinctness.

+ It is possible to inject the water-vascular system through one of the Polian
vesicles with a colored fluid, such as Prussian blue solution. By this method the
radial canals with their branches may be rendered quite conspicuous.
120 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.

longitudinal muscles in each of the five radii. Connected with
the ring canal is the madreporic canal, which, strangely enough,
ends in a madreporic plate situated in the midst of the coelomic
cavity, as shown in Plate XXX. The water of this cavity is thus
used for the supply of the water-vascular system. Connected
with the ring canal are the large Polian vesicles, which vary in
number in different individuals from one to two, or even three.
When three are present, one of them is usually quite rudimentary.
They contain a reserve supply of fluid.

Scattered all over the internal surface of the body are the
slender ampullze connected with the tube-feet, or pedicels.

 

Fic. 21. Thyone brvareus. One of the
oral tentacles, showing the profusion of
branches.

Both the very numerous pedicels, which occur in the inter-
radial areas as well as in the radii, and the large, branched ten-
tacles are connected with the radial canals of the water-vascular
No. 19.] ECHINODERMS OF CONNECTICUT. 121

system. Both oral tentacles (Fig. 21) and pedicels are pro-
vided with muscular ampulle, which receive the fluid when the
pedicel or tentacle is contracted, as in the starfish.

In Synapta, in which pedicels are wanting, the water-vascular
system is very rudimentary, and no radial canals occur, the ten-
tacles being connected with the ring canal.

Musculature.— Paired bands of powerful longitudinal mus-
cles extend the length of the body in each of the five radii, while
transverse, or circular, muscles extend between the adjacent
radii. In all except Synapta the circular muscles are interrupted
at the radii.

Attached to the calcareous ring are powerful retractor mus-
cles by means of which the crown of tentacles, and in fact the
whole anterior part of the body, can be completely withdrawn.
They are connected with the five pairs of longitudinal muscles well
back toward the middle of the body (Plate XXX). In some
specimens these retractors are split for the greater portion of
their length into pairs, corresponding with those of the longi-
tudinal muscles, but in other individuals the two parts of each
muscle are firmly united.

The musculature of the cloaca is described above.

Body Walls.— In this species the walls of the body are'so
thick, tough and leathery that calcareous plates are wanting
except at the anterior and posterior ends of the body. In all
our other holothurians, however, characteristic plates are found
in all parts of the walls. These plates, as well as those that are
found in the tentacles and pedicels, are described in detail in
the descriptions of the different species, for they are in each
species of such characteristic form that they furnish the most
reliable means of recognizing specific differences.

Nervous System.— The quick and vigorous response which
the animal makes to various stimuli indicates a highly sensitive
nervous system,

In its morphological structure, however, the nervous system,
with its nerve ring and radial nerves, is closely similar to that
described for the starfish.

Reproductive Organs.— The sexes are separate. The sexual
gland is attached to the dorsal mesentery, and consists of a brush-
like structure, composed of numerous slender filaments all con-
122 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.

verging to a central tube, the genital duct. In reality these
filaments are in two clusters, one on each side of the mesentery,
but are commonly so closely interwoven as to appear as a single
cluster, as represented in Plate XXX. The genital duct passes
forward as a slender canal in the dorsal interradius. It opens to
the exterior in the mid-dorsal line between the bases of the dorsal
tentacles. A small papilla marks the opening of this duct in the
males.

HABITS AND FOOD

The holothurians are usually very sluggish in their move-
ments, although they respond suddenly and vigorously to various
stimuli. Our native species live largely in the mud or sand
between tides or on the sea bottom, moving slowly from place
to place as conditions of food or other circumstance may require.

In the worm-like Synapta, locomotion is accomplished by the
contractions of tentacles and body walls, while the other species
are provided with very numerous pedicels or tube-feet by means
of which they can creep about.

The species of Synapta live with the posterior end buried
deeply in the sand or mud. In our other holothurians, however,
the cloacal opening is connected with the respiratory apparatus.
Hence in these species the body is usually bent into a U-shape
with both ends near the surface of the sand or mud in which the
animals live.

Thyone.—The habits of the common Thyone and its response
to stimuli have recently been studied and described by Pearse.*
Very little is known regarding the natural history of Thyone
unisemita or Thyone scabra, for of these species very few speci-
mens have ever been seen alive.

Living, active individuals of the common Thyone kept in an
aquarium are most interesting creatures to watch. The delicately
branched, purple oral tentacles (Plate XXXI) are constantly
being alternately stretched out and withdrawn, the finer branches
gliding over the materials on which the body is resting. If
imbedded in mud or sand the tentacles spread out widely explor-
ing the surface in all directions. By this means they come in

* Biological Bulletin, 1908,
No. 19.] ECHINODERMS OF CONNECTICUT. 123

contact with any particles of organic substance or small organ-
isms which may be present. Such materials may then be grasped
by one of the tentacles, which is then withdrawn into the mouth,
and the adhering particles collected are scraped off to serve as
food. The tentacle is then thrust out for further exploration.
In such a manner quantities of mud containing more or less nutri-
tive substance pass into the alimentary canal.

When living in sand, however, the animal is able to select the
food materials and reject most of the particles of sand. Even
when sand particles are conveyed into the mouth they are often
brought out again when the tentacle returns in search of more
food. The tentacles take their turn in conveying the food, and
as a rule only a single tentacle enters the mouth at one time.
Another tentacle may bring its catch near the mouth and wait
for the first tentacle to be withdrawn before entering. An exam-
ination of the stomach contents shows the food to consist of
protozoans, small worms, crustacea and other animals, together
with diatoms, unicellular and filamentous alge and fragments
of other plants and animals.

The respiratory movements involve the whole body, the body
walls expanding and contracting as the water is taken in and
expelled from the cloacal opening. The discharged water often
forms a jet of some force.

In its natural position, the common Thyone lies with the
cloacal aperture widely opened and slightly elevated above the
surface of the sand or mud. Through this opening water is alter-
nately pumped into the cloaca and the respiratory trees and
forcibly expelled. This act of respiration often occurs with a
fairly definite rhythm, at intervals varying under different con-
ditions from 15 seconds to more than a minute. The anterior
end of the animal may also lie at the surface of the mud, with
the main portion of the U-shaped body concealed beneath the
surface. From time to time the animal buries also the anterior
end and remains for hours with only the tip of the cloaca pro-
jecting. If disturbed, there is a sudden jet of water forced from
the cloaca, and the end of the body is withdrawn beneath the
surface. Even a shadow falling upon the sensory papille sur-
rounding the cloacal opening is sufficient to cause this reaction.

If placed upon the surface of the sand the animals may either
124 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.

crawl about or bury themselves. They do not bore their way
into the sand by means of the tentacles and anterior end of
the body, as is described below for Synapta, but lie with the
ventral side upon the surface of the sand, and, by alternately con-
tracting and extending their bodies, push the sand aside and
gradually sink beneath the surface. The pedicels of the ventral
side of the body aid in pushing aside the particles of sand and
drawing the body down.

Cucumaria.— According to observations of Grave* at Beau-
fort, North Carolina, Cucumaria pulcherrima likewise lives in a
U-shaped tube near the surface of the mud near low-water
mark. The individuals of this species even when very young
show a remarkable sensitiveness to stimuli caused by vibrations,
and quickly withdraw the tentacles at the slightest disturbance.
Specimens reared from the free-swimming stage, however, and
kept in the laboratory for two or more years lose the irritability
characteristic of newly caught individuals, so that even when
removed from the aquarium with such force as to tear off many
of the tube-feet they may fail to draw in the tentacles.

When feeding, they extend the branched tentacles to half the
length of the body and gather up the diatoms and other organic
matter from the surface of the mud, as described for Thyone.
In cold weather they cease feeding and remain for long periods
of time with the tentacles withdrawn.

Synapta— The common Synapta secures its food in the
same way as Thyone. : :

In life the tentacles are almost constantly in action, reaching
out in all directions to explore surrounding objects, the digits,
or slender branches of the tentacles, being thrust out and curled
up incessantly. They secure the food and serve in burrowing.
In making the burrow, as described by Clark,} the animal bores
vertically down into the sand with the oral end foremost. The
tentacles are used to remove the particles of sand in front.

“ Synaptas burrow into the sand head first, and almost always
go straight downward for some distance, but when once com-
pletely buried, they turn in any direction up or down or on the

* Tentacle Reflex of a Holothurian, Cucumaria pulcherrima. Johns Hopkins Univ.

Circulars, No. 5, pp. 24-27, 1905.
+ Bull. U. S. Fish Commission, page 25, 1899.
No. 19.] ECHINODERMS OF CONNECTICUT, 125

horizontal plane. They can and do turn in their burrows, but
as a rule they make new tubes when they come to the surface.
They are seldom still, and the old idea that they remained in the
tube they have formed with their tentacles just above the surface
is scarcely true. Sometimes they assume that position, but sel-
dom remain so very long. They rarely leave their burrows and
come out on the surface of the sand, and I doubt if they ever do
so under normal conditions.

“ Passage through the sand is chiefly accomplished by means
of contractions and extensions of the body, but is materially
assisted by the tentacles. With the latter, which are almost con-
tinually in motion, the sand is loosened and the grains more or
less separated. By the contraction of the longitudinal muscles
the rear of the body is brought up nearer to the head, and then
the circular muscles contract and extend the body again. It is
prevented from slipping back by the anchors, which are elevated
by the contraction of the circular muscles and hold against the
sand. Since the contraction begins next to the rear end and
moves forward, the head end is pushed onward, the anchors
there lying flat in the skin.

“This process of alternate contractions of the two sets of
muscles is very obvious to an observer, and takes place very
continuously, though not rapidly. In this way a Synapta can
move through the sand from 2 to 3 centimeters a minute, and an
inherens of average size can get entirely out of sight in 5 or 6
minutes. One of the most remarkable provisions for the use
of the anchors in locomotion is their much greater abundance and
their considerably greater length in the posterior part of the body.
The use of this is clear when one realizes how the rear of the
body acts as the resisting base against which the muscles work in
pushing the anterior end forward.”

AUTOTOMY

Both Thyone and Synapta often exhibit the habit of self-
mutilation or autotomy when subjected to very unfavorable con-
ditions or strong stimuli. Such reactions, however, occur in
very different ways in the two genera. Merely placing a Synapta
in a jar of clean sea water without sufficient sand to enable it
126 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.

to bury itself will lead in a short time to violent contractions of
the posterior end of the body, resulting in the spasmodic contrac-
tion of the circular muscles at certain points with such violence
as to divide the body into two or more parts. The anterior part
may continue to cut off successive pieces until only a small frag-
ment of the anterior end of the body remains. This consists
of the tentacles, calcareous ring, nerve ring, and circular canal
of the water-vascular system, yet this fragment can under favor-
able conditions restore the normal proportions of the body.

The posterior fragments, severed from the nerve ring, may
become much constricted but do not suffer further fragmenta-
tion. Such parts are unable to regenerate the whole body.

In Thyone, the mutilation consists in such powerful contrac-
tions of the body muscles as to cause the rupture of the body
walls and longitudinal muscles immediately behind the calcareous
ring. This results in the ejection of the nerve ring, circular canal
of the water-vascular system, and a portion of the alimentary
canal, together with the whole crown of tentacles. Pearse*
describes a series of experiments to determine the conditions
under which such autotomy occurs. Various chemical stimuli and
foul water are the most effective agents in producing it. Such
mutilation as occurs in Thyone is doubtless entirely pathological
and probably causes the death of the animal in nearly all cases.
Pearse makes the statement, however, that regeneration of the
lost parts may ultimately occur.

REGENERATION

In their regenerative processes some of the holothurians
exhibit powers far beyond those of any other animals of such a
high degree of specialization. When disturbed, certain species
contract their bodies with such violence as to force out the greater
portion of their viscera, including not only the cloaca and res-
piratory apparatus, but also nearly the whole of the alimentary
canal. Under favorable conditions the normal body is restored.
While none of our own species have either this habit or its com-
pensating regenerative faculty, they are able to restore their
normal proportions after very considerable mutilation,

* Biol. Bulletin, vol. xviii, pp. 42-49, 1909.
'

No. 19.] ECHINODERMS OF CONNECTICUT. 127

The following interesting observations by Clark,* show the
ability of the common Synapta to regenerate missing parts.

“A number of experiments were made to test the tenacity of
life and the possibility of regeration in synaptas, and the results
show that ixherens is not a very sensitive animal. If an individ-
ual is cut in two the anterior end will live and grow as well
apparently as any normal specimen, but the posterior end will
only live for a few hours, or perhaps a day. So far as I could
see, the only reason for its death was its inability to take in
food; and I am inclined to think that if food could be provided
the posterior half would live as well as the anterior. It seemed
to make no difference whether the bisection occurred near to
the head or far from it; the head always lived, and in the course
of two weeks would show perceptible signs of growth. All that
seemed to be necessary was the mouth and'a small part of the
digestive tract. That it was not the tentacles which were essen- —
tial was shown by the fact that synaptas lived all right without
them. Two or more tentacles were cut from a number of syn-
aptas — in two cases every one being removed — yet they all lived
and burrowed in the sand with more or less ease; and not only
did they live, but regeneration began at once, so that in two
weeks the new tentacles were large enough to bear a digit on
each side. At first I thought the nerve ring was the essential
part, but that seems to be doubtful, for the nerve ring was care-
fully and completely severed in a synapta without apparently
causing any inconvenience. In other specimens it was cut in two
or even three places, but with the same result. In no case were
any serious effects shown, and the animals lived and burrowed
in the sand with apparently as much ease as ever. I made no
microscopical examination to show whether the nerve ends re-
united or not, but the cuts apparently healed in a short time.
The most striking fact was that with the cutting of the nerve
ring there was not the least evidence of any lack of codrdination
in the movements of the tentacles, nor of the muscles of the
body.”

* Bull. U. S, Fish Commission, 1899.
' 128 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull

REPRODUCTION AND DEVELOPMENT

In the holothurians, as in the other groups of echinoderms,
the sexes are usually separate. Most species of Synapta, how-
ever, are hermaphroditic, the sexual glands forming both eggs
and spermatozoa, which mature at different periods.

The eggs of our common species are beautifully transparent,
and have a very symmetrical type of cleavage, but are not so
easy to fertilize artificially as are those of the starfish or sea-
urchin.

Although three of the species inhabiting Long Island Sound
are found in great abundance in certain localities, very little is
known regarding their development. The absence of such
knowledge seems the more remarkable when we consider the fact
that the eggs of all three species are matured in summer, when
the opportunities for investigating problems in marine biology
are most favorable.

Grave* has been successful in rearing the free-swimming
‘larve of Cucumaria pulcherrima from the fertilized eggs. He
has also observed the transformations to the adult form and
has even been able to keep the young holothurians alive in the
laboratory for two or three years. This has been accomplished
by furnishing the animals with an abundant supply of diatoms
and other minute organisms growing at the surface of a layer
of sand. The method consists in introducing into the aquarium
a small quantity of the surface sand which has been dredged from
the ocean bottom and allowed to stand in a jar of sea water for
several days. The surface will then .be found to be covered
with a film of diatoms. The aquarium with the larve to be
reared, after receiving a small quantity of this diatom culture,
is covered and placed before a window where it will be well
lighted but not exposed to the direct rays of the sun. The
diatoms grow, and furnish an abundant supply of the natural

food of the animals, and at the same time keep up a constant
supply of oxygen. The water may be changed every few weeks
to replace the salts used by the diatoms and echinoderms.t

As in other groups, the eggs of the holothurians in which the
development is known, give rise to free-swimming embryos, which

* Johns Hopkins Univ. Circulars, No. 5, pp. 24-27, 1905.

+ C. Grave. A Method of Rearing Marine Larve. Science, vol, xv, pp. 579-580,
1902.
alae
No. 19.] ECHINODERMS OF CONNECTICUT. 129

are at first somewhat similar to those of the starfish, and are
termed auricularig. In the later stages, the embryos of many
species become barrel-shaped.

After swimming and feeding at the surface for several weeks
‘the embryo settles to the bottom and transforms itself into a
young holothurian.

In a few species from other parts of the world, the young
develop within the body cavity of the parent.

KEY TO SPECIES

The class Holothuroidea is conveniently divided into two
orders, based on the characters of the water-vascular system and
the distribution of pedicels: — (1) the Actinopoda, in which
the radial canals of the water-vascular system are well developed
and supply the oral tentacles, and (2) the Paractinopoda, in
which the radial canals and pedicels are absent, the oral tenta-
cles being supplied from the circumoral canal. The first order
includes our species of Cucumaria and Thyone, and the second
order includes the two species of Synapta.

The following key will serve to distinguish our native species:

1. Pedicels present; body not very slender..............-.- 2
Pedicels wanting ; body slender and worm-like............ 5

2. Pedicels scattered over the whole body...........-.----- 3
Pedicels mainly limited to the five ambulacral regions; body
WHILISH. cm ove ipsa arene doe Cucumaria pulcherrima

3. Ventral ambulacral area conspicuously demarcated by a dis-
tinct border free from pedicels; color white, yellowish
white, or flesh-color...............5. Thyone unisemita

Ventral ambulacral area not conspicuously demarcated ;
pedicels very numerous all over body; color brown or
blgGk: aoc naar a rece se redisaivas Coleen semis weal anes 4

4. Body tapering posteriorly, but not attenuated; pedicels del-

icate ; few calcareous plates in body wall. Thyone briareus
Body attenuated posteriorly; pedicels and body wall rough
from closely crowded calcareous plates...Thyone scabra

5. Color white or yellowish; the five radial plates of calcareous
ring perforated for passage of nerve..Synapta inhzrens

Color reddish or pink; radial plates of calcareous ring
notched in anterior border............. Synapta roseola

9
130 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.

Cucumaria pulcherrima (Ayres)
Plate XXXII, figs. 2 to 6.

   

Teor a a

Fic. 22. Cucumaria pulcherrima. Specimen preserved in alcohol,
showing ambulacral areas and arrangement of tube-feet (pedicels).
Five times natural size.

This pretty little holothurian, formerly known as Pentamera
pulcherrima, has been collected at many localities from’ Vineyard
Sound to South Carolina, although very few specimens have been
taken from their natural habitat. Living animals are rarely
found even in systematic dredging. In certain localities, how-
ever, considerable numbers are washed up on the beach after
hard storms. Most of the specimens in collections have been
secured in this way. The species has been dredged at least once
in Vineyard Sound, although in very thorough dredgings in the
same region during several subsequent years no specimens were
secured. In the very locality where large numbers of individuals
have been washed up on the beach during the winter, systematic
search by means of dredgings on the bottoms off shore the
following summer were without success. It has been found on
the beach after severe storms at several localities on the Con-
necticut shore. Among the seaweed thrown up by the waves on
the rocky points both east and west of New Haven, the species
has been found repeatedly during the colder months of the year.

In the harbor of Beaufort, North Carolina, the species occurs
near low-water mark in muddy localities where there is a growth
No. 19.] ECHINODERMS OF CONNECTICUT. 131

of eelgrass. Grave has reared the larve to the adult form, and
has succeeded in keeping the young holothurians to the age of
two or three years by the methods described on page 128.

Color white or pale yellowish. Size usually about 1 inch long
and a half-inch in diameter; rarely reaching a length of 2 inches.

In such specimens as are washed up by the waves the body
is oval, sometimes tapering towards one end; with a distinct
curve, the two ends being bent dorsally, with the result that the
length of the body measured along the ventral surface is much
greater than if measured along the dorsal surface.

There are ten much branched tentacles, of which the two
ventral are much smaller than the others, as in Thyone. In the
specimens found on the beach they are usually fully retracted
into the body, as shown in Plate XXXII, figs. 2 to 6.

The tube-feet, or pedicels, are rather stout, and are strictly
limited to the five ambulacral regions, or radii (Fig. 22).

The cloacal opening is surrounded by five small groups of
pedicels which are stiffened with thickly placed calcareous
deposits (Fig. 23). Imbedded in the body walls in all parts of

 

Fic. 23. Cucumaria pulcherrima. Outlines of calcareous plates. The
upper left-hand plate is from a tentacle; the three lower left-hand plates
are from the pedicels; all the others are from: the body wall. (X 300.)
132 CONNECTICUT GEOL, AND NAT. HIST. SURVEY. pBull.

the body are closely crowded calcareous deposits of characteristic
form: (Fig. 23). They greatly increase the firmness of the
integument. Some of these deposits are quite symmetrical, while
others are very irregular. The most typical shape is that of a
table in form of a parallelogram, perforated by four oval holes,
and surmounted by a spire consisting of two rods with a few
sharp points at the apex (Fig. 23). Others are rectangular, with
six holes, and a small spire. Still others have eight, ten, or
occasionally more holes. Some are considerably elongated, and,
when unusually slender, have one or two small holes in each
extremity. The vast majority have graceful, curved or wavy
outlines, and are remarkably symmetrical. At the posterior end
of the body the tables become densely packed together, and are
of much larger size than those found elsewhere. Near the
cloaca the spire of the tables becomes much reduced, the deposits
assuming the form of large perforated plates. ;

The cloacal opening is supported by a ring of crowded cal-
careous plates of large size, but quite irregular in shape
(Fig. 24).

In the pedicels the calcareous deposits are slender tables, and
near the extremity are reduced to supporting rods with perforated
ends. The tip of each pedicel has a terminal perforated plate
(Fig. 24).

 

Fic. 24. Cucumaria pulcherrima. Outlines of calcareous plates. A,
from cloaca; B, terminal disks of pedicels. (X 150.)

In the tentacles there are a few small plates of very irregular
outline, with an occasional one of much larger size.
 

 

 

 

 

PLATE XXXI. Common Thyone, 7hyone briareus.
No. 19.] ECHINODERMS OF CONNECTICUT. 133

Thyone briareus (Leseur)
Common Thyone

Plate XXIX, fig. 5; Plates XXX and XXXI.

This species is distributed from Vineyard Sound to the Gulf
of Mexico, occurring from near low-water mark to a depth of
ten fathoms on both sandy and muddy bottoms. In certain local-
ities it is very abundant, while in seemingly equally favorable
situations it does not occur. It is commonly found buried in soft
mud in shallow water, often with its body bent into a U-shape,
with both extremities at the surface of the mud. In this position
its much branched, purplish tentacles stretch out on the surface
of the mud in search of the fine particles of organic matter which
constitute its food. The posterior end, with the cloacal aperture
usually widely opened, likewise reaches the surface of the mud
and alternately sucks in and discharges the water used in res-
piration. The species is often found at the bottom of streams
and creeks where the water is decidedly brackish.

The color of the body is purplish, brownish, or blackish, the
pedicels lighter, often with a reddish cast, and the terminal disks
yellowish. ;

The body when mature may become six or even nine inches
in length when fully extended, most individuals, however, being
about three or four inches long and an inch or more in diameter.
In shape, the animal is largest in its middle portions, being some-
what narrower anteriorly, and tapering decidedly toward the
posterior end (Plate XXXI); but the whole body may become
regularly oval or much rounded in certain states of contraction.

The mouth, situated in the center of the anterior end, is sur-
rounded by a crown of ten tentacles, of which the two ventral
are much smaller than the others. All are profusely branched,
as shown in Fig. 21. The bases of these tentacles and their
larger branches are stiffened by the development of numerous

 

 

EXPLANATION OF PLatE XXXI. Thyone briareus.

Fig. 1. Portion of one of the oral tentacles, showing the terminal finger-
like processes. Much enlarged.

Fig. 2. Large specimen with oral tentacles expanded, and pedicels fully
extended. Natural size.

Fig. 3. Preserved specimen with oral tentacles partially contracted.
Natural size.
134 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. {Bull.

perforated calcareous plates, and somewhat similar plates occur
more sparingly in the smaller branches. They are either rod-like
or broad, and are commonly perforated by six or more holes
(Fig. 25).

The body walls, especially in mature specimens, are without
calcareous deposits in the greater part of the body. At both
extremities, however, there are numerous peculiar calcareous
deposits known as “tables.” These tables are more or less
nearly square or rectangular, and are perforated by about eight
rounded holes. At right angles to this plate is the so-called spire,
made up of about four short rods ending in teeth and connected
by one or two cross processes (Fig. 25).

 

Fic. 25. Outlines of calcareous plates of Thyone briareus. A,
terminal plate of pedicel; B, supporting plates of pedicels; C,
plates from tentacles; D, plates (tables) from body-walls.

The slender pedicels, or tube-feet, are very numerous, and
are scattered irregularly all over the body. Occasionally they
appear to be arranged in five very broad longitudinal bands,
although such bands are not distinctly separated from each other.
The pedicels of the ventral surface are broader than those of the
dorsal side of the body, the latter commonly tapering to a point.
In the extremity of the pedicel is a terminal circular plate (Fig.
25), perforated by many minute holes. In the walls of the ped-
icels are other perforated plates, some of which are modified to
form supporting plates, while others are provided with a short
spire (Fig. 25).

The cloacal opening has five groups of small papilla, and a
calcareous ring with the five tooth-like processes known as the
anal teeth.
No. 19.] ECHINODERMS OF CONNECTICUT. 135

The calcareous ring at the base of the tentacles is very broad,
and the radial plates have rather slender prolongations. ,

The internal anatomy of this species is described in detail on
pages 116 to 122, and is illustrated on Plate XXX. The habits
and reactions té stimuli have recently been studied by Pearse, and
are described in an interesting article in the Biological Bulletin,
Vol. XV, pp. 259-288, 1908. The sexual products mature in June.

Thyone unisemita (Stimpson)
Single-striped Thyone
Plate XXXII, fig. 1.

In the earlier writings of Ayres and Verrill this species was
placed in the genus Stereoderma, and as such appears in Verrill
and Smith’s Invertebrate Animals of Vineyard Sound. There
are few available records of the collection of this species in Long
Island Sound. The United States Fish Commission collected
twelve specimens off Watch Hill, Rhode Island, at a depth of
eleven fathoms. Six of these specimens are preserved in the
Yale University Museum. The Fish Commission likewise records
the collection of two other specimens in Long Island Sound, but
without giving the number of station or precise locality. The
species has also been dredged on sandy bottoms at various local-
ities from southern New England northward to the Banks of
Newfoundland, but has nowhere been found in abundance.

The living animals are white, flesh-colored, or yellowish white,
with orange-yellow tentacles. Most specimens are less than two
inches in length, although one individual measuring three inches
in length has been recorded.

The body is somewhat U-shaped, and narrowed at both ends.
The pedicels cover the dorsal and lateral surfaces, but on the
ventral side there is only one double row situated along the mid-
ventral line. This row is rendered the more conspicuous because
it is bordered on each side by a wide area of smooth skin, giving
the characteristic effect of a single ventral stripe.

The calcareous deposits in the body wall (Fig. 26) consist
of flattened plates, many of which are symmetrical and perforated
by, four holes. Others are larger, irregular in outline, and with
136 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.

 

°o 5
5 og
Sp 9
620 Oe ce 90. °o
eo 2
°°
fo?
> O
09
o
00
0 0 0 B e9

  

Fic. 26. Thyone unisemita. Outlines of calcareous plates. A, from
body-wall; B, madreporic plate; C, from pedicels; D, from tentacles.
(After Clark.)
numerous perforations. The madreporic plate and the charac-
teristic plates of the pedicels and tentacles are shown in Fig. 26.

Further details of the anatomy may be found in Clark’s
Report on the Echinoderms of the Woods Hole Region.

Thyone scabra Verrill
Rough-skinned Thyone
Plate XXXII, fig. 7.

This species has not as yet been recorded from Connecticut
waters. It is, however, included in this report because it has
been collected near the eastern entrance to Long Island Sound,
and is reported from Narragansett Bay. Hence its occurrence

 

 

EXPLANATION OF PLATE XXXII.

Fig. 1. Thyone unisemita. Three specimens preserved in alcohol, with
completely retracted peristome and tentacles. Slightly en-
arged.

Figs. 2-6. Cucumaria pulcherrima. Five specimens after preservation in
formalin, showing variations in shape of body and ambulacral
areas. Slightly enlarged.

Fig. 7, Thyone scabra, Preserved specimen with extended peristome,
and partially extended tentacles. Slightly tee

Fig. 8. Synapta inherens. Anterior portions of body of two individuals

; with partially contracted tentacles. Natural size.

Fig. 9. Synapta inherens. Posterior portion of body, showing two of

the five longitudinal muscular bands. Twice natural size.
XXII. Thyone, Cucumaria, and Synapta.

 
No. 19.] ECHINODERMS OF CONNECTICUT. : 137

is probable in the colder and deeper waters at the eastern end of
the Sound.

The species ranges northward to the Bay of Fundy, and has
been reported as far south as Delaware, although the record for
the last-named region may not be without question. It extends
from shallow water to a depth of more than 600 fathoms.

There are no records as to the color or general appearance
of the living animal, the species having been studied and described
from preserved specimens. When preserved in alcohol, the color
is brownish, with lighter pedicels. Nothing is known regarding
its habits.

 

Fic. 27. Thyone scabra. Outlines of cal-
careous plates. A, from tentacles; B. from
body-wall. (After Clark.)

The individuals of this species are very mitch smaller than
those of the common Thyone, rarely exceeding two inches in
length. The body is slender posteriorly and pointed at the
extremity.

The most striking characteristic of the species is the abun-
dance of the calcareous deposits in the skin. These are placed
so closely together as to cause a decided roughness over the
whole surface of the body. The deposits consist mainly of ir-
regular plates (Fig. 27), usually pierced by eight to twelve or
more holes, and provided with a rather small handle, or spire.
The spire is made up of two or three stout columns, united at
the top and crowned with small, irregular teeth.
138 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.

The plates in the pedicels are narrow and curved, with four
central perforations besides one or more holes at each end; while
those of the tentacles are rod-like, often with irregular outline,
and perforated (Fig. 27).

For other anatomical details see Clark’s Report in the Bulletin
of the U. S. Fish Commission for 1902, or Verrill’s original
description.*

Synapta inherens (O. F. Miller)
Common Synapta

Plate XXIX, figs. 3, 4; Plate XXXII, figs. 8, 9.

It was formerly thought that the common New England
Synapta represented a distinct species, to which the name Lepto-
synapta girardi was applied, and this name is used in Verrill
and Smith’s Report on the Invertebrate Animals of Vineyard
Sound. It has been shown, however, that our form is specifically
identical with the well-known European Synapta inherens. A
very complete description of the anatomy and habits of this spe-
cies has been published by Clark, in the Bulletin of the U. S.
Fish Commission for 1899.

This is a very widely distributed species, being found not only
on the Atlantic coast of the United States and along the European
shore from the Arctic Ocean to the Mediterranean Sea, but also
on the Pacific coast of North America from Alaska to Monterey
Bay and Point Loma, California. It also occurs at Bermuda.

Along the Connecticut shore it is very commonly distributed,
and occurs in a great variety of situations.

It is most frequently seen on sandy flats between tides, where
its burrows can be recognized, when the water is low, by the small
mound of sand commonly of different color from that at the
surface. In the center of this mound can be seen the small hole
in which the creature is living. This hole descends perpendic-
ularly, with a diameter of from one-fourth to three-eighths of an
inch.

Although most commonly found in clean sand, it also occurs
in muddy situations, and can even live in soft, black mud.

 

*Am. Journ. Science, ser. 3, vol. v, 1873.
No. 19.] ECHINODERMS OF CONNECTICUT. 139

Furthermore it is often found in coarse gravel, and sometimes
beneath large stones. And finally, it occurs not only between
tides, where the mouths of its burrows may be exposed to the air
for an hour or more, but also below low-water mark, extending
to a depth of over 100 fathoms. When found in sand between
tides its body remains deep in the wet sand beneath the surface,
where there is an abundance of water for respiration.

Its ability of adapting itself to such a wide range in the
character of its environment, probably accounts for its very wide
geographical distribution.

The body is long, slender, cylindrical and worm-like, and cap-
able of great extension. It is so delicate and fragile that com-
plete specimens are difficult to preserve intact. Its length is
often 4 to 6 or more inches, with a diameter of 14 to 3% of an
inch.

The color of the body is white, often with a distinct tinge of
yellow and occasionally of very pale red. The rosy hue of some
specimens is due to minute particles of red pigment in the integ-
ument, but the reddish color is never so distinct as in the succeed-
ing species. The integument is thin and delicate, and often so
translucent that the five bands of longitudinal muscles, which are
opaque white in color, and certain of the internal organs, can be
distinguished in the living animal. This is particularly true of
the intestine, which is filled with sand, and of the reproductive
organs when the sexual products are mature.

There are twelve tentacles (Plate XXIX, fig. 3), with char-
acteristic branches. Each tentacle commonly consists of a main
stalk and five or seven pairs of branches (Plate XXIX, fig. 4),
though there are occasionally only three pairs. The branches
are tubular or finger-like projections, and are termed digits.
Each tentacle has a number of peculiar sense organs on the inner
surface near the base. Calcareous deposits, consisting of oval
or knobbed plates or rods, occur in the tentacles.

The most characteristic features of the species of this genus,
however, are the very remarkable calcareous deposits found in the
body walls. These consist of structures resembling miniature
anchors, each of which is connected with a perforated plate of
characteristic design (Fig. 28). These occur in all parts of the
140 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.

body,* but are smaller anteriorly than elsewhere, increasing grad-
ually in size toward the posterior end of the body.

The anchor has a narrow shank, with rather short arms; on
the outer side of. the flukes are several minute spines. The
shank is narrowed near the point where it joins the short, slightly
curved stock.

The plate, or table, on which the anchor rests has seven sym-
metrically placed perforations, with serrated margins, followed
by a transverse row of three oval perforations, with smooth mar-
gins, and several small, smooth holes toward the posterior border.
Forming an arch above the three oval perforations is a short

 

Fic. 28. Synapta inherens. Calcareous plates. A, portion of
calcareous ring; B, anchors and plates from body-wall; C, plates
from tentacles; D, plates from longitudinal muscles. (A, C, and
D after Clark.)

transverse process, raised above the level of the plate by a pair of
supports at each end (Fig. 28).

The calcareous ring is broad, the plates being without pro-
jections on either side. The radial plates are perforated near the
center for the passage of the radial nerves. This character alone
will serve to distinguish this species from the following. Of the
internal anatomy, it is necessary to mention only the large, spiral
intestine, which extends the whole length of the body, the single

* These anchors and plates make most beautiful microscopic objects, They can be
prepared by soaking a piece of the body wall in a solution of caustic potash until it
is thoroughly softened, when it can be washed in water, and the deposits mounted
as desired.
No. 19.] ECHINODERMS OF CONNECTICUT. 141

Polian vesicle, the terminal cloaca, and the very slender filaments
of the gonads. Respiratory trees are absent, and, as the body
is without pedicels, the radial vessels of the water-vascular
system are wanting in the adult.

In Long Island Sound the animals are sexually mature in the
late spring and early summer. The eggs appear fully ripe during
the last week in May on the sand flats of Savin Rock. Attempts
at artificial fertilization have not been successful.

When removed from its burrow, the animal is very restless,
and, if it is roughly handled, or if the water becomes stale, the
posterior portion of the body is likely to break into numerous
pieces.

This species secures its food by extending its tentacles upon
the surface of the sand at the mouth of its burrow, and grasping
with the digits such particles of organic substances and sand: as
may be selected. In this way vast quantities of sand are devoured,
the digestible substances contained among the particles or adher-
ing to them being absorbed. The intestine is always filled with
sand or mud, which may be of such a color as to affect the color-
ation of the posterior part of the body.

The presence of the anchors in the integument enables the
animals to cling closely to objects with which they may come in
contact. It thus often happens that, when specimens of Synapta
are collected with specimens of other animals, and placed in a
jar of water, the whole collection may become entangled into an
inextricable mass.

Specimens may be kept alive in an aquarium with a deep layer
of clean sand in the bottom, for some weeks, if there is a con-
stant supply of pure sea water.

Synapta roseola (Verrill)
Pink Synapta
Plate XXIX, figs. 1, 2.

This beautiful little holothurian resembles the preceding spe-
cies closely, but is easily distinguished by the granules of red
pigment scattered so thickly over the body as to give it a delicate
rose-pink color. It has, moreover, certain anatomical peculiar-
ities by which it can be recognized, even after the color has dis-
142 CONNECTICUT GEOL. AND NAT. HIST, SURVEY. {Bull.

appeared from preserved specimens. Individuals of this species
are usually smaller than those of S. inherens, fully mature spec-
imens rarely measuring much over 4 inches in length and 4
inch in diameter.

The body is slender and cylindrical, with a crown of delicate
tentacles at the anterior end. It is, as in the preceding species,
very fragile. The animal is prone to break up the posterior
portion of its body into many pieces when removed from its
burrows. The color is pink, pale red, or sometimes fairly deep
red, occasionally with a ting@ of yellow. The color is mainly
due to deep red granules of pigment scattered over the integument,
particularly in the anterior portion of the body. When con-
tracted, the color naturally becomes more intense than when
extended. When sexually mature the filamentous gonads are
conspicuous through the delicate body walls.

This species ranges from Massachusetts Bay to Long Island
Sound, and is very abundant at Bermuda. Although it is locally
distributed, it is very common in certain places.

The sexual products are ripe in summer, the genital glands
at that time filling the anterior portions of the body, and plainly
visible through the translucent body walls. Occasionally the
eggs may be artificially fertilized and reared to the stage of free-
swimming larvee, but for some unknown reason the majority of
attempts at artificial fertilization have been unsuccessful.

Its habits are somewhat different from those of Synapta
inherens, for this species is more commonly found in coarse
gravel and beneath and between stones. It sometimes occurs in
sand. In certain localities specimens may be most easily obtained
by turning over the stones beneath which the animals live. It
occurs both between tides and below low-water mark.

The anatomical peculiarities which distinguish this species
from Synapta inherens are fully discussed by Clark.*

Each of the twelve tentacles has usually but two or three
pairs of digits (Plate XXIX, figs. 1 and 2). The calcareous
deposits in the tentacles are very irregular, much branched, or
perforated, while those in the longitudinal muscles are irregular
or incomplete rings (Fig. 29).

*The Synaptas of N. E. Coast. Bull. U. S. Fish Commission, 1899.
No. 19.] | ECHINODERMS OF CONNECTICUT. 143

The anchors and plates which are found in all parts of the
body wall are very similar to those in S. imherens, but both

A

c

 

ASS
yw 2G

Fic. 29. Synapta roseola. Calcareous plates.
A, portion of calcareous ring; B, anchor and
plate from body-wall; C, plates from tentacles ;
D, plates from longitudinal muscles. (After
Clark.)

anchors and plates have a tendency to be more slender (Fig. 29).
It is the calcareous ring, however, which furnishes the most pre-
cise criterion of distinction, for in this species all the plates
are rather narrow, and the radial plates have a notch on the
anterior border for the passage of the radial nerve (Fig. 29),
instead of the perforation found in S. inherens (Fig. 28).

Both species occur on the sand flats at Savin Rock, near New
Haven, in great abundance.

Clark, in his extensive Monograph on the Apodous Holo-
thurians (Smithsonian Contributions to Knowledge, vol. XXXV,
1907), has revised the old genus Synapta and now places our
two native species, inherens and roseola, in Verrill’s genus
Leptosynapta. Although his reasons for doing this appear to be
perfectly valid, it has been thought best to retain the long pena
generic name in the present work.
BIBLIOGRAPHY

Of the vast amount of literature relating to the Echinoderms,
the following list contains only a few of the books and papers
which treat of the subject in such a comprehensive manner as to
be useful to the general reader, or which have special reference
to the species found in Connecticut waters. Of the latter only
such have been selected as are referred to in the text of the
article. In order to make the list as brief as possible, many
papers of great importance to the professional zodlogist have been
purposely omitted.

The articles are arranged in alphabetical order, with the date
immediately following the name of the author for convenience of
reference.

Agassiz, A. 1872-1874.

Revision of the Echini. Jil. Cat. Mus. Comp. Zodl., No. 7.

A most important work on the structure and relationships
of the echinoids. ~

Agassiz, A. 1877.

North American Starfishes. Mem. Mus. Comp. Zodl., Vol.
-v, No. I.

A beautifully illustrated monograph on the external anatomy
of our native starfishes.

Agassiz, Elizabeth C. and Alexander. 1865.

Seaside Studies in Natural History. Marine Animals of
Massachusetts Bay. Radiates. Boston. Houghton, Mif-
flin and Company.

This little book contains a popular account of some of our
most interesting marine invertebrates, including many of
the echinoderms.

Arnold, Augusta Foote. 1go1.

The Sea Beach at Ebb Tide. New York City. The Century
Company.

A well illustrated and interestingly written guide to the study
of the marine invertebrates and plants.
‘ ,

ECHINODERMS OF CONNECTICUT. 145

Ayres, W. O. 1851-1854.

Notices of Holothuriz and other Echinoderms. Proc. Bost.
Soc. Nat. Hist., Vol iv.

Although written more than a half-century ago, the descrip-
tions of the natural history of many of our native species
are as interesting as any that have been published since.

Bather, Z A., assisted by Gregory, J. W., and Goodrich, E. C.
1900.

The Echinoderma. Lankester’s Treatise on Zodlogy, Pt. iii.

Ong of the most valuable works on the general anatomy,
relationships, and natural history of the group.

Brooks, W. K.

Handbook of Invertebrate Zodlogy.

A well-known guide to the laboratory study of invertebrates.
Clark, H. L. 1899.

The Synaptas of the New England Coast. Bull. U. S. Fish
Commission.

A clearly written and well illustrated report on our two
native species of Synapta.

Clark, H. L. igor. .

Synopsis of North American Invertebrates. XV. The Holo-
thuroidea. American Naturalist, Vol. xxxv, 1901.

A brief account of the anatomical peculiarities of the holo-
thurians, followed by analytical keys to the genera and
species found on both the Atlantic and Pacific coasts of
North America.

Clark, H. L. 1904.

The Echinoderms of the Woods Hole Region. Bull. U. S.
Fish Commission for 1902.

Concise systematic descriptions of nearly all the species of
echinoderms found in the waters of southern New Eng-
land. Each species is illustrated by excellent photo-
graphs, most of which were made from living animals.

Fewkes, J. W. 1887.
On the Development of the Calcareous Plates of Amphiura.
\ Bull. Mus. Comp. Zodl., Vol. xiii, No. 4.

An important contribution to the embryology of the ophiu-

rans.

10
146 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull.

Fisher, W. K. 1rgtt.

Asteroidea of the North Pacific and adjacent waters. Part
1, Phanerozonia and Spinulosa. Bull. 76, U. S. National
Museum.

An extensive monograph, containing detailed anatomical
descriptions and a critical discussion of the relationships
of the starfishes of the North Pacific. Illustrated by 122
quarto plates.

Ludwig, H. 1892.
Die Seewalzen. Bronn’s Tierreich, Band ii.
A classic monograph on the holothurians.
Lyman, T. 1865.

Ophiuride and Astrophytide. Jil. Cat. Mus. Comp. Zéol.,
No. 1.

Contains a systematic account of the American ophiurans.

Lyman, T. 1882.

Report on the Ophiuroidea. Challenger Reports, Vol. v,
Pt. 14.

A systematic treatise on the ophiurans of the world.

Mac Bride, E. W. 1906.

Echinodermata. Cambridge Natural History.

One of the most important general accounts of the echino-
derms ever written. Contains many excellent illustrations
of the anatomical structures and developmental stages of
the various groups.

Mead, A. D. Igo.

The Natural History of the Starfish. Bull. U. S. Fish Com-
mission for 1899, Vol. xix. ,

The most interesting account of the natural history of the
common starfish.

Preyer, W. 1887.

Ueber die Bewegungen der Seesterne. Mitt. aus der Zoél.
Station au Neapel, Band 7.

A classical paper on the movements of starfish.

Romanes, G. J. 1885.

Jellyfish, Starfish, and Sea-urchins. London. International
Scientific Series.

A most entertaining popular account of the natural history
of these groups of animals,
No. 19.] ECHINODERMS OF CONNECTICUT. 147

Sladen, W. P. 1880.
Report on the Asteroidea. Challenger Reports, Vols. xxx
and xxxi.
A monograph of the starfishes of the world.
Theel, H. 1886.
Report on the Holothurioidea. Challenger Reports, Vol. xiv.
A monograph of the holothurians of the world.
von Uexkull, J. 1909.
Umwelt und Innenwelt der Tiere. Berlin.

A series of most interesting stories about the habits of rep-‘

resentatives of various groups of invertebrates, including
the classes of echinoderms, with an account of their
behavior under a great variety of natural and artificial
conditions.

Verrill, A. E., and Smith, S. I. 1874.

Report on the Invertebrate Animals of Vineyard Sound and
Adjacent Waters. Report of Commissioner of Fish and
Fisheries, Vol. i, for 1871-2. Washington.

The most comprehensive report on the marine invertebrates
of southern New England that has yet been published.
Although some new species have been discovered since
the work appeared, and the scientific names of some of the
species have been revised, it is still the standard work on
the subject. The accounts of the natural history of the
very numerous species included in the report are most
interestingly written.

Verrill, A. E. 1895.

Distribution of the Echinoderms of Northeastern America.
Am, Journ. Sci., Vol. xlix.

Discusses the geographical and bathymetrical distribution of
the various species.

Verrill, A. E. 1899.

North American Ophiuroidea. Trans. Conn. Acad., Vol. x.

Revision of the synonymy and distribution of many of the
ophiurans of the east coast of North ‘America and the
West Indies,

/
INDEX

Abnormalities, starfish, 44.

Actinopoda, 129.

Age of sexual maturity, starfish, 42

Alimentary canal, holothurian, ne
key-hole urchin, 95.
sand-dollar, 97.
starfish, 25.

Amphioplus abditus, 14, 67, 75, 76,

79, 82.
description, 83.
geographical distribution, 82.
habits, 82

Amphioplus macilentus, 14, 79, 84.
description,
geographical distribution, 84.

Amphipholis squamata, 14, 69, 76,

77, 79, 81.
description, 82.
geographical distribution, 81.

Amphiura squamata, 81.

Amphiura elegans, 81.

Antedon dentatus, 13.

Arbacia punctulata, 14, 85, 88, 80,

102, 103, 104, 106, 107, 109.
description, 107.
geographical distribution, 107.

Arm plates, ophiuran, 7o.

Artificial fertilization, 50.

Asterias, 33.

Asterias compta, 63, 64.

Asterias forbesi, 13, 19, 21, 22, 4I,

43,59.
description, 60.
geographical distribution, 59.

Asterias rubens, 61.

Asterias tenera, 14, 50, 63.
breeding habits, 52.
description, 64.
geographical distribution, 64.

Asterias vulgaris, 13, 25, 44, 48, 52,

59, 60, 61, 64.
anatomy, 25. .
breeding habits, 52.
description, 62.
geographical distribution, 61.

Asteroidea, 13, 19.
alimentary canal, 25.
behavior, 29.
body walls, 21.

branchiz, 21.

circulatory system, 27.

damage to oysters and other
mollusks, 33.

development, 52.

external structure, 20.

food, 29.

habits, 28.

internal structure, 25.

key to species, 58.

locomotion, 19.

method of feeding, 30.

migration, 43.

mouth, 22.

movements, 24.

natural enemies, 32.

nervous system, 27.

ossicles, 24.

pedicellariz, 21.

rate of growth, 40, 41.

regeneration, 45.

reproduction, 48.

reproductive system, 28, 49.

tube-feet, 22.

variation in number and ar-
rangement of rays, 43.

water-vascular system, 26.

Auricularia, 129,
Autotomy, holothurian, 125.
ophiuran, 75.
starfish, 45.

Behavior, starfish, 29.

Bibliography, 144.

Bipinnaria, 53.

Blastula, sea-urchin, 100.

Blood starfish, 58, 65.

Body walls, holothurian, 121.

starfish, 21.

Branchiz, starfish, 21.

Brachiolaria, 53.

Breeding habits, Asterias forbesi, 49.
Asterias tenera, §2.
Asterias vulgaris, 52.
Henricia, 52.

Breeding season, starfish, 49.

Calcareous ring, holothurian, 118.
Circulatory system, starfish, 27.
150

Clam, damage to, caused by starfish,

39, 57.

Classification of Echinoderms, 13.
Cleavage of egg, sea-urchin, ror.
Cloaca, holothurian, 118.
Clypeastroidea, 92, 104.

anatomy, 92,

development, 104.

locomotion, 94.
Common starfish, 59.

description, 59.

development, 52.

See also Asteroidea.
Common Synapta, 138.
Common Thyone, 133.
Cribrella sanguinolenta, 65.
Crinoidea, 13.
Cucumaria pulcherrima, 15, 124, 129,

130.

description, 131.

food, 124.

geographical distribution, 130.

Daisy Brittle-star, 80.
Damage to oysters and other mol-
lusks by starfishes, 33.
Development, blood starfish, 58.
clypeastroids, 104.
common starfish, 52.
echinoids, 100.
holothurians, 128,
key-hole urchin, 104.
northern starfish, 58.
ophiurans, 77.
sand-dollar, ro4.
slender-armed starfish, 58.
Digestive system, key-hole urchin,

95.
ophiuran, 73.
sand-dollar, 97.
sea-urchin, &o.
starfish, 25.
Disk-urchin, anatomy, 92.

Echinarachnius parma, 14, 16, 92, 93,
95, 106, IIo.
description, r11.
geographical distribution, 110.
habits, 110,
Echinodermata, characters, 12.
eee ores economic importance,
16.
literature, 144.
methods of preservation, 17.
scientific interest in, 16.
Echinoidea, 14, 85.
development, 100.
digestive system, 89.

CONNECTICUT GEOL. AND NAT. HIST. SURVEY.

[Bull.

food, 99.
habits, 97.
internal anatomy, 89, 94.
key to species, 106
locomotion, 97.
natural enemies, 99.
nervous system, QI.
reproduction, 100.
reproductive system, 91.
structure, 85.
water-vascular system, 90.
Eggs, number produced by echi-
noids, 100.
Eleutherozoa, 13.
Embryo, ophiuran, 77.
sea-urchin, 102.
starfish, 53.

Fertilization, ophiuran, 77.
sea-urchin, 100.
starfish, 49.

Food, disk-urchin, 96, 99.
echinoid, 99.
holothurian, 122.
ophiuran, 75.
sea-urchin, 90, 99.
starfish, 29.

Forcipulata, 59.

Green ophiuran, 79.
Green sea-urchin, 108.

Habits, Cucumaria, 124.

echinoids, 97.

holothurians, 122.

ophiurans, 73.

starfish, 28.

Synapta, 124.

Thyone, 122.
Henricia, breeding habits, 33, 52.
aa sanguinolenta, 13, 14, 59,

S.
description, 66.
geographical distribution, 65.
Holothuroidea, 15, 114.
alimentary canal, 116.
autotomy, 125.
body walls, rar.
calcareous ring, 118.
cloaca, 118.
development, 128.
food, 122.
habits, 122.
internal anatomy, 116.
key to species, 129.
musculature, 121.
nervous system, I2I,
regeneration, 126.
No. 19.] ECHINODERMS

reproduction, 128.
reproductive organs, 121.
respiratory trees, 119.
structure, I14.
water-vascular system, I19.

Internal anatomy, Thyone, 116.
sea-urchin, 89
Internal structure of arms, ophi-
uran, 71.
Internal structure, starfish, 25.

Key-hole urchin, 112.
internal anatomy, 95.

Key to species, Asteroidea, 58.
Echinoidea, 1
Holothuroidea, 129,
Ophiuroidea, 79.

Larve, methods of rearing, 128.
Leptosynapta girardii, 138.
Leptosynapta inherens, 138, 143.
Leptosynapta roseola, 141, 143.
Literature on Echinoderms, 144.
Locomotion, disk-urchin, 94, 97.

echinoid, 97.

ophiuran, 735

starfish, 19.
Losses caused by starfish, 34, 39.

Madreporic plate, echinoid, 88.
holothurian, 120.
ophiuran, 70.
starfish, 20.
Mellita pentapora, 14, 16, 85, 95,
105, 106, 112.
description, 112.
geographical distribution, 113.
Mellita quinquiesperforata, 112.
Mellita testudinata, 112.
Metamorphosis, starfish, 54.
key-hole urchin, 105.
sea-urchin, 103.
Migration, starfish, 43.
Mouth, disk-urchin, 95.
sea-urchin, 86.
ophiuran, 68.
starfish, 22.
Musculature, holothurian, 121.
Mutilation, starfish, 46, 47.

Natural enemies, echinoid, 99.
starfish, 32.

Nervous system, holothurian, 121.
sea-urchin, 91.
starfish, 27.

Northern starfish, 58, 61.
development, 58,

OF CONNECTICUT.

151

Ophiopholis aculeata, 14, 67, 68, 78,
79, 80.
description, 81.
geographical distribution, 80.
Ophiura brevispina, 13, 14, 71, 78,

79.

description, 80.

geographical distribution, 79.
Ophiura brevispina, var. olivacea,

79-
Ophiura olivacea, 79.
Ophiuroidea, 14.
arm plates, 70.
characteristics of, 67.
development, 77.
digestive organs, 73.
disk, 69
fertilization, 77.
food, 75.
genital burse, 76.
habits, 73.
internal structure of arms, 71.
key to species, 79.
locomotion, 73.
methods of feeding, 76.
regeneration, 75.
reproduction, 76.
structure, 68,
tube-feet, 71.
viscera, 73.
Ossicles, starfish, 24.
Oysters, damage caused by starfish,
33, 57-

Paractinopoda, 129.
Pedicellariz, starfish, 21, 62.
Pelmatozoa, 13.
Pentamera pulcherrima, 130.
Pink Synapta, 141.
Pluteus, echinoid, 102, 103.
ophiuran, 78.
Purple sea-urchin, 107.
Rate of growth, starfish, 4o.
Regeneration, holothurians, 126.
ophiurans, 75.
starfish, 45.
Synapta, 127.

Regularia, 91, 92, 106.

Reproduction, echinoid, roo.
holothurians, 128.
ophiuran, 76,

starfish, 48.
Reproductive organs, holothurian,
121.

sea-urchin, 9I.
starfish, 28.
Respiratory trees, holothurian, 119.
152

Rough-skinned Thyone, 136.

Sand-dollar, 96, r1o.
internal anatomy, 96.
Sea-urchins. See Echinoidea.
Single-striped Thyone, 135.
Slender-armed starfish, 58, 63.
development, 58.
Spatangoidea, 106
Spinulosa, 59.
Starfish, abnormalities, 44.
age at sexual maturity, 42, 48.
artificial fertilization, 50.
breeding season, 49.
damage to oysters and other
mollusks, 33, 57.
effect of mutilation, 47.
fertilization, 49.
habits of young, 56.
losses caused by, 34.
method of feeding, 30.
methods of controlling injuries
by, 35, 37, 39 56, 58.
species of, 58.

See also Asteroidea.
Strongylocentrotus drébachiensts,
14, 85, 86, 89, 106, 108.

description, 109.
geographical distribution, 108.
habits, 109.

Synapta, 15, 124, 127.
habits and food, 124, 138, 141.
regeneration, 127.

Synapta inherens, 15, 129, 138, 140,

142,

description, 139.
geographical distribution, 138.
habits, 124, 138, 141.

Synapta roseola, 15, 129, I4I.
description, 141.

CONNECTICUT GEOL. AND NAT. HIST. SURVEY.

{Bull.

geographical distribution, 142.
habits, 142,

Thyone, 15, 116.
alimentary canal, 116.
body walls, 121.
calcareous ring, 118.
cloaca, 118,
food, 123.
habits, 122. 5
internal anatomy, 116.
musculature, 121.
nervous system, 121.
reproductive organs, 121.
respiratory tree, 119.
water-vascular system, II9.
Thyone briareus, 15, 114, 117, 120,
129, 133.
description, 133.
geographical distribution, 133.
Thyone ae 15, I14, 122, 129,
136.
description, 137.
geographical distribution, 136.
Thyone untsemita, 15, 114, 122, 120,
135.
description, 135.
geographical distribution, 135.
Tube-feet, ophiuran, 71.
starfish, 22.

"Variation in number and arrange-
ment of rays, starfish, 43.

Water-vascular system, holothurian,
119.
ophiuran, 73.
sea-urchin, go.
starfish, 26.

Zygophiure, 79.