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 14. ANIMAL PHYSIOLOGY. By J. Cleland, M.D., F.R.S., Professor 
 
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ELEMENTS OF ZOOLOGY. 
 

 V* 
 
 ELEMENTS^ Z^LOGY 
 
 AND SCIENCE CLASSES. 
 
 BV 
 
 M. HARBISON, 
 
 / f~ 
 HEAD MASTER, MODEL SCHOOL, NEWTOWNARDS. 
 
 NEW YOKK: 
 G. P. PUTNAM'S SONS, 
 
 FOURTH AVENUE AND TWENTY-THIRD STREET. 
 

 . r' 
 
PEEFACE. 
 
 THE present Work is confined to a description of the 
 Sub-kingdoms and Classes of Animals. As it is desirable 
 that students should have some knowledge of Animal 
 Physiology before entering on the study of Zoology, less 
 space is devoted to the Vertebrata than is usual in Zoolo- 
 gical works. The higher animals are described first, as 
 it is believed that this arrangement is more suitable for 
 beginners. 
 
 The Author has tried to adapt his language to the 
 capacity of the students who attend classes in connection 
 with the Department of Science and Art, and the more 
 advanced pupils in schools. Technical terms have been 
 freely used, but their derivation is always given, and full 
 explanations will be found in the Glossary. Questions 
 for Examination are added to each Chapter, which will, 
 it is hoped, be found useful to both teachers and pupils. 
 
 Materials have been drawn from a great variety of 
 sources, but the Author especially acknowledges his 
 obligations to the works of PROFESSOR HUXLEY, DR. 
 NICHOLSON, DR. HAUGHTON, and MR. GOSSE. The 
 Illustrations, of which there are sixty-two, have been 
 mainly derived from GERVAIS' Elements de Zoologie. 
 
 MODEL SCHOOL, 
 NEWTOWNARDS, November, 187 S* 
 
 526 ti 
 
CONTENTS. 
 
 INTRODUCTION. PAGE 
 
 Definition Differences between Organic and Inorganic 
 
 Bodies Classification, 9 
 
 CHAPTER I. 
 
 GENERAL CHARACTERS OF THE SUB-KINGDOMS. 
 
 Vertebrata Annulosa Aunuloida Mollusca Mollus- 
 
 coida Ccelenterata Protozoa Questions, ... 14 
 
 CHAPTER, II. 
 
 VERTEBRATA. 
 
 Mammalia Aves Reptilia Amphibia Pisces Ques- 
 tions, . 2G 
 
 CHAPTER III. 
 ANNULOSA AND ANNULOIDA. 
 
 Arthropoda Insecta Myriapoda Arachnida Crustacea 
 Anarthropoda Annelida Cho3tognatha Annu- 
 loida Scolecida Rotif era Turbellaria Trematoda 
 Toeniada Nematoidea Acanthocephala Gordiacea 
 Echinodermata Questions, ..... 58 
 
 CHAPTER IV. 
 
 MOLLUSCA AND MOLLUSCOIDA. 
 
 Cephalopoda Pteropoda Gasteropoda Lamellibran- 
 chiata Brachiopoda Tunicata or Ascidioida Poly- 
 zoa Questions, ... i .... 95 
 
g CONTENTS. 
 
 CHAPTER V. 
 
 CCELENTERATA AND PROTOZOA. pAQB 
 
 Actinozoa Sea Anemone Coral Coral Reefs Cteno- 
 pliora Hy dr ozoa Hydra Corynid se Tubularia 
 Sertularidae Lucernaridae Medusae Infusoria Rhi- 
 zopoda Amoeba Foraminifera Radiolaria Poly- 
 cystinse Spongida Gregarinida Questions, , , 124 
 
 GLOSSARY, , t 9 t t f t t , 159 
 
ZOOLOGY. 
 
 INTRODUCTION. 
 
 NATURAL HISTORY, strictly speaking, includes the study 
 of all natural objects, whether animate or inanimate. It 
 consists of two great divisions : -first, that which treats 
 of inorganig or dead bodies ; second, that which deals with 
 organic or living substances. The sciences which treat of 
 inorganic bodies are termed Mineralogy and Geology, 
 while that which deals with the properties common to 
 organic beings (plants and animals) is termed Biology 
 (Gr. bios, life; logos, a discourse). This science com- 
 prises Botany (Gr. botane, a plant), which treats of the 
 properties of plants, and Zoology (Gr. zoon, an animal; 
 logos, a discourse), which investigates the nature and 
 habits of animals. In the popular use of the term, 
 Natural History is often synonymous with Zoology. 
 
 The most important differences between organic and 
 inorganic bodies are : 
 
 1. Inorganic bodies are either indefinite in shape (amor- 
 plious), or assume regular forms called " crystals," which 
 are bounded by plane surfaces and straight lines. Organic 
 bodies are generally definite in shape, and are bounded by 
 curved lines and rounded surfaces. 
 
 Inorganic bodies increase in size by the addition of 
 similar particles to the outside. Organic bodies grow 
 by the receiving and assimilation of matter into the 
 interior. 
 
10 ZOOLOGY. 
 
 2. Characteristic Differences between Plants and Ani- 
 mals. Both, plants and animals are organic bodies. They 
 both possess life, and are able to propagate their kind. 
 Although it v is generally easy to distinguish between 
 plants and animals, yet there is a border land in which 
 it is difficult to determine where the one kingdom ends 
 and the other begins. The following are the most char- 
 acteristic differences of the two kingdoms ; but, as will 
 be seen, the distinctions can scarcely be looked upon as 
 universal. 
 
 3. Chemical Composition. Most of the characteristic 
 substances found in plants, such as starch, sugar, &c., are 
 composed of three elements carbon, oxygen, and hydro- 
 gen. On the other hand, albumen and fibrine, so abun- 
 dantly met with in animal tissues, are composed of four 
 elements carbon, oxygen, hydrogen, and nitrogen. This 
 distinction, however, is not universal, as compounds of 
 the three elements are met with in animals, while nitro- 
 gen is present in several vegetable products. 
 
 4. Peeling or Sensibility was selected by Linnaeus as 
 the leading characteristic of the animal kingdom. In 
 such animals as possess a nervous system, the distinction 
 is worthy of the position assigned to it by the great 
 naturalist. But when it is remembered that two primary 
 groups of animals, the Protozoa and the Ccelenterata, are 
 utterly devoid of a nervous system, the characteristic 
 fails to be universally applicable. 
 
 5. Locomotion. This characteristic, which is so marked 
 in the higher groups, also fails when we reach the more 
 lowly organisms. Many of these, such as the sponges, 
 corals, and corallines, are as much confined to a particular 
 spot as plants are. On the other hand, many minute 
 aquatic plants, such as the Diatomacese, are able to move 
 about with great rapidity. 
 
 6. Organs of Digestion. The possession of a re- 
 ceptacle, in which to deposit and digest their food, is a 
 feature broadly distinctive of the animal kingdom. Many 
 of the Protozoa, however, are destitute of any permanent 
 
INTRODUCTION. 11 
 
 alimentary apparatus, and require, when they take in 
 nutriment, to extemporize a cavity foi its reception. 
 
 7. The Nature of the Pood is the most widely applicable 
 of the distinctive features of the two kingdoms. This 
 distinction may be briefly stated thus : Plants are able 
 to convert inorganic matter into organic; but no animal, 
 so far as our present knowledge extends, is able to subsist 
 upon inorganic substances. The food of plants consists 
 principally of carbonic acid, water, and ammonia, together 
 with small quantities of various salts. These substances 
 are derived partly from the air, and partly from the earth. 
 The carbon of the carbonic acid is retained by them, and 
 the oxygen set free. Animals, on the other hand, deprive 
 the air of its oxygen, and give off carbonic acid. Animals 
 are able to subsist only on the complex organisms pre- 
 pared for them by plants, the food of these being of a 
 more simple character. " Plants are the great manu- 
 facturers in nature, animals the great consumers." (Dr. 
 Nicholson.) 
 
 These distinctions, however, are not universally true. 
 On the one hand, several of the fungi are as dependent 
 on organic food as animals are; while, it is probable, that 
 some microscopic animals may be able to subsist on 
 inorganic compounds. 
 
 8. Classification. Various systems of classification have 
 been adopted by different naturalists. Lamarck divided 
 the animal kingdom into two great divisions, the Verte- 
 brata and Invertebrata. The first of these is still re- 
 tained as a primary division, but the second contained 
 such a heterogeneous assemblage that further division 
 became necessary. Accordingly, Cuvier, another French 
 naturalist, subdivided the Invertebrata into Mollusca, 
 Articulata, and Radiata. As the new world of animal 
 life revealed by the microscope could not be assigned to 
 any of these groups, it became necessary to form a 
 separate division, to which the name of Protozoa has 
 been given. 
 
 Careful examination showed that Cuvier's Badiata 
 
12 ZOOLOGY. 
 
 included animals with and without a nervous system, 
 and differing widely in other important structures. This 
 group has, therefore, been broken up, and its members 
 assigned to various sub-kingdoms. 
 
 Following closely the arrangement proposed by Pro- 
 fessor Huxley, we venture to divide the Animal King- 
 dom into seven primary groups or sub-kingdoms. 
 
 The following table gives the great divisions of the 
 Animal Kingdom, together with the classes into which 
 they have been subdivided : 
 
 SUB-KINGDOM I. Vertebrata. 
 
 CLASS 1. Mammalia. Ex., Man, Horse, Deer. 
 
 2. Aves (Birds). Ex., Hawk, Crow, Parrot, 
 Goose. 
 
 3. Reptilia (Reptiles). Ex., Crocodile, Turtle, 
 Lizard, Snake. 
 
 4. Amphibia. Ex., Frog, Toad, Newt, Sala- 
 mander. 
 
 , 5. Pisces (Fishes). Ex., Herring, Salmon, Shark, 
 Kay. 
 
 SUB-KINGDOM II Annulosa. 
 DIVISION I. Arthropoda. 
 
 - CLASS 1. Insecta. Ex., House-Fly, Beetle, Bee, But- 
 terfly. 
 
 2. Myriapoda. Ex., Centipede, Millipede. 
 
 3. Arachnida. Ex., Scorpion, Spider, Mite. 
 
 ,, 4. Crustacea. Ex., Lobster, Crab, Shrimp, Bar- 
 nacle. 
 
 DIVISION II. Anarthropoda, 
 
 CLASS 1. Chsetognatha. Ex., Sagitta. 
 
 2. Annelida. Ex., Earth-worm, Leech, Lob* 
 worm, Serpulse. 
 
INTRODUCTION* - ,. . - \3 
 
 SUB-KINGDOM III. Annuloida. 
 
 CLASS 1. Scolecida. Ex., Tape-worm, Fluke, Wheel- 
 Animalcule. 
 
 2. Echinodermata. Ex., Star-fish, Sea-Urchin, 
 Encrinite. 
 
 SUB-KINGDOM IV. Mollusca. 
 
 CLASS 1. Cephalopoda. Ex., Nautilus, Cuttle-fish, 
 
 Squid. 
 
 2. Pteropoda. Ex., Clio Borealis, Dentalium. 
 3. Gasteropoda. Ex., Snail, Limpet, Whelk. 
 4. Lamellibranchiata. Ex., Mussel, Cockle, 
 
 Scallop, Oyster. 
 
 SUB-KINGDOM V. Molluscoida. 
 
 CLASS 1. Brachiopoda. Ex., Terebratula, Lingula. 
 2. Tunicata or Ascidioida. Ex., Sea-Squirt 
 3. Polyzoa. Ex., Flustra or Sea-Mat. 
 
 SUB-KINGDOM VI. Coelenterata. 
 
 CLASS 1. Actinozoa. Ex., Coral, Sea- Anemone, Sea- 
 Pen. 
 2. Hydrozoa. Ex., Hydra, Sea-Fir, Sea- Jelly, 
 
 
 SUB-KINGDOM VII. Protozoa. 
 
 CLASS 1. Infusoria. Ex., Paramcecmm, Vorticella. 
 2. Rhizopoda. Ex., Sponge, Amoeba, Foramini- 
 
 fera. 
 3. Gregarinida. Ex., Gregarina. 
 
Z06LQGY, 
 
 CHAPTER I. 
 
 CHARACTERS OF THE SUB-KINGDOMS, 
 
 SUB-KINGDOM I. Vertebrata. 
 
 9. The first primary division of animals is termed Verte- 
 brata. It is so called on account of the almost universal 
 presence of a vertebral column or backbone. The 
 skeleton or hard parts are internal ; some groups, how- 
 ever, such as the Crocodiles and Tortoises, have also an 
 external skeleton. This skeleton consists of the bony 
 case, called the cranium or skull, and a series of pieces, 
 which are united together, and form the axis, termed the 
 vertebral column. Attached to the vertebrae there is 
 generally a number of bony arches, termed ribs, which 
 are united by cartilages to the sternum or breastbone. 
 Then there are the bones that support the limbs, 
 which are greatly modified in the various groups. 
 
 Zr-~ 
 
 PIG. l. 
 
 A, Transverse section of an invertebrate animal ; B, Section of a vertebrate : 
 b, wall of the body ; a, alimentary canal ; h, haemal or blood system ; n, principal 
 nervous system; n', sympathetic nervous system of vertebra ta; c, notochord. 
 It will be seen, that, in the Vertebrata, the main mass of the nervous system is 
 dorsal (Lat dorsum, the back), and ventral (Lat. venter, the belly) iu the 
 Iiivertebrata, while the blood system is ventral iu the Vertebrata, and dorsaj 
 in the Invertebrata, 
 
CHARACTERS OF THE SUB-KINGDOMS. 15 
 
 To the various 'parts of this skeleton the muscles are 
 attached. 
 
 The nervous system of the Vertebrata is very character- 
 istic. An invertebrate animal consists only of a single 
 tube, which contains the nervous system as well as the 
 organs of circulation and digestion. If a vertebrate 
 animal, however, be cut in two, it will be seen to consist 
 of two tubes, an upper and a lower. The upper tube is 
 formed by two bony arches which proceed from the 
 centre or body of the vertebra or joint of the backbone. 
 These are termed the neural arches (Or. neuron, a 
 nerve), and form the canal in which the spinal cord is 
 enclosed. This cord is connected with the brain, which 
 is contained in the skull. These form the main mass 
 of the nervous system. 
 
 The lower and much larger tube contains the alimen- 
 tary canal and other digestive organs, the organs of cir- 
 culation, and what is called the " sympathetic " nervous 
 system which seems to correspond with the nervous 
 system of the Invertebrata. 
 
 Some Yertebrata, as the serpents, &c., are destitute of 
 limbs ; and some, as the whales, possess only one pair. 
 Generally, however, there are two pairs present, and no 
 vertebrate animal has more than four limbs. 
 
 They have all a complete alimentary or intestinal canal 
 provided with two openings, terminating respectively in 
 a mouth and anus or vent. This canal is always com- 
 pletely shut off from, the general cavity of the body. 
 There is generally an oesophagus or gullet, and a stomach 
 with large and small intestines. 
 
 The heart is formed of a variable number of cavities, 
 called auricles and ventricles. Mammalia, or animals 
 which nourish their young with a fluid called milk, and 
 birds, have two auricles and two ventricles ; reptiles and 
 amphibia (frogs, toads, &c.), two auricles and one ven- 
 tricle ; fishes, one auricle and one ventricle. 
 
 The blood is red, with the exception of one species of 
 fish, the lancelet, which has colourless blood. The colour 
 
16 ZOOLOGY. 
 
 is due to the globules called corpuscles (Lat. corpus, a 
 body ; cle, little), and not to the fluid in which they are 
 suspended, this being colourless. It circulates to all parts 
 of the body, in a system of close vessels, called veins and 
 arteries. The arteries convey the blood from the heart, 
 the veins carry it back. 
 
 There are always special respiratory or breathing 
 organs for the purification of the blood. In mammals, 
 birds, and reptiles, the oxygen required for this purpose 
 is obtained directly from the atmosphere. Their breath- 
 ing organs are called lungs. Fishes breathe by gills, and 
 obtain the oxygen from the air dissolved in water. The 
 amphibia breathe by gills when immature, and by lungs 
 in the adult state. In all cases, the organs of respiration 
 are connected with the commencement of the digestive 
 tube. 
 
 In all the vertebrates the male and female organs are 
 found in distinct individuals. 
 
 DIVISIONS OP THE VEKTEBRATA. 
 
 10. This sub-kingdom is divided into five classes : 
 
 1. Mammalia (warm-blooded quadrupeds which suckle 
 their young). 
 
 2. Aves (Birds). 
 
 3. Reptilia (Reptiles). 
 
 4. Amphibia (Frogs, Toads, &c.) ; and 
 
 5. Pisces (Fishes). 
 
 11. The Amphibia and Pisces agree in possessing gills 
 during either the whole or a part of life j the embryo is 
 destitute of the membranous sac, termed the amnion 
 (Gr. amnos, a lamb), and of the structure called the 
 allantois (Gr. alias, a sausage) ; the red blood-corpuscles 
 are oval in shape, and contain a nucleus. These two 
 classes, according to Professor Huxley, form the 
 division Ichthyopsida, (Gr. ichthus, a fish ; opsis, appear- 
 ance). 
 
 12. The Eeptilia and Aves have also nucleated red blood- 
 
CHARACTERS OF THE SUB-KINGDOMS. 17 
 
 corpuscles; the embryo is provided with amnion and 
 allantois ; gills are never present during any period of 
 life ; the skull is joined to the vertebral column by a 
 single condyle (Gr. condulos, a knuckle) on the occipital 
 bone; each half of the lower jaw consists of several pieces; 
 the lower jaw is joined to the skull by a bone called the 
 quadrate (Lat. quadra, a square) bone. These two classes 
 form the division Sauropsida (Gr. sauros, a lizard). 
 
 13. The Mammalia form a distinct section. They agree 
 with the Sauropsida in being destitute of gills, and in 
 possessing an amnion and allantois; but differ from them 
 in having circular red blood-corpuscles, without any 
 nucleus, in possessing glands for the secretion of milk 
 (mammary glands), and in being generally covered with 
 hair. There are two condyles on the occipital bone, each 
 half of the lower jaw consists of a single piece, and is 
 united directly with the skull, and not to a quadrate 
 bone. 
 
 SUB-KINGDOM II. Annulosa. 
 
 14. This sub-kingdom, which is also sometimes termed 
 Articulata, comprises those animals that consist of a num- 
 ber of rings or segments, arranged behind one another 
 in a straight line. There is no skeleton properly so called, 
 but the hardness of the external covering of most of them 
 compensates for the absence of the internal framework 
 found in the Vertebrata. This hardness is sometimes 
 due to lime, which, in crabs, lobsters, &c. (Crustacea) 
 forms a hard external crust. 
 
 Sometimes the cuticle is hardened by a chemical sub- 
 stance termed chitine (Gr. chiton, a tunic), allied to horn, 
 the skin, in such cases, somewhat resembling a tanned 
 hide. This is the nature of the covering in the insects, 
 centipedes, &c. To these hardened rings the muscles are 
 attached. 
 
 There is always a nervous system which is situated 
 below the alimentary canal. It generally consists of a pair 
 15 E. B 
 
18 ZOOLOGY. 
 
 of ganglia (Gr. ganglion, a knot) placed in each ring or 
 segment, and connected by two nervous cords or commis- 
 sures (Lat. committo, to join together), which run along 
 the whole ventral surface of the body. The first or front 
 pair of ganglia, is always situated above the alimentary 
 
 FIG. 2. DIAGRAM OF AN ANNULOSE ANIMAL. 
 a, haemal or blood system; b, neural system; c, digestive system. 
 
 tube, and the nervous cords connecting this with the 
 second pair pass round the gullet, and are in consequenco 
 termed the (BSOphageal collar. The nervous system is 
 lodged in the same cavity as the digestive and circulatory 
 organs, the body walls forming a single tube (see fig. 1). 
 
 The alimentary canal has always two openings, and is 
 completely shut off from the cavity of the body. 
 
 DIVISIONS OP THE ANNULOSA. 
 
 15. The sub-kingdom Annulosa comprises two great 
 divisions the Arthropoda (Gr. arthros, a joint; podes, 
 feet), or animals with jointed limbs, and those in which 
 these appendages are absent. The latter have been termed 
 Anarthropoda (Gr. an, without). 
 
 The Arthropoda comprise : 
 
 1. Insecta (Bees, Butterflies, &c.) 
 
 2. Myriapoda (Centipedes, &c.) 
 
 3. Arachnida (Spiders, &c.); and 
 
 4. Crustacea (Crabs, Lobsters, &c.) 
 
 The principal characteristic of this group is the posses- 
 session of three or more pairs of jointed limbs composed 
 of the chitinous substance described above, These limbs 
 
CHARACTERS OP THE SUB-KINGDOMS. 19 
 
 are sometimes confined to one region of the body, and 
 sometimes distributed over all the segments of it. 
 
 The blood is a colourless fluid, containing corpuscles. 
 The blood-vessels are situated above the alimentary canal. 
 
 Respiration is performed differently in the various 
 classes. 
 
 The principal class in the division Anarthropoda is the 
 Annelida or worms, which are destitute of jointed limbs. 
 
 SUB-KINGDOM III. Annuloida. 
 
 16. The members of this sub-kingdom were formerly 
 included in the Annulosa, but have now been separated 
 from it and erected into an independent group. The 
 reasons assigned by Professor Huxley for this separation 
 are : Their bodies are not marked by definite rings or 
 segments, there is no longitudinal chain of ganglia, and 
 none of them possess limbs arranged in pairs. 
 
 Two classes have been assigned to this primary division, 
 
 1. Echinodermata (Gr. echinos, a hedgehog; derma, 
 
 skin), including sea-urchins, star-fishes, &c. ; and, 
 
 2. Scolecida (Gr. scolex, a worm), consisting princi- 
 
 pally of internal parasites. 
 
 At first sight there seems to be very little resemblance 
 between these two classes, a sea-urchin and a tape-worm 
 being as unlike one another as possible. They both, 
 however, possess what has been called the "water- vascular" 
 system, that is, "a series of canals communicating with 
 the exterior by means of apertures situated upon the 
 surface of the body, and branching out more or less 
 extensively into its substance." 
 
 SUB-KINGDOM IV. Mollusca. 
 
 17. The Mollusca (Lat. mottis, soft,) are invertebrated 
 animals whose bodies are covered by a soft skin, which 
 envelops them like a loose sac. This covering is called 
 the mantle. It secretes the shell which most of them 
 possess, and to it the muscles are attached. This shell is 
 
20 ZOOLOGY. 
 
 composed of carbonate of lime, and sometimes consists of 
 a single piece or " valve," sometimes of two valves 
 united together by a hinge. 
 
 The digestive tube is always completely separated 
 from the general cavity of the body, and is provided with 
 an anal opening. 
 
 The higher groups possess an organ situated at the 
 entrance to the alimentary canal, which is commonly called 
 the " tongue ;" but which, on account of the minute 
 flinty teeth with which it is furnished, Professor Huxley 
 has termed an odontopkore (Gr. odous, a tooth ; pkero, I 
 carry), or tooth-bearer. It works backwards and for- 
 wards on a cartilaginous cushion like a chain saw. It is 
 by means of this odontophore that the slugs and snails 
 make such havoc in our gardens. 
 
 The blood in this group is colourless. There is a dis- 
 tinct heart, with two cavities, which occupies the dorsal 
 position. The blood passes from the gills, or other 
 breathing organ, to the auricle, thence to the ventricle, 
 which propels it through the body. 
 
 The nervous system is very distinctive. It consists of 
 three pairs of ganglia united by nervous cords. One of 
 these pairs, situated in front above the oesophagus, is 
 termed the cerebral ganglia; another, which sends branches 
 to the foot, is termed the pedal ganglia; and the third. 
 
 FIG. 3. DIAGRAM OF A MOLLUSC, 
 
 a, digestive tube ; I, heart ; c, foot ; d y cerebral ganglia ; e, pedal ganglia ; 
 /, parie to-splanchnic ganglia. 
 
 which communicates with the walls of the body, as well as 
 with the digestive and reproductive organs, is termed the 
 
CHARACTERS CT THE SUfi-ffflfolfiOllS. 21 
 
 parieto-splanchnic ganglia (Gr. parietes, walls; splanchna, 
 the internal organs). 
 
 Respiration is generally effected by gills or branchiae. 
 In the land snails, and in some fresh water molluscs, 
 the breathing organ is termed a pulmonary sac. It 
 consists of an opening hollowed out on the right side 
 of the body, near the neck, and supplied with blood- 
 vessels. The blood in these animals is purified by coming 
 directly into contact with the oxygen of the atmosphere, 
 and not through the medium of water as in those that 
 breathe by gills. 
 
 18. The sub-kingdom Mollusca is divided into the fol- 
 lowing classes, viz.: 
 
 1. Cephalopoda (Gr. cephale, the head ; poda, feet). 
 
 2. Pteropoda (Gr. pteron, a wing ; poda, feet). 
 
 3. Gasteropoda (Gr. g aster, the stomach). 
 
 4. Lamellrbranchiata (Lat. * lamella, a plate ; Gr. 
 Iranchia, a gill). 
 
 SUB-KINGDOM V. Molluscoida. 
 
 19. This division is allied to the Mollusca, but its 
 characters are sufficiently distinct to entitle it to rank 
 as an independent group. 
 
 The heart, when present, is in the form of a simple tube 
 or sac, and is never separated into auricle and ventricle. 
 
 The nervous system generally consists of a single 
 ganglion. 
 
 The mouth is either surrounded with ciliated tentacles, 
 or with long arms, which have a ciliated fringe. 
 
 The alimentary tube has two openings, and is com- 
 pletely shut off from the cavity of the body. 
 
 There are three classes in this sub-kingdom : 
 
 1. Brachiopoda (Gr. brachia, arms; poda, feet). 
 
 2. Tunicata or Ascidioida (Lat. tunica, a cloak ; Gr. 
 askos, a bottle ; eidos, form). 
 
 3. Polyzoa (Gr. polus, many; zoon, an animal). 
 
22 ZOOLOGY. 
 
 SUB-KINGDOM VI. (telenterata, 
 
 20. The Coelenterata (Gr. Jcoilos, hollow ; enteron, an in- 
 testine) form a very distinct division of the animal 
 kingdom. The red and white corals, many of the coral- 
 lines, sea jellies, &c., belong to it. These were placed by 
 Cuvier, along with some other groups, in the division 
 named by him Eadiata. From their resemblance to 
 plants many of them have also been called Zoophytes. 
 (Gr. zoon, an animal ; phuton, a plant). 
 
 The body wall always consists of two layers, an outer 
 and an inner. The external covering is called the 
 ectoderm (Gr. ectos, outside ; derma, skin) ; the inner 
 lining, the endoderm (Gr. endos, within). These layers 
 have a cellular structure, and are generally furnished 
 with cilia (Lat. cilium, an eyelash), which constantly 
 vibrate. 
 
 There is a circle of tubular arms round the mouth. 
 These are called tentacles (Lat. tento, I touch), and are 
 used by the animals in seizing their prey. 
 
 The most distinctive feature in this group is the 
 digestive apparatus. In all the divisions hitherto de- 
 scribed it was seen that the digestive canal is completely 
 shut off from the body cavity, and communicates with 
 the exterior by an anus or vent. In the Cffilenterata, 
 however, the alimentary tube opens at its inner end into 
 the general cavity of the body, and communicates freely 
 with it. As there is no anal opening, the indigestible 
 portions of the food are expelled from the mouth. 
 
 Another peculiar feature of the group is the possession 
 of stinging organs in the form of "thread cells." These 
 may be examined by the microscope in the common fresh- 
 water hydra. " These cells are oval elastic sacs, contain- 
 ing a long coiled filament, barbed at its base, and serrated 
 along the edges. When fully developed the sacs are filled 
 with fluid, and the slightest touch is sufficient to cause 
 the retro version of the filament, which then projects be- 
 
CHARACTERS OP THE SUB-KINGDOMS. 23 
 
 yond the sac for a distance which is not uncommonly 
 equal to many times the length of the latter." (Huxley.) 
 These organs are doubtless used by the animals in killing 
 their prey, as well as in defence. Some of the "jelly 
 fishes' 7 have filaments large enough to penetrate the 
 human skin. 
 
 No organs of circulation or respiration are known to 
 exist. Only in one group is there any trace of a ner- 
 vous system. All of them have distinct reproductive 
 organs. 
 
 This sub-kingdom is divided into two classes : 
 
 1. Actinozoa (Gr. afais, a ray; zoon, an animal). 
 
 2. Hydrozoa (Gr. fmdra, a water serpent ; soon, an 
 animal). 
 
 SUB-KINGDOM VII. Protozoa, 
 
 21. The Protozoa (Gr. protos, first ; zoon, an animal), as 
 the name signifies, is the lowest primary division of the 
 animal kingdom. Most of the animals in this division 
 are so small that they can only be seen by a powerful 
 microscope. Some, however, as the sponges, are of large 
 size. On account of their minute size they are popularly 
 called animalcules. Until recently, they were compara- 
 tively unknown even to the scientific world. Most 
 people are still unaware of their existence. They are 
 essentially aquatic animals, and may be found abun- 
 dantly in any stagnant pond, or in water containing 
 decayed animal or vegetable matter. 
 
 The bodies of the Protozoa are composed of a substance 
 termed sarcode (Gr. sarx, flesh ; eidos, form). It is also 
 sometimes called protoplasm (Gr. protos, first ; plasso, I 
 mould.) This substance is jelly-like, and has been de- 
 scribed by some observers as resembling the white of an 
 e gg y by others it is said to be like a particle of " thin 
 glue." It is mainly composed of albumen, and is without 
 any definite structure. 
 
 Except in one group, the Infusoria, there is no perma- 
 
24 ZOOLOGY. 
 
 nent moutli nor any digestive organ whatever. No trace 
 of a nervous system has been observed. 
 
 In the Infusoria locomotion is effected by cilia, which 
 are kept perpetually in motion. The lower forms have 
 the power of extemporizing processes termed pseudopodia 
 (Or. pseudos, false ; poda, feet). These are sometimes 
 finger-like, and sometimes fine filaments resembling 
 minute threads. 
 
 This sub-kingdom has been divided into three classes : 
 
 1. Infusoria (so called because they are met with in 
 infusions of vegetable matter). 
 
 2. Rhizopoda (Or. rhiza, root ; poda, feet). 
 
 3. Gregarinida (Lat. gregarius, occurring in flocks). 
 
 QUESTIONS. L 
 
 1. Strictly speaking, what sciences are included in "Natural 
 
 History"? 
 
 2. What is the popular use of this term ? 
 
 3. What are the two great divisions of natural objects ? 
 
 4. What is Biology, and what sciences does it include? 
 
 5. Define Zoology. 
 
 G. What are the leading distinctions between organic and in- 
 organic bodies ? 
 
 7. What are the principal differences between plants and 
 
 animals ? 
 
 8. What substances do living animals and plants respectively 
 
 contribute to the atmosphere ? 
 
 9. Name the primary groups of animals, and the classes into 
 
 which they are subdivided. 
 
 10. What are the principal characters of the sub-kingdom 
 
 Vertebrata ? 
 
 11. What are the principal parts of the vertebrate skeleton ? 
 
 12. Describe the nervous system. 
 
 13. How are the brain and spinal cord protected ? 
 
 14. How does a transverse section of a vertebrate animal differ 
 
 from a similar section of an invertebrate ? 
 
 15. How many limbs have the Vertebrata, and what arc the 
 
 exceptions to this rule ? 
 
 16. How does the heart differ in the various groups ? 
 
 17. What is the nature of the blood ? 
 
 18. What are " corpuscles " ? 
 
 19. What vertebrate animal has colourless blood ? 
 
CHARACTERS OF THE SUB-KINGDOMS. 25 
 
 20. How do the breathing organs differ in the various classes ? 
 
 21. What are the primary divisions of the Vertebrata ? 
 
 22. Name the classes or subdivisions. 
 
 23. What are the points of agreement between Amphibia and 
 
 Fishes ? 
 
 24. How do Reptilia and Birds resemble one another ? 
 
 25. What are the leading distinctions of the Mammalia ? 
 
 26. Define the sub-kingdom Anmdosa. 
 
 27. How does the skeleton differ from that of the vertebrates ? 
 
 28. What is "chitine"? 
 
 29. Describe the nervous system. 
 
 30. What are " ganglia"? 
 
 31. What are " commissures " ? 
 
 32. Name the primary divisions of the Anmdosa. 
 
 33. Name the sub-divisions, and give examples. 
 
 34. What is the nature of the blood in the Arthropoda ? 
 
 35. Why have the Anmdoida been separated from the Annulosa ? 
 
 36. What are the principal characteristics of this sub-kingdom ? 
 
 37. What is the " water vascular system " ? 
 
 38. What classes are included in the Annuloida ? 
 
 39. State why these classes have been placed in the same sub- 
 
 kingdom. 
 
 40. Why are the Mollusca so called ? 
 
 41. What classes are included in this sub-kingdom? 
 
 42. Describe the digestive apparatus in the Mollusca. 
 
 43. Describe the circulatory organs. 
 
 44. Describe the nervous system. 
 
 45. How is respiration effected in this group ? 
 
 46. What is an ' ' odontophore " ? 
 
 47. Define the Molluscoida. 
 
 48. What classes are contained in this sub-kingdom ? 
 
 49. Why have they been separated from the Mollusca ? 
 
 50. Define the Cozlenterata, and give the derivation of the word. 
 
 51. What is the peculiarity of the digestive apparatus in this 
 
 sub-kingdom ? 
 
 52. What classes does it embrace ? 
 
 53. What is the derivation of Protozoa? 
 
 54. Name the classes included in this sub-kingdom. 
 
 55. What is the general character of these groups of animals ? 
 
 56. What is "sarcode"? 
 
 57. What are "cilia"? 
 
 58. What are "pseudopodia"? 
 
26 ZOOLOGY. 
 
 CHAPTEB, II. 
 
 VERTEBRATA. . 
 CLASS I, Mammalia. 
 
 22. The highest class of vertebrate animals is termed 
 Mammalia (Lat. mamma, the breast). It is so called 
 because the young, being brought forth in a state more or 
 less helpless, are, for a time, nourished by a fluid called 
 milk, secreted by a set of glands termed "mammary 
 glands." 
 
 The following are the most important characteristics 
 of the Mammalia : 
 
 They are covered with hair; the skull is united to the 
 vertebral column by two occipital condyles; each half 
 of the lower jaw consists of a single piece; the lower jaw 
 is joined directly with the skull, and not to the quad- 
 rate bone; the heart has four cavities two auricles and 
 two ventricles; the red blood-corpuscles are circular, and 
 non-nucleated; the blood is hot; respiration is always 
 effected by lungs; the diaphragm completely separates 
 the cavities of the thorax and abdomen; the hemispheres 
 of the brain are united by a corpus callosum ; the embryo 
 is provided with an amnion and an allantois ; the young 
 are nourished by milk, secreted by mammary glands. 
 
 23. Skeleton. The skull in the Mammalia is united to 
 the vertebral column by two condyles on the occipital 
 bone. There are two corresponding "facets" on the 
 atlas, or upper joint of the vertebral column. Each half 
 of the lower jaw consists of only a single piece, and is 
 articulated directly with the skull, and not to the quad- 
 rate bone, as in birds and reptiles. 
 
 24. The divisions of the vertebral column usually 
 recognized are : 
 
 1 . The cervical (Lat. cervix, the neck) region or neck. 
 
VERTEBRATA MAMMALIA, 
 
 27 
 
 The number of vertebrse in this division is generally 
 seven, whether the neck be long, as in the giraffe, or 
 short, as in the whales. The only exceptions to this 
 rule are, the three-toed sloth, which has nine neck bones ; 
 and the manatee, which has six. 
 
 2. The dorsal (Lat. dorsum, the back) region. The 
 number of vertebrse in this* region varies from ten to 
 fifteen or more. The usual number is twelve or thirteen. 
 To the dorsal vertebrse the true ribs are attached. 
 These enclose the cavity of the chest, and are united . 
 in front by cartilages to the sternum or breast bone. 
 
 FHJ. 4. DORSAL VERTEBRA WITH ATTACHED RIBS. 
 
 act, neural arches; snx, neural canal ; v, vertebral centre; a 'a', ribs enclos- 
 ing the visceral cavity, snf; b l b', cartilages; c', sternum. 
 
 3. The lumbar (Lat. lumbus, a loin) vertebrse occupy 
 the region of the loins. They vary in number from four 
 to seven. There are four in man. 
 
 4. The sacral bones which follow vary from one to nine 
 in number. They are anchylosed, or immovably joined 
 together, so as to form a single bone. 
 
 5. The caudal (Lat. cauda, the tail) or tail vertebrre 
 range from four to forty-six. They move more freely 
 upon, one another than the other vertebrse. 
 
ZOOLOGY. 
 
 25, There are usually four limbs present, but the whale 
 tribe have only the front pair. On this account the 
 mammalia are often called quadru- 
 peds. This term, however, would also 
 include the amphibia and most reptiles. 
 The fore limb is joined to the trunk 
 by the scapula or shoulder blade, and 
 the clavicle or collar bone. The upper 
 part of the limb consists of a single 
 bone, called the humerus ; the lower 
 part of two bones, the radius and 
 ulna ; then follow the carpal or wrist 
 bones, the metacarpal bones, which 
 form the upper part of the hand, and 
 the phalanges, or bones of the fingers 
 or toes. 
 
 The parts of the hind limb are simi- 
 lar to those just mentioned ; but they 
 are called by different names. The 
 hind limb is joined to the trunk by a 
 number of bones, which are generally 
 anchylosed together, and termed the 
 innominate bone. To this is joined 
 the femur or thigh bone ; then the leg 
 bones, tibia and fibula; the tarsus 
 or ankle bones; the metatarsus, or 
 bones of the foot; and the phalanges 
 a, clavicle or collar- of the toes. There are usually five 
 fei^oTrhumeru" 1 ; digits, with three phalanges in each. 
 d, radius ; e, ulna;/, car- The horse, however, has only one 
 
 pal or wrist-bones; g, ,. ., ,. 7 , ,, j n 
 
 metacarpus or bones of digit, corresponding to the middle 
 finger. The ox has bones corre- 
 sponding to two fingers; and there 
 variations from the rule found in some of 
 
 FIG 5. FORE LIMB OP A 
 MAN. 
 
 the hand ; h, phalanges 
 or finger-bones. 
 
 are other 
 the carnivora. 
 
 26. Digestion. Except the Baleen whale and the great 
 ant eater, all mammals possess teeth, which are inserted 
 in distinct sockets in the jaws. They have generally two 
 
VERTEBEATA MAMMALIA. 
 
 sets of teeth; the first, termed the milk or deciduous 
 teeth, being succeeded by the permanent teeth. Gen- 
 erally, there are four different sorts of teeth present 
 incisors, canines, praemolars, and 
 molars. The exceptions to this rule 
 are numerous, the number and varie- 
 ties of teeth present differing much 
 in the various "orders" into which 
 the class Mammalia is divided. 
 
 The food during mastication is mixed 
 with a substance called saliva, secreted 
 by the salivary glands. These glands 
 are absent in the whales. It then 
 passes through a tube called the oeso- 
 phagus or gullet into the stomach, 
 where it is acted upon by a fluid termed 
 the gastric juice. By means of this 
 fluid it is converted into a substance 
 called chyme. This chyme passes 
 through the small intestine, where 
 it is acted upon by the bile, secreted 
 by the liver; and the pancreatic 
 juice, produced by another gland 
 called the pancreas. 
 
 " The special function of the sali- 
 vary glands is to digest the starch 
 compounds of the food; and the special Fm< 6> _ HlND LlMB OP 
 function of the gastric juice is to di- ' A MAN. 
 gest the nitrogenous elements of the &, femur or thigh hone; 
 food; the remaining or fatty elements g^j. &"&' : 
 of food are, in like manner, digested, /, metatarsus; g, pha- 
 and prepared for assimilation by the 2" 
 pancreatic juice." (Dr. Haughton.) 
 
 By these fluids the chyme is changed into a milky 
 substance termed chyle, which is conveyed to the blood- 
 vessels by a set of tubes called lacteals. 
 
 The small intestine is followed by a wider tube termed 
 the large intestine, which is provided at the outer 
 
30 
 
 ZOOLOGY. 
 
 extremity by an opening called the anus. Through 
 this tube the indigestible portions of the food are car- 
 ried off as excrement. 
 
 27. Circulation. The heart, 
 which is surrounded by a mem- 
 branous sac called the peri- 
 cardium, contains four cham- 
 bers. The right side consists 
 of two cavities, the right auricle 
 and the right ventricle; the left 
 side has two similar cavities, 
 the left auricle and the left 
 ventricle. The blood passes 
 from the auricles to the ven- 
 Itricles; but, the apertures being 
 F guarded by valves, it cannot 
 1 pass from the ventricles to the 
 auricles. There is no com- 
 munication between the right 
 and left sides of the heart. 
 
 Two great veins, the su- 
 perior and inferior venae caV8B, 
 receive the impure or venous 
 blood from the entire body, 
 and pour it into the right 
 auricle, from which it passes 
 to the right ventricle. From 
 this chamber it is driven to 
 the lungs through the pulmonary artery, where it is 
 changed by the oxygen of the air into arterial blood. 
 The pulmonary veins convey it back to the left auricle, 
 from which it passes to the left ventricle, and is by it 
 propelled through the aorta and its numerous branches to 
 the various parts of the body. 
 
 The greater number of the corpuscles are red. 
 They are circular in form, except in the camels, and 
 are destitute of any solid particle or nucleus. The 
 blood is hot. 
 
 Fio. V - -DIGESTIVE SYSTEM OF A 
 MAMMAL. 
 
 e, rectum. 
 
VERTEBRATA MAMMALIA. 
 
 31 
 
 28. Respiration. The thorax or chest is separated 
 from the abdomen by a muscular partition called the 
 diaphragm, which plays an important part in the work of 
 respiration. In the abdomen are 
 
 placed the greater part of the 
 alimentary canal, the stomach, 
 the liver, kidneys, &c. The heart 
 and lungs are situated in the 
 thorax. There are two lungs, 
 which are spongy and elastic, and 
 abound in air cells. They are 
 freely suspended in the cavity of 
 the thorax, and each of them is a __ 
 enclosed in a membranous sac 
 called the pleura (Or. pleura, 
 the side). Their bronchi, or 
 branches of the windpipe which 
 traverse them, never communi- 
 cate with air sacs in the body, as 
 those of birds do. 
 
 29. Nervous System. The 
 brain in the Mammalia is much 
 larger than in the other verte- 
 
 brates. The two hemispheres of vena cava; & right auri- 
 
 , . y , cle ; c, right ventricle ; d, pul- 
 
 the Cerebrum, Or principal maSS monary artery ; e, pulmonary 
 
 of the brain, are united by a ^^i^SSMff. 
 
 band of nerve fibres termed the laries of the lungs; i 1 , capii- 
 corpus callosum (Lat. "the firm SS^^SSSu Theven ~ 
 body"). 
 
 30. Sight and Hearing. All mammals possess eyes, but 
 in some instances the sight is very imperfect. Except 
 the whales, and some of the seals, all have an external 
 ear. 
 
 31. Covering. The covering consists of hair, which is 
 only found in this class. Hair is of the same nature as 
 feathers, but does not split up as feathers do. It is 
 always developed by some part of the skin, except in 
 the whales and the scaly ant-eater. In the hedgehog 
 
 Fm 8 ._ CmcuLATION OF A 
 MAMMAL. 
 
32 ZOOLOGY. 
 
 and porcupine the hairs take the form of spines. The 
 armadilloes are partly covered with bony plates. 
 
 32. The members of this group are usually arranged in 
 two* great divisions or sub-classes : 
 
 1. Placental mammals. 
 
 2. Non-placental mammals. 
 
 The placenta (Lat. placenta, a cake) is a structure de- 
 veloped by the allantois, and composed of vascular tissue. 
 The young of mammals, possessing this placenta, remain 
 for a considerable period within the body of the mother, 
 where they are nourished by arterial blood supplied 
 through the minute vessels of this organ. In the iion- 
 placental mammals the young are brought forth much 
 earlier ; and, not having been nourished by a placenta, 
 are born in a very imperfect condition. They are then 
 placed by the mother within a "pouch" beneath the 
 abdomen, where they become attached to the nipple; and, 
 being unable to obtain the milk by suction, it is forced 
 into their mouths by a special muscle connected with the 
 mammary gland. 
 
 CLASS II. Aves. 
 
 33. Aves (Lat. avis, a bird) or birds form the second 
 class of vertebrate animals. 
 
 As already stated, birds have been placed along with 
 reptiles in the section of the Vertebrata which has been 
 termed Sauropsida. The points of agreement are : At 
 no period of life are gills present ; the skull is joined to 
 the vertebral column by a single condyle on the occipital 
 bone ; the lower jaw is composed of several pieces, and is 
 united to the skull by a quadrate bone ; the red blood- 
 
 * Professor Huxley, following De Blainville, divides mammals 
 into three sub-classes : 
 
 1. Ornithodelphia, which embraces the order Monotremata. 
 
 2. Didelphia, which corresponds to the Marsupialia. 
 
 3. Monodelphia, which includes all other mammals. (See Hux- 
 ley's Classification of Animals. ) 
 
VERTEBRATA AVES. 33 
 
 corpuscles are oval and nucleated ; the embryo is provided 
 with an amnion and an allantois. 
 
 34. Skeleton. In order to adapt birds for flight, the 
 skeleton is remarkable for its combined lightness and 
 strength. There is a larger proportion of phosphate of lime 
 present than in the bones of mammals ; and in adult birds, 
 many of the bones are filled with air instead of marrow. 
 
 In full grown birds, the various bones that form the 
 skull, are amalgamated into a single piece. There is only 
 a single condyle on the occipital bone, as in the 
 reptiles. In young birds, each half of the lower jaw 
 consists of six pieces ; but these, in the mature animal, are 
 so amalgamated, that the lines of junction cannot be dis- 
 tinguished. The lower jaw is joined to the quadrate 
 bone, and not directly to the skull, as in the mammalia. 
 
 The neck is long and flexible, and consists of from nine 
 to twenty-four, vertebrae. As the beak is the only organ 
 of prehension possessed by these animals, such a neck is 
 required to enable them to procure their food. It is also 
 long enough to reach a gland situated at the base of the 
 tail, where the oil with which they trim their feathers is 
 secreted. 
 
 There are from six to ten dorsal vertebrae, several of 
 which are anchylosed together. By this arrangement, 
 that part of the vertebral column is made sufficiently 
 strong to bear the strain caused by the motion of the 
 wings in flight. In birds, however, that do not fly, such 
 as the ostrich tribe and the penguins, the dorsal vertebrae 
 are movable upon each other. 
 
 The vertebrae between the dorsal and caudal regions of 
 the spine are amalgamated into a single bone called the 
 sacrum, which is anchylosed with the innominate bones 
 to form the pelvic arch. 
 
 The innominate bones are always anchylosed together, 
 but are never united below, except in the ostrich. 
 
 The caudal vertebrae, eight to ten in number, are more 
 or less movable. The last joint, which consists of several 
 vertebrae anchylosed together, is ? from its shape, termed 
 15 E. C 
 
34 
 
 ZOOLOGY. 
 
 the " ploughshare bone," and is nearly perpendicular to 
 the vertebral column. It supports the large quill feathers 
 of the tail. In an extinct bird, the archseopteryx (Gr. 
 archaios, ancient ; pteryx, a wing), whose remains are 
 found in the oolitic rocks, there was no ploughshare bone, 
 and the tail consisted of twenty distinct vertebrae, each of 
 which bore a pair of quill feathers. 
 
 The sternum is very large, and in flying birds is pro- 
 vided with a ridge or "keel." To the sternum, the muscles 
 which move the wings are attached. The keel is absent 
 in the Cursores, an order which includes the ostrich, 
 emeu, cassowary, &c. The number of ribs varies from 
 seven to eleven pairs. 
 
 FIG. 9. STERNUM, FURCULUM, SCAPULAE, AND CORACOID BONES OP 
 A SPARROW. 
 
 The scapula, clavicle, and coracoid bone form what is 
 called the " pectoral arch." The clavicles are united in 
 front, forming a Y-shaped bone, which is termed the 
 furculum (Lat. furca, a fork) or " merrythought." The 
 coracoid (Gr. Jcorax, a crow) bone corresponds to the 
 " coracoid process" in man, but in birds is a distinct 
 bone. It is united at one end to the clavicle and scapula, 
 at the other to the sternum. 
 
 Of the fore-limb or wing, the upper bone is the 
 
VERTEBRATA ^AVE8\ 35 
 
 humerus, which is united to the pectoral arch, and is 
 followed by the radius and ulna. The radius is very 
 slender. Then follow two small carpal bones, and two 
 metacarpal bones, which are anchylosed at both ex- 
 tremities. There is a rudimentary thumb situated at the 
 upper end of the metacarpal bones. This thumb consists 
 of a single joint, and carries the " bastard wing." The 
 metacarpal bones support two " fingers," which corre- 
 spond to the index and middle fingers of the human hand. 
 One of the fingers consists of a single phalanx or joint; 
 the other has two or three. 
 
 Fia. 10. Wma OF A SPARROW. 
 
 With regard to the structure of the hind limb, there 
 is a very short femur united to the " pelvic arch." This 
 is followed by the tibia, to which a very thin fibula is 
 anchylosed. The upper part of the tarsus is amalgamated 
 with the tibia, and the lower portion with the metatarsus, 
 forming the bone called the tarso-metatarsus. In the 
 waders this bone is very long. 
 
 There are usually four toes, but some domestic birds 
 possess a fifth toe. Three of the toes are commonly 
 placed before, and one behind. One group, however, has 
 two before and one behind. The swifts have the whole 
 four directed forwards. In several of the swimmers, and 
 
ZOOLOGY. 
 
 Fia. 11. SKELETON OF COCK. 
 
 c r, the cranium; v c, cervical vertebrae; c I, the furculum or merrythought; 
 c r, coracoid bone ; s t, sternum ; v d } dorsal vertebrae ; o i, innominate bone ; 
 v c c, caudal vertebrae ; h s, humerus ; c s, ulna ; r s, radius ; m t c, metacarpus; 
 2> h, phalanges; fr, femur; t b, tibia; p r, fibula; in 1 1, tarso metatarsus; ph' 9 
 phalanges of the toes. 
 
VERTEBEATA AYES. 
 
 37 
 
 in the emeu and cassowary, the hind toe is wanting or 
 rudimentary. The African ostrich has only two toes. 
 The hind toe, when present, has two, the innermost three, 
 the next four, and the ff 3 ] 
 
 third five phalanges. 
 
 35. Digestion. 
 Birds are destitute of 
 teeth. The mandibles 
 or jaws are sheathed 
 with a horny substance 
 forming a beak. They 
 are provided with sali- 
 'vary glands, which 
 are much smaller than 
 in mammals. The food 
 passes through, a long 
 gullet into a pouch 
 called the crop, where 
 it remains for some 
 time. This crop, which 
 may be considered an 
 expansion of the gul- 
 let, is wanting in some 
 birds. It is then trans- 
 ferred to the true di- 
 gestive stomach, where 
 it is mixed with the 
 gastric j nice. Having 
 been imperfectly mas- 
 ticated, owing to 
 
 absence of teeth, the cular waif of gizzard; g, duodenum; ' h', small 
 
 f^ J CL 1 xi intestine ; ii, intestinal cceca ; Jc. commence- 
 
 lOOd, after leaving tllO ment O f large intestine; l t cloaca; w, liver; 
 
 true Stomach, is COn- ', pancreas. 
 
 veyed to a muscular bag, called the gizzard, provided with 
 a rough horny lining, which, assisted by gravel swajfewed 
 by the bird, reduces it to a pulpy mass. This kind of gizzard 
 is found in grain-eating birds only. In birds of prey which 
 live upon flesh its coats are thinner, and it is a much less 
 
 FlG> IO.-DIGESTIVE APPARATUS OF TUB 
 COMMON HEN. 
 
 a, the lower part of the oesophagus ; 6, crop ; 
 Mr ' ue digestive rtomach; d, gizzard; e, m us- 
 
38 ZOOLOGY. 
 
 powerful organ. The food, after leaving the gizzard, 
 passes into the small intestine, where it is acted upon by 
 the bile and pancreatic juice. The large intestine, which 
 is very short, passes into a bladder-like cavity called 
 the cloaca (Lat. cloaca, a sink), which also receives the 
 secretions of the kidneys and the genital organs. There 
 is a similar arrangement in reptiles. 
 
 36. Circulation. The mean temperature of the blood of 
 birds is 110, while that of mammals is about 100. The 
 higher temperature is partly due to the great activity of 
 these animals, and partly to the " double respiration," by 
 which the blood is aerated in the air sacs of the body, as 
 well as in the lungs. The covering of feathers, which' 
 are bad conductors of heat, assists in keeping up the high 
 temperature. 
 
 The red corpuscles of the blood are oval in shape, and 
 contain a central solid particle or nucleus. 
 
 The structure of the heart and the nature of the 
 circulation in birds and mammals are very much alike. 
 The heart has four chambers, two auricles and two 
 ventricles; and the right and left sides have no com- 
 munication with each other. The venous blood is received 
 from the body into the right auricle. It then passes 
 into the right ventricle, which sends it to the lungs, 
 through the pulmonary artery. Having been aerated in 
 these organs, and changed into arterial blood, it is con- 
 veyed by the pulmonary veins to the left auricle, thence 
 to the left ventricle, which drives it through the aorta 
 and its branches to all parts of the body. 
 
 The valve which separates the right auricle from the 
 right ventricle, instead of being "tricuspid" as in mam- 
 mals, is of a triangular form. The action of the heart is 
 more rapid than in mammals, and its walls and valves 
 are relatively stronger. 
 
 37. Eespiration. Birds have two lungs of a bright red 
 colour, and spongy structure. They are placed at the 
 back of the chest, and are not suspended in a pleura! 
 membrane, as in mammals, 
 
VEHTEBKATA AVES. 
 
 Fia. 13. RESPIRATORY APPARATUS OF THE HEN. 
 
 6 trachea c bronchus d, spongy part of lungs ; e, air sac situated in the 
 bre'astT/, air sacs uitSe region^ the shoulders ; g and ft, large air sacs placed 
 ia the abdomen. 
 
40 ZOOLOGY. 
 
 The cavities of the chest and abdomen are not se- 
 parated by a diaphragm, this partition being only 
 rudimentary. 
 
 The bronchial tubes communicate by a series of open- 
 ings on the surface of the lungs with a number of air 
 sacs situated partly in the chest, and partly in the 
 abdomen. These sacs are connected with the interior of the 
 bones, which also contain air cells. As has been already 
 stated, the blood is aerated in these air-receptacles as well 
 as in the lungs. By filling these sacs with air, the animal 
 is enabled to reduce its specific gravity at will. 
 
 There are no air-cells in the bones of the penguin and 
 some other aquatic fowls; and only a few of the bones in 
 the ostrich tribe are " pneumatic." 
 
 38. Nervous System. The brain is relatively smaller 
 than in mammals, and is without convolutions. The two 
 hemispheres of the cerebrum are not united by a corpus 
 cattosum. 
 
 39. Senses. The eyes of birds are in front, of a conical 
 shape, and possess a third eyelid. The sense of sight is 
 always very acute. There is no external ear. The 
 nostrils are placed on the sides of the upper mandible. 
 They are sometimes surrounded by bristles, and are 
 sometimes covered by a cartilaginous scale. 
 
 40. Covering. Feathers form the peculiar covering of 
 birds. Being non-conductors of heat, they assist in keep- 
 ing up the high temperature of the body. A feather 
 consists of several distinct parts. First, there is a horny 
 tube, called the quill ; then the shaft, which has a horny 
 surface, with a groove on the under side; the interior 
 being filled with a pith-like substance. The webs are 
 situated at the sides of the shaft. The divisions of the 
 web are called barbs, each of which is covered with a 
 number of barbules. Generally, the barbs are kept 
 together by the barbules, which are provided with hooks 
 for this purpose. In the ostrich tribe, however, the 
 barbs are disconnected. 
 
 There is an oil gland at the base of the tail, with the 
 
VERTEBRATA REPTILIA. 41 
 
 secretions from which they anoint their feathers, and thus 
 ^render them impervious to moisture. 
 
 41. Development. Birds are oviparous (Lat. ovum, an 
 egg ; pario, I bring forth) animals. The ovary is situated 
 011 the left side. During the passage of the egg through 
 the oviduct, it receives, first, the " white " or albuminous 
 covering with which the embryo is nourished; and, after- 
 
 rds, the calcareous shell, with which it is covered. 
 From the oviduct it reaches the cloaca, and passes thence 
 to the outer world. It is then subjected for a longer or 
 shorter period to a process of incubation, by which the 
 chick is fully developed. To enable it to break the shell, 
 the bill of the young bird is provided with a protuber- 
 ance of calcareous matter, which afterwards disappears. 
 
 Those birds which have been termed Autophagi (Gr. 
 dittos, self ; pJiago, I eat) are able to run about and provide 
 for themselves, as soon as they leave the shell. The other 
 section, Heterophagi (Gr. heteros, other ;phago, I eat), come 
 from the egg, blind and naked; and require to be protected 
 from cold, and fed by the parent birds for a considerable time. 
 
 CLASS III. Eeptilia. 
 
 42. The Reptilia (Lat. repto, I creep) form the third 
 class of vertebrate animals, and the second of the section, 
 Sauropsida. This class includes crocodiles, lizards, 
 serpents, turtles, and tortoises. 
 
 They possess the following characters in common with 
 birds : They are oviparous, or ovoviviparous, animals ; 
 the embryo is provided with the membranes termed 
 amnion and allantois ; there are no mammary glands ; 
 at no period of life are gills present ; the skull is joined 
 to the vertebral column by a single occipital condyle ; 
 each half of the lower jaw consists of several pieces ; the 
 lower jaw is not united directly with the skull, but to an. 
 intervening quadrate bone ; the alimentary canal termi- 
 nates in a cloaca ; the red corpuscles of the blood are oval 
 in shape and contain a central solid particle or nucleus ; 
 
42 
 
 ZOOLOGY. 
 
 the cavities of the chest and abdomen are not separated 
 by a diaphragm ; the hemispheres of the brain are not 
 united by a corpus callosum. 
 
 On the other hand, reptiles differ from birds in the 
 following particulars : The covering of reptiles consists 
 of horny scales, and sometimes, also, of bony plates, never 
 of feathers ; the fore-limbs never take the form of wings ; 
 the tarsal and metatarsal bones of the hind limb are never 
 anchylosed ; the heart generally contains three cavities, 
 and the blood is cold : the bronchi of the lungs never 
 terminate in air sacs. 
 
 43. Skeleton. The vertebral column varies much in the 
 different groups. Some serpents have as many as three 
 hundred vertebrae, united by a "ball and socket" joint. 
 The tail is generally very long. The limbs, when pre- 
 
 FIG. 14. SKULL OP A VIPER. 
 a, view from above ; &, from below ; c, side view. 
 
 sent, are sometimes used in walking, sometimes in 
 swimming, and in the extinct pterodactyles (Gr. pteron, 
 a wing ; daktulos, a finger) as organs of flight. In this 
 last case, however, the skeleton of the fore-limb had no 
 resemblance to the wing bones of a bird. The serpents 
 and some lizards are destitute of limbs. 
 
 There is a single condyle on the occipital bone, and a 
 corresponding facet on the atlas. There are from four to 
 six pieces in each half of the lower jaw, which is united 
 
VERTEBRATA REPTILIA. 43 
 
 to the skull by a quadrate bone. The various pieces, as 
 well as the two halves, are anchylosed in the tortoises. 
 In the snakes the two halves of the lower jaw are only 
 united by muscles and ligaments. 
 
 44. Digestion. All reptiles, except the turtles and tor- 
 toises, possess teeth. The teeth in the various parts of the 
 jaw are all of the same kind, and, except in the crocodiles, 
 are not inserted in separate sockets. The tortoises and 
 turtles have horny beaks instead of teeth. Generally 
 speaking, there is not much peculiarity in the digestive 
 system of the Reptilia. Salivary glands are sometimes 
 absent. In serpents the stomach is but little different 
 from the gullet and intestine ; in crocodiles it bears a 
 considerable resemblance to the gizzard of birds. The 
 crocodiles also swallow pebbles to assist in grinding the 
 food. The numerous conical teeth with which these 
 animals are provided, are better adapted for holding the 
 food than for masticating it. The intestine, as in birds, 
 opens into a cloaca, which also receives the secretions of 
 the kidneys and genital organs. 
 
 45. Circulation. In mammals and birds the heart 
 always contains four cavities two auricles and two ven- 
 tricles ; and the right and left sides are always distinct, the 
 chambers of the right side containing only venous blood, 
 and the left side arterial blood. In reptiles the heart has 
 always two auricles ; sometimes one, and sometimes two 
 ventricles. When there is only one ventricle, the follow- 
 ing is the course of the circulation : The impure venous 
 blood from the body is poured by the venae cavse into 
 the right auricle, thence into the ventricle ; the arterial 
 blood is conveyed by the pulmonary veins to the left 
 auricle, and passes also into the ventricle. This cavity 
 thus contains a mixture of venous and arterial blood. 
 This mixed fluid is driven by the ventricle, partly to the 
 lungs by the pulmonary artery, and partly by the aorta 
 to all parts of the body. 
 
 In the crocodiles there is a complete partition between 
 the two ventricles, the heart in this group containing four 
 
ZOOLOGY. 
 
 chambers. On this account, the mixture of arterial and 
 venous blood cannot take place within the heart itself ; 
 but the pulmonary artery and aorta are connected by a 
 small aperture near their origin. Through this aperture, 
 the venous blood contained in 
 the pulmonary artery is mixed 
 with the arterial blood con- 
 tained in the aorta. Thus, 
 in the crocodiles, a mixed fluid 
 is conveyed to the lungs and 
 through the system, as well as 
 in the other Reptilia. 
 
 On account of this peculiarity 
 in the structure of the heart, 
 and in the course of the circu- 
 lation, the blood of the Reptilia, 
 being imperfectly aerated, is 
 cold ; and, as a consequence, 
 the movements of these animals 
 are sluggish, and their intelli- 
 gence of a lower order. " It 
 may be remarked, however, 
 that stupidity in reptiles is as- 
 sociated, as it often is in man, 
 with a venomous and rancor- 
 ous disposition; and that these 
 FIG. is.-Cm^ATioN IN REPTILES. Defects, both intellectual and 
 a, vena cava ; &, right auricle, moral, seem to depend upon an 
 
 receiving venous blood from the ^^p-fp^- /yjn'rhtirm nf fho 
 
 body; c, left auricle, receiving ar- iniper 
 
 terial blood from the lungs; d, blood Corpuscles. (Dr. 
 
 common ventricle, receiving mixed 7-7- ,, \ 
 
 blood; e, pulmonary artery, con- a.ClugtltOn.J 
 
 veying mixed blood to the lungs; rj^ ^ corpuscles of the 
 
 /, aorta, conveying mixed blood r 
 
 through the system. blood are oval and nucleated. 
 
 46. Respiration. The cavities of the chest and abdomen 
 are not separated by a diaphragm. The lungs are large 
 and often extend into the abdomen. Their bronchi are 
 closed, and do not communicate with air sacs in the body. 
 In the serpents, there is only a single lung. 
 
VERTEBRATA AMPHIBIA. 45 
 
 47. Nervous System. The brain is relatively smaller 
 than in the birds or mammals. The surfaces of the hemi- 
 spheres of the cerebrum are without convolutions. There 
 is no corpus callosum. 
 
 48. Covering. The covering of reptiles consists of horny 
 scales developed by the epidermis (Gr. epi, upon ; derma, 
 the skin) or cuticle ; and in the crocodiles, tortoises, and 
 turtles, there are also bony plates, formed by the derma 
 or true skin. 
 
 49. Development. All reptiles are oviparous. The 
 outer coating of the egg is usually leathery, instead of 
 being calcareous as in the birds. Sometimes the egg 
 undergoes the necessary incubation within the body 
 of the mother, so that the young is developed before 
 the exclusion of the egg. Such reptiles are said to be 
 ovoviviparous, 
 
 CLASS IY.- Amphibia. 
 
 50. The term Amphibia (Gr. amphi, both; bios, life) was 
 formerly applied to aquatic mammals, such as the seals ; 
 but it is now restricted to a group of animals, including the 
 frogs, toads, and newts, which at one period of life are 
 adapted for breathing in water, and afterwards for breath- 
 ing in air. 
 
 The Amphibia and the fishes form the section of the 
 Yertebrata termed Ichthyopsida. They resemble fish in 
 the following details: They are oviparous; the embryo 
 is destitute of the membranes termed amnion and 
 allantois; gills or organs adapted for breathing the air 
 dissolved in water are always present at some period 
 of life; there is no diaphragm; the red blood-cor- 
 puscles are oval and nucleated; there are no mammary 
 glands. 
 
 51. Skeleton. The skull, as in the mammalia, unites 
 with the vertebral column by two occipital condyles; but 
 the " basi-occipital" is cartilaginous not bony, as in the 
 higher Yertebrata. There are two corresponding cups in 
 
46 ZOOLOGY. 
 
 the atlas. This structure furnishes a ready means of distin- 
 guishing the skull of an amphibian from that of a reptile. 
 
 52. The limbs, when present, resemble in their structure 
 those of the higher Vertebrata. In the fore-limb there 
 is a humerus, followed by radius and ulna, carpus, 
 meta-carpus, and phalanges; and in the hind limb a 
 femur, tibia, and fibula, tarsus, meta-tarsus, and 
 phalanges. These parts sometimes consist of bone ; in 
 other cases, of cartilage. 
 
 53. Digestion. The mouth is of large size, and is 
 generally furnished with small conical teeth. There is a 
 liver, divided into two lobes; a gall-bladder, pancreas, 
 and spleen. The intestine, which is short, opens, as in 
 the Reptilia, into a cloaca, which also receives the secre- 
 tions of the kidneys and generative organs. 
 
 54. Respiration. The nature of the respiratory organs 
 forms the most distinctive feature of the Amphibia. In 
 the larval or young state, they all possess gills which en- 
 able them to breath the air contained in water. These 
 gills are external filaments, situated on the sides of the 
 neck. In the frogs, toads, and newts, there are two sets 
 of gills ; one external, which soon disappears, and one 
 lodged in an internal chamber, which remains for a 
 longer period. All the Amphibia possess lungs in the 
 adult state. Generally the gills disappear when the 
 lungs are developed, but sometimes the external gills are 
 retained through life, the animal in this case possessing 
 both lungs and gills. 
 
 The nasal sacs always open posteriorly into the mouth. 
 
 55. Circulation. In the young state, so long as they 
 breathe by gills, the circulation of the Amphibia is similar 
 to that of fishes, the heart containing only two cavities, 
 an auricle and a ventricle. When the lungs are de- 
 veloped, however, the auricle is divided, and the heart 
 then contains three chambers, as in the greater number 
 of reptiles. The venous blood from the body passes to 
 the right auricle, and the arterial blood from the lungs 
 to the left auricle; both these chambers pour their con- 
 
VERTEBRATA AMPHIBIA. 
 
 47 
 
 tents into the common ventricle, which drives this mixed 
 fluid partly through the system, and partly to the lungs. 
 The blood is cold. The red corpuscles are oval, and 
 contain a central nucleus. 
 
 FIG. 16. METAMORPHOSIS OP TOAD. 
 
 a, ova; &, tadpoles just hatched; &', tadpole enlarged to show external 
 gills; c, tadpole after losing external gills; d, the same after development 
 of posterior limbs ; e, provided with both pairs of limbs ; /, tail begins to dis- 
 appear; g, tail almost wholly absorbed. 
 
 56. Covering. The covering consists of a soft moist 
 skin, which is generally destitute of scales. 
 
 57. Development. The Amphibia all undergometamor- 
 phosis (Gr. meta, change; morphe, form). The eggs are 
 
48 ZOOLOGY. 
 
 deposited in water in a mass. They are destitute of shells. 
 Each ovum consists of a black yelk, surrounded by a 
 gelatinous "white." The ova are impregnated by the 
 male immediately after exclusion. If a quantity of the 
 spawn of the common frog is placed in water in a glass 
 vessel, the following phenomena will be observed. After 
 a time small fish-like animals will proceed from the dark 
 specks of yelk. These, if viewed by a microscope, will 
 be seen to be destitute of feet, to possess external gills in 
 the form of branched tufts, and a long tail, surrounded 
 by a "median fin," unsupported by rays. After a time the 
 ijflls decay, the hind feet are developed, then the fore- 
 feet. The tail is gradually absorbed into the body, and 
 finally disappears altogether. In the newts the fore-feet 
 make their appearance first, and the tail is retained. 
 
 CLASS Y.Pisces. 
 
 58. The Pisces or fishes (Lat. piscis, a fish) form the last 
 class of vertebrate animals. These animals live entirely 
 in water, and for this mode of life they are admirably 
 adapted, the shape of their bodies, and the arrangement 
 of the scales with which they are covered, presenting 
 the least possible resistance to the medium through which 
 they move. 
 
 Fishes form the second class of the section IchtJiyop- 
 sida. They agree with the Amphibia in breathing by 
 gills which are permanent; in being destitute of the 
 membranes ainnion and allantois in the embryonic state ; 
 in possessing cold blood, and in having oval, nucleated, 
 red blood-corpuscles. They are also, like the Amphibia, 
 oviparous animals. 
 
 They differ from the Amphibia in being covered with 
 scales instead of having a naked skin ; in possessing a 
 heart with only a single auricle and a ventricle. In the 
 fishes also, the nasal cavities do not open behind into the 
 pharynx, as is the case with all the higher Vertebrata. 
 
VERTEBRATA PISCES. 49 
 
 The gills remain throughout life, and the limbs take the 
 form of fins. 
 
 59. Skeleton. The internal skeleton of some fishes 
 consists of cartilage or gristle ; in others it is partly 
 composed of cartilage and partly of bone. Most of the 
 extinct fishes, especially of those found in the primary 
 rocks, had cartilaginous skeletons ; but the skeletons of 
 the majority of modern fishes consist of true bone. 
 
 In cartilaginous fishes the various parts of the skull 
 are joined together so as to form a single piece ; but in 
 the bony fishes the skull is very complex. 
 
 The number of vertebrse is very various, ranging in 
 different fishes from seventeen to one hundred. In bony 
 fishes, the vertebrae are amphicoelus (Or. amphi, both; 
 koiloSj hollow) or concave at both ends. Their edges are 
 united together by ligaments, and the hollow space 
 between the vertebraB is filled with a gelatinous substance, 
 so that the spine is extremely flexible. The vertebral 
 column is divisible into the two regions caudal and 
 abdominal. The ribs are confined to the abdominal 
 region. Their lower ends are free, the sternum being 
 absent. 
 
 60. The limbs, when present, take the form of " fins," 
 which are prolongations of the integument or skin, sup- 
 ported by bony or cartilaginous rays. The pair of fins 
 which correspond to the arms of a man are called pectoral 
 (Lat. pectus, the breast) fins. They are attached to bones 
 which bear some resemblance to the fore-arm in the 
 higher vertebrates. There is a pectoral arch in which 
 the scapula, clavicle, and coracoid bones are represented. 
 The humerus is wanting ; but there are usually bones to 
 represent the radius and ulna, and the carpus. To this 
 latter the fin rays are attached. 
 
 61. The ventral (Lat. venter, the belly) fins correspond 
 to the legs of a man. They are united directly to a kind 
 of pelvic arch, the bones of the hind limb being unre- 
 presented. Besides these fins, which are called paired 
 fins, there are others which occupy the middle line of the 
 
 15 E. D 
 
50 ZOOLOGY. 
 
 body, and are, for this reason, termed median fins. 
 These fins are joined to a series of pointed bones called 
 interspinous bones, which are connected at their inner 
 ends by ligaments with the spinous processes of the 
 vertebrae. The median fins on the back, one or two in 
 number, are called dorsal (Lat. dorsum, the back) fins; 
 
 it' 
 
 FIG. 17. SKELETON OF THE PERCH. 
 
 /, operculum; gg f , vertebral column; h, one of the pectoral fins; i t ventral 
 fin ; kl, first and second dorsal fins, supported OD interspinpus bones; m anal 
 fin, with its interspinous bones . 
 
 those near the vent, anal fins; and the fin at the ex- 
 tremity of the vertebral column is termed the caudal 
 (Lat. cauda, the tail) or tail fin. The median fins of 
 fishes differ from those that are met with in the larvae of 
 the Amphibia, in being supported by " fin rays." The 
 caudal fin, which is the principal agent in locomotion, is 
 always placed vertically, and not horizontally as in the 
 whale tribe. 
 
 There are two types of caudal fin, homocercal (Gr. 
 homos, same; herlcos, a tail), and heterocercal (Gr. heteros, 
 different; Jcerkos, a tail). In the homocercal type, the ver- 
 tebral column terminates at the commencement of the tail 
 lobes, which are of the same shape and of equal size, In 
 
VBBTBBBATA PISCES. 
 
 81 
 
 the heterocercal type, the vertebral column extends to 
 the extremity of the upper tail lobe. The greater por- 
 tion of the caudal fin is in 
 this case below the vertebral 
 column, the lobes being un- 
 equal. Most modern fishes 
 have homocercal tails, while 
 the heterocercal type is com- 
 monest in fossil fishes. The 
 sturgeons, sharks, &c., have 
 heterocercal tails. 
 
 62. Digestion. Theteeth 
 of fishes are not confined to 
 the jaivs, but are usually 
 distributed over all the bones 
 which assist in forming the 
 cavity of the mouth They 
 are not inserted in sockets, 
 
 being merely attached to the FIG. 18. TAIL FINS OP FISHES. 
 
 Surface of the bones. The 1, homocercal tail; 2, heterocercal tail. 
 
 gullet, which is short and wide, opens into a large stomach. 
 The inner extremity of the stomach, where it opens into 
 the intestine, is furnished with a valve, behind which are 
 a number of blind tubes, termed the "pyloric cseca," 
 which are thought to be the representatives of the pan- 
 creas. A true pancreas, however, is sometimes present. 
 The intestinal canal varies in length in different fish. 
 The liver is usually large, and contains much oil. The 
 kidneys are also so large as to .extend from the one 
 extremity of the abdomen to the other. 
 
 63. Circulation. The heart generally consists of two 
 cavities, an auricle and a ventricle. The exceptions are 
 the Arnphioxus or Lancelet, which has no heart, and the 
 Lepidosiren or mud-fish, which has two auricles and one 
 ventricle. The venous blood, after traversing the body, 
 passes through the vena cava into the auricle which trans- 
 mits it to the ventricle. It passes from the ventricle into 
 the "branchial artery" which conveys it to the gills, 
 
52 
 
 ZOOLOGY. 
 
 where it is purified by the action of the air contained in 
 the water. This artery, at its base, where it leaves the 
 ventricle, usually swells out into 
 . a cavity furnished with muscular 
 
 walls, termed the bulbus arteri- 
 OSUS. Its use is to assist the 
 ventricle in propelling the blood 
 to the gills. Instead of passing 
 immediately to the heart, as in 
 the other Yertebrata, the aerated 
 blood is conveyed from the gills 
 through the system, and is 
 changed into venous blood be- 
 fore it again reaches the auricle. 
 
 The blood is generally of the 
 same temperature as the water 
 in which the fish lives. The 
 majority of the corpuscles are red 
 (except in the lancelet), oval, and 
 nucleated. 
 
 64. Respiration. All fishes 
 are furnished with an apparatus 
 termed gills, adapted for breath- 
 er, system of veins, conveying ing the air contained in water. 
 
 the blood to the heart; &, auri- qrL~ fxil^^ A e J.T, 
 
 cle; c, ventricle; d, branchial llie tollOWlXlg description of the 
 
 artery, corresponding to the structure and the arrangements 
 
 pulmonary artery of the higher ,-, .,, ,. 
 
 vertebrates; h, aorta, convey- OI the gills applies Only to the 
 
 Fia. 10. CIRCULATION OF A 
 FISH. 
 
 fishes - In the 
 
 ous fishes the arrangements are 
 considerably modified. The gills consist of cartilagin- 
 ous leaflets arranged either in single or double rows, 
 covered with a mucous membrane which is abundantly 
 supplied with minute blood-vessels. These leaflets are 
 supported on bony or cartilaginous arches which are 
 separated from one another by slits, and are connected 
 with the hyoid or tongue bone. The arches are situ- 
 ated in cavities on each side of the neck, termed the 
 "branchial chambers." The fish takes a quantity of 
 
VERTEBRATA PISCES. 63 
 
 water into its mouth by a process allied to swallowing. 
 This water is driven from the pharynx, through the slits, 
 into the gill chambers, and having passed over the gills, 
 escapes by apertures at each side of the neck, called the 
 " gill slits." These gill slits are closed in front by the 
 operculum (Lat. operculum, a lid) or gill cover. The 
 blood contained in the mumerous vessels with which 
 the gills are supplied, is aerated by the oxygen of the air 
 contained in the water which thus passes over them. 
 
 Most fish are furnished with a sac filled with gas, called 
 the " swim bladder." It lies between the alimentary 
 canal and the kidneys. Its probable use is to enable the 
 fish to maintain the proper specific gravity. In the mud- 
 fish it opens into the gullet by a tube, and seems to have 
 some analogy to the lungs of the higher vertebrates. 
 
 65. Nervous System and Senses. The brain of fishes is 
 very small compared with the spinal cord. It consists of 
 a series of lobes or ganglia connected by nerve fibres. 
 There are one or two nostrils, to which water is ad- 
 mitted, but the nasal sacs are closed behind, and, except 
 in the lepidosiren or mud-fish, do not communicate with 
 the pharynx as in the higher Yertebrata. The organs of 
 hearing consist of two cavities placed on the side of the 
 head filled with fluid, and containing each two otolithes 
 (Gr. OILS, otosj an ear; lithos, a stone). There is no 
 external ear. 
 
 66. Covering. Fishes are covered with scales, which 
 usually overlap one another, like the slates on the roof of 
 a house. These scales are of four different kinds : 
 
 1. Cycloid (Gr. Jeuklos, a circle; eidos, form). These 
 are thin, smooth, and horny, and are either circular or 
 oval in shape. Most of our common fishes have cycloid 
 scales. 
 
 2. Ctenoid (Gr. kteis, ktenos, a comb ; eidos, form). 
 These are also thin and horny, but their hinder edges are 
 fringed with comb-like spines. The scales of the perch 
 are ctenoid. 
 
 3. Ganoid (Gr. ganos, splendour; eidos, form). 
 
54 
 
 ^OOLOGY. 
 
 Ganoid scales consist of a layer of bone covered with 
 
 a coating of enamel. They are thicker and larger than 
 
 the other kinds of scales. They are generally rectan- 
 
 gular in form, and instead of 
 
 overlapping, are in contact at 
 
 the edges, like tiles in a floor. 
 
 Few living fishes have ganoid 
 
 scales, but they are character- 
 
 istic of fossil fish, especially 
 
 those found in the primary 
 
 rocks. The sturgeon is a 
 
 modern example. 
 
 4. Placoid (Gr. plax, a 
 plate ; eidos, form). These 
 scales consist of bony grains 
 or plates scattered over the 
 surface of the skin. The plates 
 are sometimes furnished with 
 
 ipiifp ctninpQ Thpv arp ffvnnrl 
 acuie spines. J.ney a e lounu 
 
 111 the sharks and. rays. 
 
 67. Development. Fish are generally oviparous ani- 
 mals. The ovaries, which are known by the name of roe> 
 are of large size, and sometimes contain an immense 
 number of ova. The male organs are called "milt" or 
 soft roe. The ova, after deposition in the water, are 
 impregnated by the milt. 
 
 Some fish are ovoviviparous. 
 
 FIG. 20. FISH SCALES. 
 
 c cycloid scale of the carp; a, 
 ctenoid scale o the perch . d 
 
 ganoid scales; e, placoid scale. 
 
 QUESTIONS. II. 
 
 1. What is the derivation of Mammalia ? 
 
 2. What are the most important characters of this class ? 
 -3. What are the principal regions of the vertebral column ? 
 
 4. What is the general number of the cervical vertebra, and 
 
 what are the exceptions ? 
 
 5. How many dorsal vertebrae are there ? 
 
 6. How is the cavity of the chest formed ? 
 
 7. What is the sternum ? 
 
 8. Where are the lumbar and sacral vertebrse situated 
 .9. What is meant by " anchylosed " ? 
 
QUESTIONS. 55 
 
 10. What are the caudal vertebrae? 
 
 11. What mammals have less than two pairs of limbs ? 
 
 12. Name, in their order, the various bones of the fore-limb. 
 
 13. How is the fore-limb joined to the trunk ? 
 
 14. What are the scapulce ? 
 
 15. What are the clavicles ? 
 
 16. Name, in their order, the bones of the hind-limb. 
 
 17. Describe the teeth of a typical mammal. 
 
 18. What mammals are destitute of teeth ? 
 
 19. How many sets of teeth may a mammal have ? 
 
 20. What is saliva, and how is it produced? 
 
 21. What is the gastric juice, and where is it formed? 
 
 22. What is chyme ? 
 
 23. How is it changed into chyle ? 
 
 24. What is the source of the blood ? 
 
 25. Describe the heart and circulatory organs in the Mammalia. 
 
 26. What is the peculiarity of the red blood-corpuscles in this 
 
 class ? 
 
 27. Describe the process of respiration in mammals. 
 
 28. How do the lungs of mammals differ from those of birds ? 
 
 29. What are bronchi ? 
 
 30. What is the pleura ? 
 
 31. Describe the mammalian brain. 
 
 32. What is the corpus callosum ? 
 
 33. How are mammals covered ? 
 
 34. What members of this group are without hair ? 
 
 35. How is hair modified in the porcupines and hedgehogs ? 
 
 36. Into what sub-classes have the Mammalia been divided ? 
 
 37. What is the placenta, and what mammals are destitute of 
 
 this structure ? 
 
 38. What are the Sauropslda ? 
 
 39. What characters are common to birds and reptiles ? 
 
 40. How has the skeleton of birds been adapted for flight ? 
 
 41. What are the distinctive features of the skull in this class ? 
 
 42. Describe the cervical region of the spine. 
 
 43. The dorsal region. 
 
 44. Why are the dorsal vertebrae usually anchylosed ? 
 
 45. What is the " plough-share " bone ? 
 
 46. How did the Arcliwopteryx differ from ordinary birds ? 
 
 47. What is the peculiarity of the sternum ? 
 
 48. What is its form in birds which do not fly? 
 
 49. Describe the " pectoral arch." 
 
 50. What is the " merry- thought " ? 
 
 51. What is the structure of the "fore-limb"? 
 
 52. What is the structure of the " hind-limb " ? 
 
 53. Describe the " tarso-metatarsus." 
 
 54. How many toes have birds, and how are they arranged ? 
 
56 ZOOLOGY. 
 
 55. What birds have more, and what have less, than four toes ? 
 
 56. What is the nature of the beak ? 
 
 57. Describe the digestive apparatus in birds. 
 
 58. How does the gizzard differ in grain-eating and flesh-eating 
 
 birds? 
 
 59. What is the cloaca f 
 
 60. Compare the temperature of birds with that of mammals. 
 
 61. How is the high temperature accounted for ? 
 
 62. Describe the circulation in this class. 
 
 63. How does the heart of a bird differ from that of a mammal ? 
 
 64. What are the peculiar features of the respiratory process in 
 
 birds ? 
 
 65. What are "pneumatic" bones? 
 
 66. What are the distinctive features of the brain in birds ? 
 
 67. Give the peculiar characters of the eye and ear. 
 
 68. Describe a feather. 
 
 69. How do ostrich feathers differ from those of ordinary birds ? 
 
 70. What is "incubation"? 
 
 71. How are the Autophagi distinguished from the JffeteropJiagl ? 
 
 72. Give examples of the class Reptilia. 
 
 73. What characters are common to reptiles and birds ? 
 
 74. How do reptiles differ from birds ? 
 
 75. What reptiles are destitute of limbs ? 
 
 76. What reptiles have no teeth ? 
 
 77. How do the teeth of reptiles differ from those of mammals ? 
 
 78. How do the teeth of crocodiles differ from those of other 
 
 reptiles ? 
 
 79. Describe the structure of the heart and the circulation in 
 
 reptiles. 
 
 80. How does the heart of a crocodile differ from the heart of 
 
 other reptiles ? 
 
 81. How does the venous blood become mixed with the arterial 
 
 blood in the crocodile ? 
 
 82. Describe the covering of reptiles. 
 
 83. What is meant by ovoviviparous ? 
 
 84 Define the class Amphibia, and mention some examples of this 
 class. 
 
 85. How do these animals resemble, and how do they differ 
 
 from fishes ? 
 
 86. Describe the skull, fore-limb, and hind-limb of an amphibian. 
 
 87. Describe the process of respiration in the larval and adult 
 
 states respectively. 
 
 88. What is the structure of the heart, and the nature of the 
 
 circulation in this class ? 
 
 89. Describe the metamorphosis of the common frog. 
 
 90. How does a newt differ from a frog ? 
 
 91. Define the class Pisces, and give examples. 
 
QUESTIONS. 57 
 
 92. In what respects do fishes resemble, and how do they differ 
 
 from the Amphibia ? 
 
 93. What is the nature of the skeleton in fishes ? 
 
 94. What is meant by "amphiccelus" ? 
 
 95. What is the nature of the limbs in fishes ? 
 
 96. What are "fins"? 
 
 97. How are the "median" fins distinguished from "paired" 
 
 fins? 
 
 98. What pairs of fins correspond respectively to the legs and 
 
 arms of a man ? 
 
 99. By what names are the median fins which surround the body 
 
 known? 
 
 100. What are " interspinous bones" ? 
 
 101. What is the distinction between a "heterocercal" and a 
 
 " homocercal" tail ? 
 
 102. How does the tail of a fish differ from that of a whale ? 
 
 103. Describe the digestive apparatus in fishes. 
 
 104. What are " pyloric caeca" ? 
 
 105. Describe the heart, and the course of the circulation in 
 
 fishes. 
 
 106. What is the " bulbus arteriosus" ? 
 
 107. Describe the process of respiration in fishes. 
 
 108. How do gills differ from lungs ? 
 
 109. What is the " operculum " of a fish ? 
 
 110. What is the nature and use of the " swim bladder " ? 
 
 111. Describe the brain of a fish. 
 
 112. How do the nostrils differ from those of other vertebrates ? 
 
 113. Describe the organs of hearing in this class. 
 
 114. What is the nature of the covering of fishes ? 
 
 115. What are the different forms of fish scales ? 
 
 116. What is the " roe," and what is the " milt" ? 
 
 117. How does the lancelet differ from ordinary fishes ? 
 
 118. What are the peculiar features of the lepidosiren ormud-fish? 
 
58 ZOOLOGY 
 
 CHAPTEE III. 
 ANNULOSA AND ANNULOIDA. 
 
 SUB-KINGDOM II. Annulosa. 
 
 DIVISION I. Arthropoda, 
 
 CLASS 1. Insecta. 
 
 68. The highest class of Arthropoda is termed Insecta 
 (Lat. inseco, I cut into). It is so called on account of 
 the deep grooves which usually separate the bodies of 
 these animals into three distinct parts. 
 
 69. Definition. Insects are distinguished from the 
 other classes of Arthropoda by the following peculiarities 
 of structure : There are three distinct sections in the 
 body head, thorax, and abdomen; the perfect animal 
 has three, pairs of legs attached to the thorax, which 
 also bears one or two pairs of wings. The abdomen is always 
 without limbs. There is one pair of antennae. Kespiratioii 
 is performed by means of air tubes or tracheae. 
 
 70. Skeleton. As in the Annulosa generally, the hard 
 parts of insects are external. The body is covered by 
 an integument which is hardened by a horny substance, 
 termed chitine (Gr. chiton, a coat). To this exoskeleton, 
 which covers both body and limbs, the muscles are at- 
 tached. There are never more tljan twenty ringed seg- 
 ments, or somites (Gr. soma, body), in the body. Five 
 or six of these somites form the head, and three the 
 thorax. There are usually eight or nine somites in the 
 abdomen. The somites of the head are so completely 
 amalgamated as to form a single piece. The segments of 
 the thorax are also amalgamated, but not so as to be un- 
 distinguishable. The segments of the abdomen are 
 movable upon one another. 
 
ANNULOSA INSECTA. 
 
 59 
 
 The head bears a pair of jointed antenn93 (Lat antenna, 
 the yard-arm of a ship). These have-been considered by- 
 some naturalists 
 organs of smell; 
 by others, organs 
 of touch; others 
 again suppose 
 them to be or- 
 gans of hear- 
 ing. 
 
 Each joint of , 
 the thorax bears 
 a pair of limbs. 
 There are from 
 six to nine joints 
 in each limb. 
 The foot or tarsus , 
 has several j oints. 
 It is followed 
 successively by 
 the " shank," 
 " thigh," and 
 " hip " joints. 
 The foot is 
 usually terminated by two hooks. 
 
 There are generally two pairs of wings attached to the 
 dorsal surfaces of the second and third segments of the 
 thorax. The wings consi st of " a h ighly elastic m embrane, 
 stretched over a frame-work of strong tubes, as the silk 
 of an umbrella is expanded over its ribs." (Gosse.) The 
 front pair of wings in the beetles are hardened by chitine, 
 and form coverings for the protection of the membranous 
 pair. The extremity of the abdomen is furnished with 
 organs, which are sometimes used as weapons of offence 
 and defence, as the sting in bees and wasps ; and some- 
 times as "ovipositors," which serve for placing the eggs 
 in the required position. This ovipositor is a very com- 
 plex organ. It consists of a number of bristles enclosed 
 
 FIG 21.- DIAGRAM or AN INSECT, 
 
 "With the division of its body into head, thorax, and 
 
 abdomen. 
 
60 
 
 ZOOLOGY. 
 
 in a sheath, the whole forming a tube through which the 
 egg passes to its destination. In the working bees and 
 wasps a similar tube forms the " sting," which not only 
 makes a wound, but inserts poison therein. 
 
 Other insects are furnished with bristles at the ex- 
 tremity of the body. These, in the spring-tails, assist in 
 leaping. 
 
 71. Digestion. 
 Some insects, such 
 as the beetles, mas- 
 ticate their food ; 
 others, like the but- 
 terflies, subsist by 
 suction. The or- 
 gans of the mouth 
 are varied to suit 
 these different func- 
 tions. In a beetle 
 there are two lips, 
 an upper (labrum) 
 and a lower (labi- 
 UHl), closing the 
 mouth above and 
 below ; and two 
 pairs of hooked and 
 toothed jaws, which 
 work horizontally. 
 The upper jaws are 
 termed mandibles. 
 
 a, head and mouth ; &, salivary glands ; c, ceso- -j i 
 
 phagus ; e, crop ; h, stomach ; k, Malphigian ana are 
 canals representing the liver ; I, poison gland, biting j the lower 
 
 are called maxillae, their office being to masticate the 
 food. 
 
 The lower lip, which is believed to consist of a second 
 pair of maxillse united together, and the lower pair of 
 jaws, bear each one or two jointed filaments termed palpi 
 (Lat. palpOy I touch), which are supposed to be organs of 
 touch. 
 
 Fig. 22. DIGESTIVE APPARATUS AND POISON 
 GLAND OF THE BEE. 
 
AXNULOSA INSECTA. 
 
 61 
 
 In the butterflies, the upper lip and mandibles are un- 
 developed; the maxillse are very long, and form, by their 
 coalescence, a suctorial tube, 
 which is coiled up under the 
 head when not employed in 
 sucking the juices of flowers. 
 When coiled up, the tube is sur- 
 rounded by the labial palpi, 
 which, in these insects, take 
 the form of two hairy cushions. 
 
 The mouth, in the bee, is 
 adapted both for biting and 
 suction. The labrum and man- 
 dibles are of the ordinary form, 
 and are employed in the manu- 
 facture of the honeycomb. The 
 maxillae and the labium are con- 
 verted into a long tube, which 
 is used in sucking the honey 
 which forms the food of these 
 insects. This tube cannot be 
 coiled up as in the butterflies. 
 
 In the bugs and plant lice 
 the jaws are transformed into 
 lancets. These are enclosed in 
 the labium, which takes the 
 form of a tubular sheath. In 
 the flies (Dipt era) the jaws 
 sometimes take the form of 
 bristles, and sometimes 
 lancets. 
 
 The mouth leads by an oesophagus into a membranous 
 and generally folded stomach, termed the crop. From 
 this, in the masticating insects, it 'passes into a second 
 stomach, called the gizzard, which is furnished with 
 muscular walls and plates of chitine, for grinding the food. 
 Then follows the true digestive stomach, which is suc- 
 ceeded by an intestine of variable length, being short in 
 
 FIG. 23. DIGESTIVE APPARATUS OP 
 
 THE CRICKET. 
 
 a, head and its appendages ; &c, 
 salivary glands ; d, antennae ; e, 
 gizzard, preceded by the O3sophagus 
 bearing the crop ; /, sacs connected 
 with the gizzard; gh, true diges- 
 tive stomach ; i, intestine ; k, Mal- 
 0f phigian canals. 
 
62 
 
 ZOOLOGY. 
 
 suctorial insects, and long in those that feed on vegetables. 
 
 The intestine ends in a 
 cloaca, which also receives 
 the products of the genital 
 organs. 
 
 The oesophagus is usu- 
 ally furnished with tubular 
 organs, which are believed 
 to be salivary glands. 
 There are certain other 
 tubes connected with the 
 intestine which are thought 
 to be the representa- 
 tives of the liver and 
 kidneys. 
 
 72. Circulation. The 
 heart of insects is in the 
 form of a long tube. It 
 is placed along the back, 
 and, on this account, is 
 called the " dorsal vessel." 
 It consists of eight or nine 
 sacs opening into one an- 
 other, and connected by ; 
 valves which allow the 
 blood to pass towards the 
 head, but not in the oppo- 
 site direction. The blood 
 received into the heart is 
 driven for wards by the con- 
 traction of these sacs, until 
 it escapes near the head. As there are neither veins 
 nor arteries, the blood is conveyed back to the heart 
 through the interstices of the tissues. 
 
 73. Respiration is effected by a series of branched 
 tubes called tracheSB (Gr. trackeia, the windpipe), which 
 convey air through every part of the body. They com- 
 municate with the atmosphere by a number of slits, 
 
 Fro. 24. RESPIRATORY ORGANS OF AN 
 INSECT. 
 
 Distribution of the tracheae in the 
 thorax and abdomen of the Nepas. Stig- 
 mata and air sacs. 
 
ANNULOSA INSECTA. 
 
 63 
 
 called stigmata (Gr. stigma, a mark), placed on both 
 sides of the segments of the thorax and abdomen. 
 There are seldom more than nine pairs 
 of stigmata. The membranous walls of 
 the tracheae are kept distended by an 
 elastic, chitinous thread which is coiled 
 up within them in a spiral form. The 
 blood in its passage through the tissues 
 is purified by the oxygen of the air con- 
 veyed by the tracheae. 
 
 74. Nervous System and Senses. Tho 
 nervous system in the Insecta bears a 
 general resemblance to the form usually 
 found in the Annulosa. It consists of a 
 chain of ganglia, connected by a double ner- 
 vous cord, occupying the ventral position of 
 the body, and crossed in front by the gullet. 
 The ganglia placed above the oesophagus, 
 called the cephalic (Gr. cephale, the head) 
 ganglia, or " brain," furnish nerves to the 
 
 eyes and antennae. The eranglia below m Fl - 25. SPIRAL 
 , , ,, . THREAD OF THE 
 
 tne oesophagus supply nerves to the legs TRACHEA OF AN 
 and wings. INSECT. 
 
 75. The eyes are usually compound, consisting often of 
 many thousand hexagonal lenses. " They are formed by 
 a large number of eye tubes closely pressed together, so 
 that each of them has become hexagonal." (Haughton.) 
 Each of these lenses is supplied with a nervous filament. 
 There are usually simple eyes in addition to the compound 
 eyes; and, in a few cases, these alone are present. These 
 simple eyes consist of single hexagonal lenses. The only 
 other organs of sense are the antennae, which have 
 already been described. 
 
 76. Development. Insects are oviparous animals, and 
 have the sexes distinct. The animal emerging from the 
 egg has generally a very different form from that which 
 it finally assumes. The changes which they undergo are 
 tc-vmcd metamorphosis (Gr. meta, change; morphe, 
 
64 ZOOLOGY, ' 
 
 form). Some insects have a threefold metamorphosis; 
 in others, the transformation is incomplete, and a few 
 appear to remain unchanged. They 
 have, accordingly, been divided into 
 three sections, corresponding with the 
 degree of transformation which they 
 pass through : 
 
 1. Holometabolic (Gr. holos, whole; 
 metabole, change) insects. These pass 
 through three stages in progressing 
 from the egg to the perfect insect. 
 The first stage is termed the larva or 
 caterpillar. In this state, the insect 
 resembles a worm, and generally has 
 numerous legs. It eats voraciously; 
 and, as it increases in size, often changes 
 its skin, acquiring a new covering of 
 FIG. 26. NERVOUS SYSTEM larger size as often as it does so. It 
 OF THE BEE. then passes into a quiescent state in 
 
 which it is termed a pupa (Lat. pupa, a doll) or chrysalis. 
 Sometimes the pupa is covered with a " cocoon," spun by 
 the larva; in other cases it is enclosed in a chitinous 
 skin. While in this state, the legs, wings, and other 
 organs are developed ; and at length, the perfect insect, or 
 imago, emerges from its prison. Beetles, butterflies, 
 moths, &c., belong to this group. 
 
 2. Hemimetabolic (Gr. hemi, half; metabole, change) 
 insects also undergo three stages of transformation. The 
 larva, however, differs little from the imago, except in its 
 being wingless, and of smaller size. The pupa is some- 
 what larger than the larva, and possesses rudimentary 
 wings in the form of thick lobes, enclosed in cases. The 
 pupa is active, instead of being quiescent, as in the 
 holometabolic insects. Ultimately the wings are de- 
 veloped, and it then becomes the imago or perfect insect. 
 This kind of metamorphosis is termed incomplete. 
 
 Grasshoppers, crickets, dragon-flies, &c., belong to this 
 group. The larva and pupa of the dragon-fly live in water. 
 
AXXULOSA MYRIAPODA. 65 
 
 3. Ametabolic (Or. a, without; melabole, change) 
 insects undergo no metamorphosis. The adult insect does 
 not differ from the young, except in point of size. These 
 insects never acquire wings. 
 
 CLASS 2. Myriapoda. 
 
 77. The Myriapoda (Gr.murios, ten thousand ;poda, feet) 
 is a very small class, comprising only the centipedes and 
 millipedes. These animals in many respects resemble the 
 insects, and are often included in that class. They differ 
 from the Insecta, however, in the following characters : 
 The head is distinct, but there is no marked line of 
 separation between the thorax and abdomen. There are 
 always more than twenty somites in the body. The 
 limbs are numerous, and are attached to the segments of 
 the abdomen as well as to the thorax. The eyes are 
 simple. Wings are never present. 
 
 78. Skeleton. The myriapoda are provided with an in- 
 tegument hardened by chitine, as in the Insecta. This 
 integument is divided into somites, of which there are 
 always more than twenty. The head is always distinct, 
 but there is no marked line of division between the thorax 
 and abdomen. The head consists of five or six amal- 
 gamated somites. All the other segments of the body, 
 except the last, are exactly like one another. The limbs, 
 as the name of the class implies, are numerous, and are 
 borne by the somites that correspond to the abdomen in 
 the Insecta and Arachnida, as well as by those of the 
 thorax. Each segment bears one pair of limbs. In one 
 group, there are apparently two pairs of limbs attached to 
 each segment. It seems, however, in these cases, that 
 what appears to be a single segment, really consists of two 
 somites amalgamated together. The appendages of the 
 anterior segments are often modified into organs of 
 prehension. 
 
 79. The internal organs of the myriapoda bear a close 
 resemblance to those of the Insecta. There is a dorsal 
 
 15 E, E 
 
66 
 
 ZOOLOGY 
 
 vessel divided into sacs by valvular partitions, conveying 
 the blood towards the head. .Air is conveyed through 
 
 FIG. 27. CENTIPEDE. 
 
 a, centipede ; b, anterior part of the body seen from above ; c, eyes of the 
 right side magnified ; d, head ; e, antenna ; /, anterior part of scolopendra, 
 .seen from below ; g, perforated hooked jaws ; h, posterior part of the body ; i, 
 the same seen from below ; k, one of the somites with foot and stigma ; lc' I, 
 isolated stigmata ; m, antenna of Geophiius. 
 
 the body by tracheae which communicate with the atmos- 
 phere by stigmata. In those groups which have one pair 
 of limbs attached to each segment, the stigmata occur on 
 the sides of every alternate somite; but when the segments 
 bear two pairs of limbs, each is furnished with a pair of 
 breathing apertures. This seems to corroborate tho 
 opinion, that in these cases, each segment consists of two 
 amalgamated somites. 
 
 80. The nervous system is similar to that found in 
 
ANNULOSA ARACHNIDA. 67 
 
 the Insecta. There is one pair of antennae attached to 
 the head. The eyes are simple, and vary in number. 
 
 81. Development. The young animal, on emerging from 
 the egg, differs little from the adult, except that it has a 
 smaller number of segments and limbs. At each change 
 of skin it increases in size. Some of them, at first, are 
 quite destitute of feet; others are furnished with three 
 pairs, like the insects. 
 
 CLASS 3. Arachnida. 
 
 82. The class Arachnida (Gr. amchne, a spider) comprises 
 the spiders, scorpions, and mites. The head and thorax 
 are united, forming a mass termed the cephalothorax. 
 The abdomen is distinct. The antenna are converted 
 into a pair of mandibles or prehensile jaws. There are 
 four pairs of limbs, borne by the cephalothorax. The 
 abdomen is destitute of legs. Respiration is effected 
 either by tracheae or pulmonary sacs. 
 
 83. Skeleton. The integument is usually hardened by 
 chitine, but is sometimes soft and elastic. In the higher 
 groups, the body is composed of twenty somites, six of 
 which form the head. The segments of the thorax are 
 amalgamated with those of the head, forming what is 
 termed the cephalothorax. There are four pairs of limbs 
 attached to the cephalothorax. The joints of the limbs 
 are similar to those of the insects. Each limb is furnished 
 with two claws at its extremity. The abdomen in the 
 spiders is unsegmented; but in the scorpions it consists of 
 a long, flexible, jointed tail. It is always destitute of 
 legs. 
 
 The abdomen in the scorpions is terminated by a 
 hooked claw, which is its principal weapon. This claw 
 is perforated, and communicates with a poison gland 
 situated at its base. 
 
 There are glands, situated in the abdomen of the spiders, 
 which secrete a glutinous substance that has the property 
 of hardening when exposed to the air. These glands 
 
68 ZOOLOGY. 
 
 communicate with four or six small teat-like organs, 
 called spinnerets, placed at the extremity of the body, 
 each of which contains a great number of minute tubes. 
 Through each of these a slender thread of this sticky 
 substance is drawn. The animal, by means of the claws 
 of its hind feet, unites all these filaments together. The 
 spider's thread is thus, small as it is, a rope composed of 
 thousands of strands. 
 
 84. Digestion. The mouth, which is situated in the 
 front of the cephalothorax, is furnished with a pair of man- 
 dibles, which are believed to be the representatives of the 
 antennae of the other Arthropoda, a pair of maxillae, and 
 a labium or lower lip. In the scorpions there is also a 
 labrum or upper lip. In the spiders, the mandibles are 
 each provided with a perforated hooked joint, which 
 conveys poison from a gland at its base. By means of 
 this poison, the spiders are able to kill the insects, on the 
 juices of which they subsist. The mandibles of the 
 scorpions are terminated by pincers. The maxillae are 
 each provided with long jointed appendages, termed 
 palpi. In the female spiders, these are terminated by 
 claws; in the males, by sexual organs. The maxillary 
 palpi of the scorpions are very long, and are furnished 
 with grasping claws. As the food of the spiders consists 
 merely of the juices of those animals on which they 
 subsist, their alimentary apparatus is extremely simple. 
 The intestine is short, and without convolutions. There 
 are salivary glands, and tubes which are believed to 
 represent kidneys. 
 
 85. Circulation. There is usually a heart, similar to 
 the " dorsal vessel " of the Insecta and Myriapoda. Some 
 of the lower groups are without any special blood-vessels. 
 
 86. Respiration is performed variously in the different 
 groups. All, however, breathe air directly. Some groups 
 have tracheae, like those found in the Insecta and Myria- 
 poda ; others have a modified form of these, consisting of 
 a series of bags along the sides of the animal, formed by 
 &n in volution of the integument^ and qpnimunicating \yitli 
 
ANNULOSA ARACHNIDA. 
 
 the atmosphere by stigmata. The walls of these bags, 
 which are termed pulmonary sacs, are abundantly 
 supplied with blood- 
 vessels. Sometimes 
 there are both tracheae 
 and pulmonary sacs. 
 In the lowest groups 
 there are no special 
 breathing organs, the 
 blood being aerated 
 by the general sur- 
 face of the body. 
 
 87. The Nervous 
 System consists of 
 the usual chain of 
 ganglia, but is more 
 condensed than in the 
 Insecta. There is a 
 cephalic ganglion 
 above the 03sophagus, 
 and a large ganglion 
 placed in the thorax. 
 There is sometimes 
 also a small ganglion 
 in the abdomen. 
 These ganglia are 
 united by a pair of 
 filaments, and give 
 off nerves to the 
 various organs of the 
 body. 
 
 88. The eyes, 
 which are always 
 
 simple, are placed in the front of the cephalothorax. 
 They vary in number from two to eight. 
 
 89. Development. The Arachnida are generally ovi- 
 parous, and, with some exceptions, unisexual. In most 
 cases, the young animal resembles its parent in every- 
 
 FIG. 28. ANATOMY OF SCORPION*. 
 a, the dorsal vessel and arteries ; &, alimen- 
 tary canal ; b' , anus ; c, chain of nervous ganglia ; 
 e' , one of the eyes and its optic nerve ; dd, pul- 
 monary sacs; c, terminal hooked claw with 
 poison gland. 
 
70 
 
 ZOOLOGY. 
 
 thing except size. Tlie mites, however, have but three 
 pairs of legs in the larval state, and only obtain the 
 additional pair after casting the skin several times. 
 
 90. Divisions. The Arachnida may be divided into 
 two sub -classes : 
 
 1. Pulmonaria. These breathe by pulmonary sacs, and 
 sometimes by tracheae also. They have six or eight 
 simple eyes. The scorpions and most spiders belong to 
 this sub-class. 
 
 2. Trachearia. The members of this group breathe 
 either by tracheae or by the general surface of the body. 
 They have never more than four simple eyes. This sub- 
 class includes the cheese-mite, itch-insect, and harvest- 
 spider. 
 
 CLASS 4. Crustacea. 
 
 91. The class Crustacea (Lat. crusta, a crust) is so called, 
 because the body is often covered by a skin which con- 
 tains a considerable quantity of carbonate of lime, and 
 is hardened into a shell or crust. This skin forms the 
 external skeleton, and within it all the soft parts of the 
 body are inclosed. The Crustacea is a very large class, 
 including lobsters, crabs, shrimps, prawns, barnacles, sea 
 acorns, &c., groups of animals that differ widely in ap- 
 pearance and structure. It is closely allied to the 
 Arachnida ; but may be distinguished from it and 
 the other classes of Arthropoda by the following 
 characters : When breathing organs are present, they 
 always take the form of gills or branchiae, which adapt 
 them for respiring air in water ; they have always more 
 than four pairs of limbs (the usual number being five or 
 seven pairs), which are not confined to the thorax, but are 
 usually attached to the abdomen also ; one or more of 
 these pairs of limbs are usually modified into masticating 
 jaws ; there are two pairs of antennae ; they undergo 
 metamorphosis before arriving at maturity. 
 
 92. Skeleton. The body is usually divided into three 
 
ANNULOSA CRUSTACEA. 7 1 
 
 regions head, thorax, and abdomen. In a typical speci- 
 men, it is composed of twenty-one somites. Seven of these 
 are assigned to the head, thorax, and abdomen, respectively. 
 The segments of the head and thorax are usually united 
 into a single mass, termed the cephalo thorax. The 
 skeleton is so varied, that no general description can be 
 given, which will apply to all the groups. The lobster 
 may be selected as a representative of the class. In this 
 animal the body is divided into two regions, which are 
 popularly termed the head and tail. The so-called 
 "head" is the cephalothorax, which is covered by a 
 large plate termed the carapace. The "tail" is the 
 abdomen, the joints of which are movable upon one 
 another. To the first segment of the head are attached 
 movable stalks which bear a pair of compound eyes. 
 The next two segments bear two pairs of antennae, called 
 respectively the antennules, and the great antennae. 
 The appendages of the mouth follow, and are of a very 
 complex character. There is a labrum or upper lip, a 
 labium or lower lip, a pair of biting jaws or mandibles, 
 and two pairs of maxilloB. One of these is furnished 
 with a spoon-like organ which is used in causing a 
 current of water to flow through the gill chamber. The 
 maxillse are followed by three pairs of maxillipedes, or 
 foot-jaws, one of which is attached to the last segment 
 of the head, the others to the first two segments of the 
 thorax. The maxillipedes are modified limbs, used as 
 masticating organs. The remaining five segments of the 
 thorax bear five pairs of walking legs. The first three 
 pairs are furnished at their extremities with nipping 
 claws. The front pair are much larger than the others, 
 and are termed the great claws. The two remaining pairs 
 of legs terminate in a single point, being without pincers. 
 To each of the segments of the abdomen, except the 
 last, paddle-like organs, called swimmerets, are attached. 
 The segment at the extremity of the body is termed the 
 telson (Gr. telson, a boundary), and is destitute of ap- 
 pendages. 
 
72 
 
 ZOOLOGY. 
 
 93. Digestion. The alimentary canal is usually with- 
 out convolutions, running straight through the body, 
 from the mouth to the anus. 
 The oesophagus leads to a large 
 stomach, which in some cases is 
 furnished with a calcareous ap- 
 paratus for grinding the food. 
 There is generally a large liver, 
 but no salivary glands have been 
 detected. 
 
 94. Circulation. The heart, 
 when present, is placed above the 
 alimentary canal. In the higher 
 groups, it consists of a single 
 cavity, which, by its contractions, 
 drives the blood through arteries 
 to the various organs, and to the 
 gills, where it is purified by the 
 air contained in the water. There 
 being no capillaries, the blood, 
 after leaving the arteries, is con- 
 
 FIG. 29. CIRCULATION IN THE veyed through the interstices be- 
 tween the organs of the body to 
 the veins which carry it back 
 to the heart. It follows, there- 
 fore, that the heart in this class contains arterial and not 
 venous blood, as in the case of fishes. The heart in some of 
 the lower forms resembles the "dorsal vessel "of the insects. 
 95. Respiration. When the Crustacea possess distinct 
 breathing organs, they always take the form of gills, 
 adapted for obtaining the vital oxygen, not directly from 
 the atmosphere, but from the air contained in water. In 
 the higher groups, these gills are shaped like pointed 
 pyramids, which consist of a central stem, bearing a 
 great number of thin membranous plates placed closely 
 together, but yet admitting a flow of water between 
 them. These organs are abundantly supplied with blood- 
 vessels. In the lobsters they are attached to the bases 
 
 CRAY FISH. 
 aa, anterior artery and 
 
 principal divisions ; 
 ap, posterior aorta. 
 
 heart; 
 
ANNU LOS A CRUSTACEA. 7 3 
 
 of the legs, and enclosed in a cavity formed beneath 
 the carapace on each side of the body. These cavities 
 are furnished with two openings, and circulation of 
 water is kept up within them by the movements of the 
 legs. In some of the lower groups, there are no dis- 
 tinct respiratory organs. 
 
 96. The nervous system is similar to that found in 
 the Insecta. There is a pair of ganglia developed in 
 each somite. These are connected by double nervous 
 cord-5. The cephalic ganglia are placed above the 
 oesophagus, the others run along the ventral surface 
 of the body, the gullet passing between the two front 
 pairs. 
 
 The higher Crustacea possess compound eyes, similar 
 to those of the insects. They are often placed at the 
 summit of movable stalks, which are sometimes of con- 
 siderable length. In the lower forms, the eyes are 
 simple. There is often only one eye, which is placed in the 
 middle of the head. 
 
 97. The organs of hearing in the higher groups are placed 
 close to the base of the long antennae. They consist each 
 of a hollow sac which is closed externally by a thin mem- 
 brane. Behind this is a cavity filled with fluid, which 
 is connected with the auditory nerve. 
 
 98. Development. The Crustacea are oviparous animals, 
 and, except one group, are all unisexual. The eggs, 
 after exclusion, are generally carried about by the mother 
 until near the period of hatching. They are either at- 
 tached to the abdominal feet, or placed in pouches on 
 each side of the tail. The young animals are often so 
 unlike the adult, that, until the connection was observed, 
 they were believed to be of different species. The early 
 stages of the common shore-crab are thus described by 
 Gosse : " A hemispherical carapace or shell, not so big 
 as a small pin's head, sends up from its centre a long 
 pointed, curved spine, while another spine curves down- 
 wards from the front beneath the body like a beak ; the 
 eyes are without stalks; there are two pairs of jointed 
 
74 ZOOLOGY. 
 
 feet, ending in tufts of stiff bristles ; and a long jointed 
 body carried straight behind, which ends in two bundles 
 of diverging spines. Such is the grotesque character under 
 
 which our little masquer- 
 ader makes his first ap- 
 pearance on any stage. 
 After a time he drops his 
 outer garments, and as- 
 sumes a second form, wide 
 ly different from the for- 
 mer, and still sufficiently 
 remote from the ultimate 
 Fig. so. one; and it is not till the 
 
 LARVA OF CRAB MAGNIFIED. third moult that the little 
 
 creature, now grown to the size of a hemp-seed, begins to be 
 recognizable as a crab ; though even now he has several 
 stages to pass through several doffings of coats and trou- 
 sers before he is quite a proper shore-crab comme ilfaut" 
 As these animals increase in size, the skin becomes too 
 small to contain the body, and is cast off at intervals. 
 Moulting in the insects is confined to the larval state, 
 because when they reach the last stage, growth ceases; but 
 the Crustacea continue to grow long after the perfect 
 form is attained. While moulting, they retire to some 
 secluded place, as if conscious of their helpless condition. 
 
 DIVISION II. Anarthropoda. 
 CLASS 1. Annelida. 
 
 99. The Annelida (Lat. annulm, a ring) is a large class, 
 containing the leech, the earth-worm, the lob-worm, and 
 those animals which live in tubes, termed Serpul83. It 
 is distinguished from the Arthropoda mainly by the 
 absence of jointed limbs. 
 
 The Annelida are worm-like animals, covered with a, 
 soft skin. The body is divided into a series of rings or 
 segments, which are all exactly like one another, except 
 
ANNUL03A ANNELIDA. 75 
 
 the first and last. These rings are often very numerous, 
 amounting in some groups to several hundreds. A ring 
 or segment, in the higher groups, consists of two arches, 
 a dorsal and ventral; and each of these bears two pro- 
 tuberances, placed on the sides of the animal, which have 
 been called "foot tubercles.' 7 These tubercles support 
 
 A 
 
 FIG. 31. GROUP OF ANNELIBES. 
 A, Myrianida; B, Serpula; C, Lob-worm; D, Spirorbis. 
 
 bundles of bristles which surround a soft jointed filament, 
 called the cirrhus. These bristles, by pressing against 
 the ground, assist in locomotion. Jointed limbs are 
 never met with in any animal of this class, nor are the 
 organs of locomotion ever transformed into foot-jaws. 
 
 100. Digestion. There is a mouth, sometimes fur- 
 nished with horny jaws, a gullet, stomach, and intestine, 
 
76 ZOOLOGY. 
 
 which generally runs straight through the body, without 
 convolutions, until it reaches the anal opening. 
 
 101. Circulation. " No amielide ever possesses a heart 
 comparable to the heart of a crustacean or insect ; but a 
 system of vessels, with more or less extensively contractile 
 walls, containing a clear fluid, red or green in colour, 
 and, in some cases only, corpusculated, is very generally 
 developed, and sends prolongations into the respiratory 
 organs, when such exist" (Huxley). 
 
 Fig. 32. SECTION OF AN ANNELIDE. 
 
 This circulation is termed pseudo-hasmal (Gr. pseudos, 
 false ; haima, blood) ; and the vessels that contain this red 
 or green fluid are considered extreme modifications of the 
 "water vessels" of the Annuloida. There is also a cor- 
 pusculated fluid contained in the spaces surrounding the 
 internal organs (the peri visceral cavity), which is be- 
 lieved to correspond with the true blood system of the 
 Arthropoda. 
 
 102. Respiration. The breathing organs are either 
 external gills of various forms, or bladder-like sacs placed 
 on the sides of the body. " The external gills are 
 well seen in the common lug- worm, where they consist of 
 eleven pairs of arborescent organs, placed externally, and 
 rather in advance of the middle line of the body. ' ' (Haughton. ) 
 
 In some cases there are no special breathing organs, 
 respiration being effected by the surface of the body. 
 
 103. The nervous system is of the usual annulose type. 
 It consists of a double chain of ganglia running along 
 the ventral part of the body, the gullet passing between 
 
ANNULOSA CH^ETOGNATHA. 77 
 
 the two anterior pairs. The front pair are termed the 
 cerebral ganglia. 
 
 Simple eyes are possessed by most. They appear as 
 small dark spots, generally on the front of the head, but 
 sometimes on the gills. In other cases they are dis- 
 tributed over the various segments of the body. 
 
 There are usually two or more antennae which are 
 without joints. 
 
 104. Development. The sexes are sometimes distinct, 
 but the leeches and earth-worms are hermaphrodite (Gr. 
 Hermes i Mercury ; Aphrodite, Venus), that is, the sexes 
 are united in the same individual. The embryos are 
 generally furnished with vibratile cilia. 
 
 105. Divisions. This class is generally divided into 
 two groups : 
 
 1. The Branchiate section, which includes the sand- 
 worms and the serpulae. 
 
 2. The Abranchiate group, comprising the earth-worms 
 and leeches. 
 
 CLASS 2. Ch&tognatha. 
 
 106. The class Chaetognatha (Gr. chaite, hair; gnathus, 
 a jaw) consists of only a single genus, Sagitta (Lat. sagitta, 
 an arrow). These animals were formerly placed among 
 the Annelida, but, according to Professor Huxley, " they 
 are so unlike them and every other group as to require a 
 class for themselves." They are small marine animals, 
 about an inch in length, and with a transparent skin. 
 The following is an abridgment of the account of these 
 singular creatures furnished by Huxley, (see Classifica- 
 tion of Animals, p. 53): 
 
 " The head is furnished with six pairs of bristles. Two 
 of these are long and claw-like, and lie at the sides of the 
 mouth. The other four are short, and placed in front of 
 the head. The hinder part of the body is fringed by a 
 fin-like membrane (hence the name Sagitta), which 
 seems to be an expansion of the cuticle. The intestine 
 
78 ZOOLOGY. 
 
 is a simple straight tube extending from the mouth to 
 the anus." 
 
 " A single oval ganglion lies in the abdomen, and sends 
 forwards and backwards two pairs of lateral cords. The 
 anterior cords unite in front and above the mouth into a 
 hexagonal ganglion. This gives off two branches, which 
 dilate at their extremities into the spheroidal ganglia, on 
 which the darkly pigmented imperfect eye rests." 
 
 SUB-KINGDOM III. Annuloida. 
 CLASS 1. Scolecida. 
 
 107. The class Scolecida (Gr. scolex, a worm) includes the 
 intestinal-worms (entozoa), the microscopic wheel-ani- 
 malcules, the hair-worms, &c. These groups differ much 
 in external appearance, but there are some important points 
 of structure common to them all. Most of them possess 
 what is called the water vascular system, a series of 
 vessels which communicate with the exterior by one or 
 more openings on the surface of the body, their branches 
 permeating the interior. These vessels are believed to 
 perform the double functions of circulation and respiration. 
 
 No heart or true circulatory apparatus has been ob- 
 served in any of them. 
 
 108. The nervous system consists of only one or two 
 ganglia. 
 
 109. There are seven groups included in this class 
 the Eotifera (or wheel-animalcules), the Turbellaria, the 
 Trematoda (or flukes), the Tseniada (or tape-worms), tho 
 Nematoidea (or thread-worms), the Acantocephala, and 
 the Gordiaceae. 
 
 110. Rotifera (Lat. rota, a wheel fero, I carry). The 
 Kotifera are microscopic animals, commonly met with in 
 fresh water ponds, and infusions of vegetable matter, 
 which have been exposed to the sun for a few days. 
 They are very small, seldom exceeding the ^ of an 
 inch in length. Their true position in the animal 
 scale is still a matter of doubb. They were formerly 
 
ANN ULOID A SCOLECID A. 7 9 
 
 classed with the Infusoria ; but the possession of a ner- 
 vous system and a complex digestive apparatus, en- 
 title them to a much higher place 
 in the animal kingdom. Some 
 place them among the Annelida; 
 other observers consider them allied 
 to the Insecta and Crustacea. They 
 have been placed among the Sco- 
 lecida, on account of the "water 
 vascular system" which they pos- 
 sess. Their nervous system is also 
 very different from anything found 
 in the Annulosa. 
 
 The body is covered with a mem- 
 branous transparent skin, through 
 which the internal organs can be 
 accurately observed. Most are free 
 swimming; but some are attached 
 to aquatic plants, &c. The anterior 
 part of the body is furnished with 
 one or two discs surrounded by 
 cilia, which move so rapidly as 
 to produce the optical illusion of FIO. SS.-ROTIFERA. 
 rotating wheels. Early observers believed that they 
 really did rotate. The movements of these cilia, by pro- 
 ducing currents in the water, bring supplies of those still 
 more minute Infusoria on which the creatures feed. In 
 the free swimming species they also form organs of loco- 
 motion, acting like the screw of a steamer. The body is 
 shaped like a spindle or barrel. The lower extremity is 
 furnished with a tapering foot-like organ, with many 
 joints, which are capable of being sheathed one within 
 another like a telescope. The "foot" either terminates 
 in a sucking-disc, or is furnished with a pair of " toes." 
 In either case it is able to attach itself to some object 
 when it desires to become stationary. 
 
 111. Digestion. As already mentioned, these animals 
 are provided with very effective food-bringers the cilia, 
 
80 ZOOLOGY. 
 
 with which the anterior end of the body is furnished. 
 The mouth leads into a pharynx, which is furnished with 
 a series of hammer-like pieces, believed by Gosse to be the 
 representatives of the mandibles and maxillse of the 
 Insecta. The food having been crushed by these hammer- 
 like jaws, passes through a gullet into a large stomach, 
 which is succeeded by an intestine, terminating in a 
 cavity called the cloaca. 
 
 112. Circulation. Nothing corresponding to the heart 
 and circulatory organs of the Arthropoda has been discov- 
 ered in the Eotifera. There is, however, a well developed 
 water vascular system. It communicates with the ex- 
 terior by an opening leading into a cloaca, which also 
 receives the excretions from the intestine and generative 
 organs. This outlet communicates with two complex 
 tubes termed respiratory tubes, which pass along the 
 sides of the animal, and terminate near the head. No 
 true organs of respiration have been observed. 
 
 113. The nervous system consists of a single mass, situ- 
 ated in the head of the animal. This mass is of such a large 
 comparative size, that Gosse asserts, it "can only be com- 
 pared to the brain of the Vertebrata." From this ganglion 
 a pair of nervous threads proceed backwards. Such a 
 nervous system is very different from the double gan- 
 glionated chain found in the Annulosa. 
 
 A red eye of simple structure is situated upon the gan- 
 glion. 
 
 114. Development. In all the Rotifera the sexes are 
 distinct. The description given above applies only to the 
 females. The males are much smaller, and are entirely 
 without digestive or masticatory organs. They, how- 
 ever, possess the water vascular system in common with 
 the females. They live but a short time, their sole busi- 
 ness being to secrete sperm. 
 
 The females deposit ova of a large comparative size. 
 The young do not undergo metamorphosis. 
 
 115. Turbellaria (Lat. turbo, I disturb). These animals 
 their name from the currents they produce in 
 
A N > ULOIDA SCOLECIDA. 
 
 81 
 
 water, by the movements of the cilia with which their 
 bodies are furnished. The best known group are the 
 planaria (Gr. plane, wandering). They are small, flat- 
 tened animals, with soft, black, gelatinous flesh. They 
 are found in great abundance in. rivers and ponds, attached 
 to submerged plants. Other larger species belong to the 
 sea shore. The mouth is placed near the centre of the 
 body. The digestive canal has only one opening. The 
 skin is furnished with numerous cilia. There are two 
 nervous ganglia placed near the mouth, connected by a fila- 
 ment. They possess a number of rudimentary eyes, which 
 are situated on the front part of the 
 body. There is a water vascular 
 system which communicates with the 
 exterior. 
 
 The nemertes or ribbon-worms also 
 belong to this group. They are found 
 on the sea shore coiled up in knots 
 under stones, arid are sometimes ninety 
 feet long. The alimentary canal has 
 two openings. The water vascular 
 system in the adult seems to have no 
 communication with the exterior. 
 
 116. Trematoda (Gr. trema, an open- 
 ing) or flukes are internal parasites in- 
 habiting the bodies of man, sheep, birds, 
 and fishes. They are somewhat flat in 
 shape, and are furnished with one or 
 more suckers, by which they attach 
 themselves to the bodies of their victims. 
 One of these suckers leads into the 
 mouth, and is succeeded by a branched 
 alimentary canal, which has no anal 
 opening. There is also a branched 
 water vascular system, which communicates with the 
 exterior. The best known of these animals infest the gall 
 bladder or the liver of the sheep, producing the disease 
 called rot. 
 
 15 E, F 
 
82 
 
 ZOOLOGY. 
 
 117. Tseniada (Gr. talma, a ribbon) or tape-worms are 
 long ribbon-shaped worms, inhabiting the intestines of 
 man and other warm-blooded animals. There are three 
 different species found in the human intestines. The 
 most common kind has been called tsenia solium, be- 
 cause it was erroneously supposed that only one such 
 worm was ever found in the intestine at the same time. 
 The head of the tape-worm is furnished with s-uckers and 
 recurved hooks, by which it attaches itself to the intes- 
 tine of its host. This head, which is in reality the true 
 animal, has no mouth nor digestive organs, its nourish- 
 
 FIGL 35. T^NIA OR TAPE-WORM. 
 
 a, Tsenia or tape-worm ; &, head (enlarged) with hooks and suckers ; c, hooks 
 magnified ; d, joint, showing branched ovary, generative pore, and water 
 vascular canals; e t ovum; /, cystic worm (cysticercus longicollis). 
 
 ment being obtained by absorption. It is also destitute 
 of reproductive organs. The nervous system is said to 
 consist of one or two ganglia ; but there are doubts on 
 this point. There is a water vascular system, which 
 consists of two tubes placed along the sides of the body. 
 These vessels are connected by cross tubes at each joint. 
 
ANNULOIDA SCOLECIDA. 83 
 
 The whole system communicates with the exterior by an 
 aperture placed at the extremity of the last joint. 
 
 The head, by a species of budding, develops a series of 
 flattened joints, each of which contains male and female 
 organs. The joints nearest the head are always the 
 newest, the mature joints being situated at the other 
 extremity. The compound animal thus formed is often 
 several yards long. 
 
 Each segment contains a large number of ova; but 
 these are never hatched within the animal inhabited by 
 the tape-worm. The mature joints gradually break off, 
 and pass from the intestine; and the minute ova con- 
 tained therein are swallowed by some warm blooded 
 animal. In the case of the human tape-worm, the ova 
 find their way into the stomach of the pig, where they 
 are hatched. The embryo, by means of the flinty hooks 
 with which its head is furnished, makes its way through 
 the walls of the stomach, into the muscles. In this situa- 
 tion it develops at its lower extremity a bladder-like sac, 
 filled with fluid. When it abounds in the flesh of the 
 pig, the pork is said to be measled. These " measles " 
 were formerly called cystic (Gr. kustis, a bladder) worms, 
 and were bqlieved to be different animals. These cystic- 
 worms, so long as they remain in the tissues of the pig, 
 never breed tape-worms, nor develop ova, but they are 
 said to be able to multiply their own kind by budding. 
 When a quantity of measly pork is eaten, a cystic-worm 
 is sometimes transferred to the human stomach. It 
 fastens itself by its hooks and suckers to the intestine, 
 loses its bladder, and commences to develop 'joints by 
 budding, and finally produces a tape-worm. 
 
 Another species of human tape-worm is derived from 
 " measles " found in the muscles of the cow. The cystic- 
 worms found in the tissues of the mouse and rat produce 
 tape- worms in the intestines of the cat ; and the cystic- 
 worm which causes the disease called staggers in sheep, 
 when transferred to the stomach of the dog, is developed 
 into a tape-worm. 
 
84 ZOOLOGY. 
 
 118. Nematoidea (Gr. nema, thread; eidos, form). To 
 this group belong the round-worms, thread-worms, 
 vinegar eels, &c. Most of them infest the intestines of 
 warm blooded quadrupeds. The round-worm sometimes 
 attains a length of fifteen inches in the human intestine. 
 The thread -worm inhabits the large intestine. It is found 
 principally in children. The Trichina passes its early 
 stage in the muscles of the pig, and is often transferred 
 to the human stomach where it is developed. Other 
 species infest the intestines of the horse and pig. These 
 animals possess a mouth and an alimentary canal with 
 anal opening. They have also a water- vascular system. 
 A ganglionated nervous cord surrounds the gullet, from 
 which nervous threads proceed towards the extremity of 
 the body. The sexes are distinct. 
 
 There are many species of non-parasitic Nematode 
 worms found in fresh water or on the sea shore. The 
 vinegar eel is a well known specimen. 
 
 119. Acanthocephala (Gr. acantkos, thorn; cephale, the 
 head). These are formidable internal parasites, which 
 inhabit the alimentary canal of many mammals, birds, and 
 fishes ; but have not yet been found in the human in- 
 testine. They are so called on account of the recurved 
 hooks with which their proboscis or snout is surrounded. 
 By means of these they attach themselves to the mucous 
 membrane of the intestine. There is a single nervous 
 ganglion at the base of this proboscis. There is a network 
 of canals beneath the skin, containing a clear fluid, which 
 is believed to be a modified form of the water-vascular 
 system. They have neither mouth nor alimentary canal. 
 The sexes are distinct. 
 
 120. Gordiaceae (so called from the " Gordian Knot," be- 
 cause they twist their bodies into knots), or hair-worms, 
 are popularly believed to be living horse hairs. They pass 
 the early stages of their lives in the interior of insects, 
 especially grasshoppers and water-beetles. They attain 
 a length of ten or eleven inches, and then leave the body 
 of their victim to breed. They deposit theiv eggs in 
 
AXNULOIDA ECHINODERMATA. 85 
 
 Water, or in some moist place, in long chains. They 
 
 have a mouth and alimentary canal, but no anus. The 
 sexes are distinct. 
 
 CLASS 2. Echinodermata. 
 
 121. The class Echinodermata (Gr. echinos, hedgehog ; 
 derma, skin) includes the sea-urchins, star-fishes, sand- 
 stars, brittle-stars, sea-cucumbers, and the almost extinct 
 encrinites or sea-lilies, the remains of which are abun- 
 dantly met with in the older rocks. 
 
 In the mature state, the members of this class are 
 characterized by a radiate arrangement of the various 
 parts, although in the embryonic condition they have 
 bilateral symmetry. The covering is composed of numer- 
 ous calcareous plates, joined together at the edges ; or of a 
 leathery integument, in which there are calcareous grains 
 or spines. There is a water-vascular system, connected 
 with a series of tube feet, termed the ambulacral (Lat. 
 ambulacrum, a walking place) system. In all cases the 
 alimentary canal is completely shut off from the cavity of 
 the body, and is usually furnished with an anal opening. 
 A ganglionated ring of nervous matter surrounds the 
 gullet, from which branches radiate to the different parts 
 of the body. 
 
 122. Skeleton. The form of these animals varies much 
 in the different groups. The sea-urchins are sometimes 
 almost globular, the star-fishes are usually stars of five 
 rays, the sea-cucumbers (holothuria) are worm-like. The 
 covering of the sea-urchins consists of a shell or test 
 which is composed of a great number of five or six-sided 
 calcareous plates, joined together at the edges. Of these 
 plates there are ten double rows or zones. In five of these 
 zones the plates are small, and are perforated, so as to 
 allow the emission of the tube-feet. These are called the 
 
86 ZOOLOGY. 
 
 ambulacral plates. In the other five zones which 
 alternate with the ambulacral rows, the plates are larger, 
 and are not perforated. The shell is increased in size by 
 additions made to the edges of each individual plate. 
 This is effected by a delicate membrane which covers the 
 test, and dips in between the edges of the various plates, 
 adding calcareous matter to each so evenly as to preserve 
 the shape of the whole. 
 
 Besides the plates which occur in zones, or lunes, there 
 are others at the base and apex of the test. The mouth 
 is surrounded by a leathery membrane which contains a 
 number of small calcareous pieces called the oral plates ; 
 at the other extremity are similar anal plates. At the 
 apex of the test, and surrounding the anal opening, there 
 is a disc composed of a series of plates, termed the genital 
 and ocular plates. There are five genital plates, which 
 are larger in size than the ordinary plates, and pentagonal 
 in shape. Each of tliem is perforated by a duct from the 
 genital organs. One of these genital plates, larger than 
 the others, is furnished with a protuberance which con- 
 tains a large number of very minute openings. Through 
 
 FIG. 36. TEST AND JAWS OF SEA-URCHIN, WITH THE SPINES REMOVED. 
 
 these the water-vascular system communicates with the 
 exterior. The apertures are so small, that the water in 
 passing through them is freed from any particles of sand, 
 &c., with which it may be mixed. This protuberance is 
 
ANNULOIDA ECHINODERMATA. 87 
 
 called the niadreporiform tubercle, because, when examined 
 by a lens, it somewhat resembles a piece of madrepore 
 coral. The ocular plates, of which there are also five, are 
 smaller than the genital, and are placed at the extremities 
 of the ainbulacral passages. Each plate contains an open- 
 ing in which a little eye is placed. 
 
 The plates are furnished with numerous tubercles, to 
 which pines are attached by a ball-and-SOCket joint. 
 
 Fia. 37. PRINCIPAL ORGANS OF SEA-URCHIN. 
 a, oesophagus ; & e f, intestine ; g, anus ; 7i, ovary ; i, shell or test. 
 
 These spines assist in locomotion, and are also used as 
 weapons of defence. Among the spines are found a num- 
 ber of curious appendages called pedicellarijB (Lat. pedi- 
 cellus, a louse), because they were formerly believed to be 
 parasites. They are long and worm-like, and at the head 
 of each are placed three calcareous jaws, which fit together. 
 These jaws continually open and shut. Their object 
 
88 ZOOLOGY. 
 
 seems to be to drive any parrrjites away which might 
 attach themselves to the spines. 
 
 The covering in the star-fishes is leathery, but it con- 
 tains calcareous plates, with tubercles and spines. The 
 plates, however, do not unite at the edges, as in the sea- 
 urchins. 
 
 123. Digestion. The sea-urchins are vegetable feeders. 
 They are furnished with five long calcareous teeth, meet- 
 ing in a point. This structure has been termed Aris- 
 totle's lantern. The mouth, which is usually placed at 
 the base of the shell, leads to a gullet, stomach, and intes- 
 tine. This is much convoluted, winding round the inte- 
 rior of the shell. The anus is often, though not always, 
 placed in the apex. 
 
 The star-fishes are animal feeders, and subsist usually 
 on bivalve mollusks. The mouth is placed in the centre 
 of the lower surface, and is destitute of teeth. The 
 stomach is prolonged into the various rays. When there 
 is an anal opening, it is situated on the upper surface. 
 
 124. Circulation. In the sea-urchins the water -vascular 
 system communicates with the exterior by the madre- 
 poriform tubercle, situated on the largest genital plate. 
 From this tubercle proceeds a canal, which leads to a tube, 
 forming a ring round the mouth, termed the circular 
 canal. From this, five "radiating canals" proceed along 
 the ambulacral areas. These canals give off short tubes, 
 furnished with sucking discs, which are protruded through 
 apertures in the shell. They are called tube- feet, because 
 they assist in locomotion. At the base of the tube-feet 
 are situated little bladders containing water, by which 
 they are protruded or retracted at will. 
 
 Besides the water-vascular system, there is a true blood- 
 vascular system. It consists of a central, contractile 
 cavity or heart, which gives off vessels that form rings 
 round the alimentary canal, near the mouth and anus 
 respectively. From the anal ring, five arteries proceed 
 along the ambulacral zones. These communicate with 
 five vessels which run in the opposite direction, and 
 
ANNULOIDA ECHItfODERMATA. 
 
 convey tlie blood back to the heart. The details of the 
 circulation in the star-fishes are similar in all essential 
 features. 
 
 125. Respiration. There are no distinct organs of re- 
 spiration. The aeration of the blood is believed to be 
 accomplished partly by the sea water with which the peri- 
 visceral cavity is filled, and partly by the water- vascular 
 system. 
 
 Fio. 38. LARVA OF SEA-URCHIN (Enlarged 160 times). 
 
 a, mouth ; b, stomach ; c d, intestine ; e, calcareous plate ; /, ciliated organs, 
 assisting in swimming and respiration perhaps the future ambulacra! feet ; 
 09'9!.'9'"! calcareous stalks, serving as a frame-work for the body of the animal. 
 
 126. Nervous System. The gullet is surrounded by a 
 nervous cord, which connects a series of ganglia. From 
 this, filaments proceed along the ambulacral areas. 
 
 127. Development. The sexes are always distinct. 
 
90 ZOOLOGY. 
 
 One of the most remarkable features of this class consists 
 in the metamorphosis which the embryo undergoes. The 
 following eloquent description of the metamorphosis of 
 the brittle star is by Mr. Gosse : 
 
 " The first condition of every echinoderm is the same 
 an egg-like body, covered with cilia, resembling an in- 
 fusorium. Changes take place, and we presently see 
 another form assumed, which varies in some degree in 
 the different families. We lately had the pleasure of 
 finding in our dip-net several little larvae of a brittle 
 star, the first that had ever been seen in our seas ; and 
 one of these we will select for description. 
 
 " A painter's long easel affords the only object with 
 which to compare the little creature ; for it consists of 
 four long slender calcareous rods, arranged two in front 
 and two behind, with connecting pieces going across in a 
 peculiar manner, and meeting at the top in a slender 
 head. 
 
 " On this shelly, fragile, and most delicate framework, 
 as on a skeleton, are placed the soft parts of the animal, 
 a clear gelatinous flesh, forming a sort of semi-oval tunic 
 around it, from the summit to the middle, but thence 
 downwards the rods individually are merely encased in 
 the flesh without mutual connection. The interior of the 
 body displays a large cavity, into which a sort of mouth 
 ever and anon admits a gulp of water. Delicate cilia 
 cover the whole integument, and are particularly large 
 and strong on the flesh of the projecting rods. 
 
 " The appearance of this most singular animal is very 
 beautiful, its colour pellucid white, except the summit of 
 the apical knob, and the extremities of the greater rods, 
 which are rose colour. It swims in an upright position, 
 with a calm and deliberate progression. The specimens 
 which we have seen were not more than one-fortieth of 
 an inch in length. 
 
 " From this form the brittle star is developed, but in a 
 manner unparalleled in any other class of animals. The 
 exterior figure is not gradually changed, but the star is 
 
QUESTIONS. 91 
 
 constructed within a particular part of the body of the 
 larva, * like a picture upon its canvas, or a piece of em- 
 broidery upon its frame.' The plane of the future star- 
 fish is not even the plane of the larva, but one quite in- 
 dependent of and oblique to it. Strange to tell, the 
 young star does not absorb into itself the body of the 
 larva, which has acted as a nidus for it, but throws it 
 off as so much useless lumber flesh, rods, and all." 
 
 It is a remarkable circumstance in the development of 
 the Echinodermata that, while the adult forms are char- 
 acterized by " radial symmetry," the young " exhibit as 
 complete a ' bilateral symmetry' as annelids or insects." 
 
 QUESTIONS. III. 
 
 1. What is the derivation of " Insecta " ? 
 
 2. Give the definition of this class. 
 
 3. What is the nature of the skeleton ? 
 
 4. What is chitine ? 
 
 5. What is an cxoskeleton ? 
 
 6. What is a somite ? 
 
 7. How many somites are there in the skeleton of an insect, and 
 
 how many of these are assigned to each region of the body? 
 
 8. What are antcnnce, and what is supposed to be their function 
 
 in the Insecta ? 
 
 9. What are the appendages of the thorax ? 
 
 10. Describe the wings. 
 
 11. What is the peculiarity of the anterior pair of wings in the 
 
 beetles ? 
 
 12. What is the structure of the sting of a bee ? 
 
 13. What are ovipositors ? 
 
 14. Enumerate and describe the appendages of the mouth in a 
 
 typical insect ? 
 
 15. What are palpi ? 
 
 16. How are these appendages modified in butterflies and bees? 
 
 17. How are the jaws modified in the bugs and flies ? 
 
 18. Describe the digestive apparatus of a masticating insect. 
 
 19. Describe the circulatory organs in this class. 
 
 20. How does an insect breathe ? 
 
 21. What are trachea ? 
 
 22. What are stiymata ? 
 
 23. Describe the nervous system of insects, 
 
 24. What are compound eyes ? 
 
92 ZOOLOGY. 
 
 25. How do holometabolic differ from JiemimetaboUc insects ? 
 
 26. Describe the metamorphosis of each of these groups. 
 
 27. Explain the terms larva, pupa, and imago. 
 
 28. What is a cocoon ? 
 
 29. Why are the Myriapoda so called ? 
 
 30. Give the definition of this class. 
 
 31. Give examples. 
 
 32. In what respects do they differ from the Imecta ? 
 
 33. What is the nature of the metamorphosis in the Myriapoda ? 
 
 34. What animals are included in the class Arachnida ? 
 
 35. Define the Arachnida. 
 
 36. What is the cephalothorax ? 
 
 37. How do scorpions sting ? 
 
 38. What are spinnerets ? 
 
 39. Describe a spider's thread. 
 
 40. Describe the appendages of the head in the spiders and 
 
 scorpion. 
 
 41. How do spiders kill their prey ? 
 
 42. Describe the process of respiration in the Arachnida. 
 
 43. What are pulmonary sacs ? 
 
 44. What is the nature of the nervous system ? 
 
 45. Describe the organs of sight. 
 
 46. Describe the development of the Arachnida. 
 
 47. What are the principal divisions of this class, and how are 
 
 they distinguished ? 
 
 48. Define the class Crustacea. 
 
 49. Describe the exoskeleton of the lobster. 
 
 50. What is the "carapace"? 
 
 51. What is meant by the "head" and the "tail" of the lobster? 
 
 52. How many pairs of antennae have the Crustacea ? 
 
 53. What is the usual number of limbs in this class ? 
 
 54. What are swimmerets ? 
 
 55. What are "foot jaws " ? 
 
 56. What is the "telson"? 
 
 57. Describe the heart and circulatory organs of the lobster. 
 
 58. Describe the breathing organs of the lobster. 
 
 59. What is the nature of the eyes in the higher Crustacea and 
 
 in the lower groups ? 
 
 60. Describe the organ of hearing. 
 
 61. Give an account of the metamorphosis of the common shore 
 
 crab. 
 
 62. Define the Annelida, and give examples. 
 
 63. Describe the organs of locomotion possessed by some members 
 
 of this class. 
 
 64. What is the nature of the digestive organs ? 
 
 65. What is the nature of the circulatory fluid ? 
 
 66. What is meant by the " pseudo-hsemal " system? 
 
QUESTIONS. 93 
 
 67. What is the nature of the respiration ? 
 
 68. Describe the nervous system. 
 
 69. What sort of eyes do they possess ? 
 
 70. What are the principal sub-divisions of this class ? 
 
 71. Give an account of the class Chcetoynatha. 
 
 72. Define the class Scolecida. 
 
 73. What are the principal groups included in this class ? 
 
 74. Give examples of each. 
 
 75. Why are the Rotifera so called ? 
 
 76. Why have they been removed from the class Infusoria ? 
 
 77. Why have they been placed in the class Scolecida ? 
 
 78. In what respects do the males differ from the females? 
 
 79. Describe the digestive organs of the Rotifera. 
 
 80. W T hat is the nature of the nervous system in this group ? 
 
 81. Give an account of the Turbellaria. 
 
 82. Describe the Planaria. 
 
 83. Define the Trematoda, and give examples. 
 8-1. What produces the " rot" in sheep ? 
 
 85. To what group does the "tape- worm" belong? 
 
 86. What are "cystic" worms, and what relation do they sus- 
 
 tain to the tape-worms ? 
 
 87. Describe the ordinary tape-worm. 
 
 88. Give an account of the development of this animal. 
 
 89. What are the "measles" met with in diseased pork? 
 
 90. Give examples of Nematode worms. 
 
 91. How do they differ in structure from the Trematoda? 
 
 92. Describe the Acanthocepltala. 
 
 93. Why are they so called ? 
 
 94. What are the Gordiacece ? 
 
 95. Where do they spend their early life ? 
 
 96. What are they commonly called ? 
 
 97. Why is the class Eclrinodermata so called ? 
 
 98. What animals are included in this class ? 
 
 99. What is meant by "bilateral symmetry" ? 
 
 100. Describe the " test" of a sea-urchin. 
 
 101. How does this test increase in size? 
 
 102. What are the " ambulacral " areas ? 
 
 103. Where are the "genital" and "ocular" plates placed? 
 
 104. Why are they so called? 
 
 105. What is meant by the " madreporiform tubercle" ? 
 
 106. Describe the "tube-feet." 
 
 107. W T hat are " pedicellarke, " and what is their supposed 
 
 function ? 
 
 108. What is the nature and use of the spines ? 
 
 109. How does the covering of the star-fishes differ from that of 
 
 the sea-urchins ? 
 
 110. Describe the digestive organs of the sea-urchins. 
 
94 ZOOLOGY. 
 
 111. Describe the "water- vascular system." 
 
 112. What is meant by " Aristotle's Lantern ?" 
 
 113. What is the course of the circulation in the sea-urchins? 
 
 1 14. What is the nature of the respiration ? 
 
 115. Describe the nervous system. 
 
 116. Give an account of the metamorphosis of the "brittle star.'* 
 
MOLLUSCA CEPHALOPODA. 95 
 
 CHAPTER IV. 
 
 MOLLUSCA AND MOLLUSCOIDA. 
 
 SUB-KINGDOM IV. Mollusca. 
 
 CLASS 1. Cephalopoda. 
 
 128. The Cephalopoda (Gr. Tcepliale, the head; poda, 
 feet) is the highest class of Mollusca. It includes the 
 cuttle-fish, the octopus or poulpe, the calamary or squid, 
 the paper-nautilus, the pearly-nautilus, the extinct am- 
 monites, belemnj.tes, &c. 
 
 This class is characterized by having the organs of 
 locomotion, in the form of arms, arranged in a circle 
 around the mouth. These arms are usually furnished 
 with sucking cups, and are eight or more in number. 
 The body is covered with a loose mantle, which opens in 
 front, on the lower part of the body, to admit water into 
 the gill chamber. The gills are plume-like, and are 
 either two or four in number. They are placed within 
 the mantle. When the water in the gill chamber has 
 been deprived of its oxygen, by the process of respira- 
 tion, it is expelled through a " funnel " placed under the 
 head. The reaction produced by the escape of this water 
 causes the animal to move in the opposite direction. 
 
 The Cephalopoda are all carnivorous animals, and live 
 in the sea. They walk along the sea bottom by means of 
 their long arms ; or swim, partly by the aid of a fin with 
 which the extremity of many of their bodies is furnished, 
 and partly by the reaction caused by the escape of water 
 through the funnel. 
 
 129. Skeleton. The greater number of living cephalo- 
 pods are unprotected by any external shell. Most of 
 these, however, possess an internal shell, but this is 
 sometimes rudimentary. 
 
ZOOLOGY. 
 
 In the cuttle-fishes the internal shell is calcareous, and 
 lies loosely within the mantle. It consists of a broad 
 plate, which terminates behind in an imperfectly cham- 
 bered apex. It is popularly called the " cuttle-bone." 
 The squids or Calamaries (Lat. calamus, a pen) have a 
 horny internal shell, which consists of a central shaft, 
 with two lateral wings. This is termed the " pen." In 
 the SpirulsB the internal shell is whorled, disc-shaped, 
 and chambered, resembling the external shell of the 
 nautilus. The chambers are connected by a tube called 
 the siphuncle (Lat. siphunculus, a little tube). The 
 whorls do not touch one another. 
 
 FIG. 39. A t CDTTLE-FISH (VENTRAL SIDE) ; B, " CUTTLE-BONE." 
 
 The extinct Belemnites (Gr. belemnon, a dart) had an 
 internal shell, consisting of a phragmacoae (Gr. phragma* 
 a division; konos, a cone), a conical chambered shell, 
 which was lodged in a fibrous sheath, called "the guard." 
 This " guard" is the part usually found in the rocks, pre- 
 served as a fossil. 
 
 The only living cephalopods, provided with external 
 shells, are the pearly nautilus (Nautilus PonypiliwJ, and 
 
MOLLUSCA CEPHALOPODA. 
 
 97 
 
 the paper nautilus (Argonauta). The shell of the paper 
 nautilus is spiral, but without chambers. It is secreted 
 by the two webbed arms of the female, but is not attached 
 to the body of the animal. The male is much smaller 
 than the female, and is destitute of a shell. The shell of 
 the pearly nautilus is secreted by the mantle. It is a 
 spiral shell, and is divided into chambers by partitions 
 culled septa (Lat. septum, a partition), which are shaped 
 somewhat like saucers, and are pierced in the centre by a 
 
 V 
 
 Fio. 40. SECTION OP A PEARLY NAUTILUS, showing the chambers traversed by 
 the siphuucle. The animal occupies the last of these chambers. 
 
 membranous siphuncle. As the animal increases in size, 
 it removes to a wider part of the shell, and walls off the 
 part previously occupied by a partition, always occupying 
 the last formed and largest chamber. Each chamber has 
 therefore been occupied by it in succession, and it still 
 keeps up a connection with the vacated chambers by the 
 siphuncle. 
 
 There are many extinct families of cephalopods, allied 
 to the nautilus, whose remains have been deposited in the 
 15 E. G 
 
98 ZOOLOGY. 
 
 rocks from the earliest period. The best known of these 
 is the ammonite, so abundant in the secondary rocks. 
 
 The form of the body is symmetrical, the two sides 
 being alike. The head is distinct, and is surrounded by 
 a circle of arms. These are usually provided with rows 
 of suckers which act like cupping glasses. The poulpe 
 has eight arms which are all alike long. The cuttle-fish 
 has ten arms. Two of them, called tentacles, are much 
 longer than the others, and are only provided with suckers 
 at the extremities. Two of the arms of the paper nautilus 
 are provided with webs which secrete the shell. The 
 pearly nautilus has numerous arms, which are destitute 
 of suckers. The arms are considered to be modified 
 expansions of the part which corresponds to the foot in 
 other molluscs. 
 
 130. Digestion. The mouth leads into a cavity which 
 contains two horny jaws and a tongue. The jaws work 
 vertically, and bear some resemblance to the beak of a 
 parrot. The tongue is partly covered with recurved 
 siliceous spines. It has been called by Professor Huxley 
 an odontophore, or " tooth bearer." " It consists essen- 
 tially of a cartilaginous cushion, supporting as on a pulley, 
 an elastic strap, which bears a long series of transversely 
 disposed teeth. The ends of the strap are connected with 
 muscles attached to the upper and lower surface of the 
 hinder extremities of the cartilaginous cushions ; and these 
 muscles, by their alternate contractions, cause the toothed 
 strap to work backwards and forwards, over the end of 
 the pulley formed by its anterior end. The strap conse- 
 quently acts, after the fashion of a chain-saw, upon any 
 substance to which it is applied, and the resulting wear 
 and tear of its anterior teeth are made good by the 
 incessant development of new teeth in the secreting sac 
 in which the hinder end of the strap is lodged. Besides 
 the chain-saw-like motion of the strap, the odontophore may 
 be capable of a licking or scraping action as a whole." 
 (Huxley.) The cavity of the mouth is succeeded by a 
 gullet which leads to a stomach and intestine, The 
 
MOLLUSCA CEPHALOPODA. 
 
 09 
 
 gullet is provided with salivary glands. The intestine 
 opens on the ventral surface near the base of the funnel. 
 This funnel is a muscular tube, situated under the 
 head. It communicates at one extremity with the cavity 
 of the mantle, and at the other with the external medium. 
 The naked cephalopods are provided with a gland called 
 the ink bag, which opens into the gill chamber near the 
 anus. It discharges its contents through the funnel, 
 and darkens the water, thus covering their retreat when 
 pursued by an enemy. 
 
 131. Circulation. The blood is colourless. The heart 
 contains two cavities, an auricle and a ventricle. The 
 
 Fio. 41. A, OCTOPUS OR POULPE; J5, THE MANTLE OF THE POULPE REMOVED 
 
 FROM THE RIGHT SIDE. 
 
 &, the right gill ; o, the free margin of the branchial sac ; t, the funnel. 
 
 aerated blood from the gills passes into the auricle, thence 
 to the ventricle which drives it through the body. In 
 the cuttle-fishes, at the base of each gill, there is a special 
 cavity which by its contraction drives the venous blood 
 
100 ZOOLOGY. 
 
 that lias come from the various parts of the body through 
 these organs. These cavities are called branchial hearts. 
 They are wanting in the nautili. In the cuttle-fishes, &c., 
 the veins and arteries are connected by capillaries. It is 
 worthy of note, that while the blood in the heart of a 
 fish is venous, the heart of a mollusc contains arterial 
 blood. 
 
 132. Respiration. All cephalopods breathe by gills or 
 branchiae. These are plume-like organs, placed on the 
 sides of the animal in a cavity formed by the mantle 
 which opens in front on the under surface of the body. 
 When the mantle expands, water is forced into this 
 cavity ; when it contracts, it is ejected through the 
 funnel, which is provided with a valve, allowing water to 
 pass towards the head, but not otherwise. The reaction 
 produced by the escape of this water causes the animal 
 to move in the opposite direction, that is, tail foremost. 
 Thus, in the cephalopods, as in many other animals, 
 the functions of locomotion and respiration are intimately 
 associated. 
 
 The cuttle-fish tribe and the paper nautilus are 
 each provided with two gills ; the pearly nautilus with 
 four. 
 
 133. The nervous system consists, as in the other Mol- 
 lusca, of three ganglia united by nervous cords the cere- 
 bral, pedal, and parieto-splanchnic ganglia. The cerebral 
 ganglia are large, and are surrounded by a cartilaginous 
 ring which may be considered a rudimentary skull. 
 This is the nearest approach to an internal skeleton 
 found in any invertebrate animal. There are two large 
 eyes situated on the sides of the head. 
 
 134. Development. The Cephalopoda are unisexual 
 animals. Their ova are of large size comparatively. In 
 the cuttle-fishes one of the arms of the male is adapted for 
 conveying to the gill chamber of the female the sperm-cells 
 which have previously been formed into a mass by a 
 glutinous substance. In the common octopus or poulpe, 
 the third arm on the right side has at first the appearance 
 
MOLXUSDA-r-f TEROPC/ECAi 
 
 101 
 
 of a small bladder. When this bladder bursts, the arm is 
 liberated. It is now considerably longer than the 
 others, and is provided with an oval plate at the 
 extremity, which is believed to be used, like the modi- 
 fied palpi of the male spiders, in conveying sperm to 
 the female. 
 
 In the paper nautilus, this modified arm is detached 
 from the body of the male, and lodged in the mantle 
 chamber of the female, a fresh arm being from time to 
 time developed. When first discovered in this position, 
 it was believed to be an internal parasite, and received 
 the name of lieztocotylus (Gr. hekaton, a hundred ; kotulos, 
 a cup), because of its numerous sucking cups. 
 
 CLASS 2. Pteropoda. 
 
 135. The Pteropoda (Gr. pteron, a wing ; poda, feet) 
 are so called because their organs of locomotion consist of 
 two fin-like expansions of the foot (epipodia) placed 
 011 each side of the head. 
 
 They are very small animals. 
 They swim near the surface, 
 sometimes in vast numbers, in 
 the deeper parts of the ocean. 
 The Clio Rorealis, a naked species, 
 not more than an inch in length, 
 forms the principal food of the 
 Baleen whale. 
 
 Professor Huxley places the 
 Dentalium, which is common 
 enough on our own coasts, among 
 the Pteropoda. 
 
 136. Skeleton. -The body is 
 covered with a mantle, which 
 generally secretes a univalve 
 shell of a glassy substance. This 
 
 shell sometimes consists of two pieces united at the 
 
 FIG. 42. HY ALE A. 
 
102 :>;OG,LOGY. 
 
 edges, and is often of a spiral form, not unlike a small 
 nautilus. Some species are destitute of a shell. 
 
 137. Digestion. There usually is no distinct line of 
 separation between the head and the body. The mouth 
 is surrounded by tentacles, and has an odontophore. 
 There is a stomach, liver, and intestine, with anal open- 
 ing, on the ventral surface of the body. They are said to 
 subsist on small Crustacea, &c. 
 
 138. Circulation. There is a heart with two cavities, 
 an auricle, and a ventricle. 
 
 139. Respiration is effected by a portion of the sur- 
 face which is covered with cilia. This is sometimes 
 placed in a chamber within the mantle, and is sometimes 
 external. 
 
 140. The Nervous System consists of three pairs of 
 ganglia. The principal mass is below the oesophagus. 
 
 141. Development. All the Pteropoda are hermaphro- 
 dite, male and female organs being united in each indi- 
 vidual. The young undergo metamorphosis. 
 
 CLASS 3. Gasteropoda. 
 
 142. The Gasteropoda (dr.gaster, the belly; 
 is a very large class. It includes land-snails, sea-snails, 
 fresh-water snails, slugs, limpets, whelks, &c. It is so 
 called, because the organ of locomotion generally consists 
 of a flat muscular disc occupying the lower part of the 
 body, which is termed the " foot." By the alternate con- 
 traction and expansion of this organ they glide slowly 
 along. In the Heteropoda (Gr. heteros, diverse; poda, feet), 
 the foot is furnished with fin-like expansions, which adapt 
 the animal for swimming. The hinder part of the foot, 
 in many of the Gasteropoda, is provided with a horny or 
 calcareous plate, called the operculum (Lat. operculum, a 
 lid). When the animal retreats within the shell, which 
 it is enabled to do by the retractor muscle, this operculum 
 closes up the aperture. 
 
MOLLUSCA GASTEROPODA. 
 
 ica 
 
 143. Skeleton. The Gasteropoda are provided with a 
 mantle which encloses the body like a sac. This mantle, 
 in most cases, secretes a shell, which is generally univalve, 
 or composed of a single piece. A few have multivalve 
 shells, which are composed of eight pieces, placed one 
 behind another. None possess a bivalve shell. Some. 
 
 .0. 
 
 t... 
 
 FIG. 43. ANATOMY OF THE SXAIL. 
 
 to, ocular tentacles; oe, oesophagus; sn, cerebral ganglion; j, gizzard ; 
 e, stomach; t, liver;/, biliary ducts; i, intestine; a, anus; r, kidney; p, 
 breathing organ ; c, heart. 
 
 as the common slugs, are destitute of shells. The univalve 
 shell is either a simple cone, as in the limpet; or "spiral," 
 which is its most usual form The various coils of the 
 
104 ZOOLOGY. 
 
 spiral are called whorls. The last whorl is the largest, 
 and is termed the body whorl. The part of the shell 
 above the body whorl is the spire. The sutures are the 
 lines of junction of the whorls. Sometimes the whorls do 
 not form a, spire, but are in the same plane, forming a 
 disc, as in the fresh water shell Planorbis. In the vegetable- 
 feeding gasteropods, the aperture or mouth of the shell is 
 unbroken or " entire." These are therefore called holo- 
 stomata (Gr. holos, whole; stoma, mouth). In the carni- 
 vorous species, the mouth of the shell is notched or drawn 
 out into a canal for the protection of a breathing siphon. 
 Sometimes there are two of these canals or notches. 
 These breathing tubes have no immediate connection with 
 the carnivorous habits of the animals. 
 
 144:. Digestion. The head is very distinct, and is 
 usually furnished with two long tentacles. There are also 
 often two stalks, on the summit of which the eyes are 
 placed. The mouth is sometimes furnished with two 
 homy jaws. There is always an odontophore, armed with 
 siliceous teeth, similar to that possessed by the Pteropoda 
 and Cephalopoda. The mouth leads to a gullet, which is 
 succeeded by a stomach and convoluted intestine. In 
 vegetable feeders, the stomach is often provided with 
 calcareous plates, which assist in grinding the food. The 
 anus is placed on the right side, in the front part of the 
 body. There are salivary glands and a liver. 
 
 145. Circulation. There is usually a distinct heart, 
 with two cavities an auricle and a ventricle. 
 
 146. Respiration is variously effected in the different 
 groups. The land snails and slugs, and some fresh water 
 gasteropods (Limncea, &c.), breath air directly by means 
 of a pulmonary chamber hollowed out on the right side 
 of the body near the head. This chamber is provided 
 with an opening to admit the air, and its walls are lined 
 with a membrane containing numerous blood-vessels. 
 This group of air-breathers is placed by Professor Huxley 
 in a separate class the Pulmo-Gasteropoda. 
 
 Those that breathe air through the medium of water 
 
MOLLUSCA GASTEROPODA. 
 
 105 
 
 (Brancliw-G aster opoda) perform the respiratory function 
 in three different ways 
 
 1. Some of the Ileteropoda have no special breathing 
 organs. The walls of the mantle-cavity are supplied 
 with blood-vessels, and the blood in passing through 
 these is purified by the air contained in the water. 
 
 2. The sea-slugs, &c. have external breathing organs, 
 consisting of tuft-like expansions of the integument 
 placed on the back and sides of the animal. These are 
 called Nudibranchiata, (Lat. nudus, naked ; Gr. branchia, 
 gills), and may be found on sea-weeds or under stones on 
 the sea-shore. 
 
 FIG. 44. CARIXARIA AND ITS SHELL (Ileteropoda.) 
 
 3. In the majority of cases, the gills are plume-like 
 organs, contained in a chamber, formed by a fold of the 
 mantle. In many members of this group, the water is 
 conveyed to the gill chamber through a siphon, formed 
 by a prolongation of the mantle fold. This water passes 
 off through an aperture which is often furnished with 
 another siphon. 
 
 147. The Nervous System consists of three pairs of 
 ganglia the cerebral, pedal, and parieto-splanchnic. 
 These are united by nervous threads. There are two 
 eyes, often placed at the summit of a pair of stalks. In 
 the land snails, these stalks are tubular, and contain 
 muscular threads, which, by their contractions, pull the 
 eyes into the interior of the tubes, when the animal is 
 apprehensive of danger to these important organs. There 
 are two auditory vesicles, filled with fluid, and contain- 
 ing otoliths (Gr. ous, an ear ; lithos, a stone), which are 
 in a constant state of vibration. These organs are placed 
 at the bases of the tentacles. 
 
108 ZOOLOGY. 
 
 148. Development. The sexes are usually distinct, 
 but are united in the sea-slugs. The young, when hatched, 
 have a shell in all cases. The naked molluscs soon cast 
 this off. The young of the water-breathing species are 
 furnished with a pair of ciliated fin-like expansions, 
 resembling the wings of the Pteropoda, by which they 
 are enabled to swim with great facility. This is one of 
 many instances, in which the larval form of one group 
 resembles the permanent form of another. 
 
 CLASS 4. Lamellibranchiata. 
 
 149. The Lamellibranchiata (Lat. lamella, a plate; 
 Gr. branchia, gill) are so called, because they are pro- 
 vided with two gills or branchise on each side of the body, 
 in the form of membranous plates or leaves. They are 
 also called Conchifera (Lat. concha, a shell ; fero, I bear), 
 and sometimes Acephala (Gr. a, without; cephale, the 
 head). They are always provided with bivalve shells. 
 These may be distinguished from the bivalves of the 
 Brachiopoda, by being usually equivalve and inequi- 
 lateral; whereas, the brachiopod bivalves are always 
 equilateral, and never equivalve. They have a mouth, 
 but no distinct head. The lingual ribbon, or odonto- 
 phore, found in the higher molluscs, is absent. 
 
 The Lamellibranchiata is a very numerous class, in- 
 cluding all the bivalve shell-fish ordinarily met with. 
 They are all aquatic. Most of them inhabit the sea, but 
 a few live in fresh water. Mussels, cockles, oysters, and 
 scallops are familiar examples. 
 
 150. Skeleton. The mantle, instead of surrounding 
 the animal like a sack, as in the Gasteropoda, is divided 
 into two halves, or lobes, which are placed on the right 
 and left sides of the body. Sometimes the mantle lobes 
 are unconnected ; at other times they are united, except 
 at two points, where there are openings for the passage of 
 the foot and the breathing siphons. Each lobe secretes a 
 
MOLLUSCA LAMELLIfcRANCHIATA. 107 
 
 separate shell, formed of carbonate of lime. These shells 
 are really cones with their apices turned to one side - 
 that in which the mouth of the animal is situated. The 
 apex, where the growth of the shell commences, is termed 
 the umbo, or beak. The beaks are situated at the dorsal 
 part of the shell. The opposite part, where the shell 
 opens, is the base. The side of the shell, towards which 
 the beaks point, is called the anterior side, because the 
 mouth of the animal is placed near it. The opposite is 
 the posterior side. The length of the shell is measured 
 from tKe anterior to the posterior side ; the breadth from 
 the beaks to the base. The anterior side is usually 
 shorter than the posterior ; the shell is therefore said to 
 be inequilateral. The valves are generally equal in size; 
 that is, they are equivalve. The shells of the scallop and 
 oyster, however, are inequivalve. As the mouth is 
 situated near the anterior margin, the valves are conse- 
 quently placed on the sides of the animal, and are there- 
 fore termed right and left. In the Brachiopoda, as 
 already noticed, the valves are placed on the dorsal and 
 ventral surfaces of the body, and are always equilateral 
 and inequivalve. 
 
 Near the beaks is a line called the hinge line, where 
 the valves are united together by a series of projections 
 called teeth, which fit into corresponding cavities in the 
 opposite valves. The valves are bound together by a 
 structure termed the ligament, of which there are usually 
 two parts one external, the other internal. This liga- 
 ment is placed immediately behind the beaks. The ex- 
 ternal ligament is a fibrous horny substance, which is 
 always stretched when the valves are shut. The internal 
 ligament, or cartilage, consists of elastic fibres, which 
 are placed perpendicularly between the two valves. 
 When the valves are shut, these fibres are compressed 
 and shortened. When the pressure is removed, the liga- 
 ments open the valves by their elasticity. 
 
 The valves are shut by the adductor (Lat. ad. to ; 
 duco, I lead) muscles. There are sometimes two of these 
 
108 
 
 ZOOLOGY. 
 
 muscles, and sometimes only one. One is placed in the 
 anterior part of the shell, and one in the posterior. The 
 anterior muscle is sometimes absent. These muscles 
 leave impressions in the interior of the valves, so that it 
 can be easily ascertained, by examining a shell, whether 
 the living animal had one or two. The valves in ordi- 
 nary circumstances are kept open; but, when the animal 
 is alarmed, it exerts its adductor muscles, and closes 
 them. A dead bivalve always gapes, because, when the 
 adductor muscles cease to act, the elasticity of the liga- 
 ment opens the valves. 
 
 FIG. 45. VENUS, showing Foot and Breathing Siphons. 
 
 Most lamellibranchs possess a foot, which is pro- 
 truded through an opening in the mantle, on the lower 
 surface of the body. The foot is a muscular organ, 
 sometimes finger-shaped, and sometimes bent like a sickle. 
 This foot enables the animals, in some instances, to move 
 along by making a number of short leaps. In other 
 cases it is used in making burrows in the sand or mud. 
 In the mussels, &c., the foot is furnished with a gland 
 which secretes a silky substance. Of this liquid silk, 
 the creature forms a tuft of thread, by which it attaches 
 itself to a stone or some other object. The foot is some- 
 
MOLLUSCA LAMELLIBRANCHIATA. 109 
 
 times very small. In the oyster tribe it is altogether 
 absent. 
 
 The animal is provided with muscles, by which it is 
 enabled to protrude or retract the foot at will. These 
 retractor muscles of the foot leave certain markings in 
 the interior of the shell, which are called the pedal 
 impressions. 
 
 There are other " impressions " in the interior of the 
 shell, of which the principal are the pallial line, and 
 the pallial sinus. 
 
 The pallial (Lat. pallium, a cloak) line marks the 
 impression made by the margin of the mantle. 
 
 The pallial sinus (Lat. sinus, a bay), is an indentation 
 in the pallial line, found in those species that have re- 
 tractile breathing siphons. The depth of the indentation 
 corresponds with the length of the siphons. 
 
 151. Digestion. The Lamellibranchiata are destitute 
 of a distinct head. The mouth is placed in the front 
 part of the body, and is furnished with one or two pairs 
 of membranous organs called palpi. There are no teeth. 
 The mouth is followed by a gullet which conducts to a 
 stomach and convoluted intestine. The intestine passes 
 through the heart, and terminates in an anus, placed 
 near the aperture of the breathing siphon. There is a 
 large liver, but no salivary glands. Their food consists 
 principally of small animalcules. 
 
 152. Circulation. There is a well developed heart, 
 consisting often of three chambers two auricles and one 
 ventricle. Sometimes there is only one auricle and one 
 ventricle, as in the oyster. In a few instances there are 
 two hearts, placed in different parts of the body, each 
 composed of an auricle and a ventricle. There are arteries 
 which convey the blood from the ventricle through tho 
 body, and veins which carry it to the gills, where it is 
 rerated. From these it is brought back to the auricle or 
 auricles. 
 
 153. Respiration. The organs of respiration consist 
 of a pair of plate-like gills on each side of the body. 
 
110 ZOOLOGY. 
 
 These gills are attached along their dorsal margins. 
 Sometimes there is only one gill 011 each side. When 
 viewed by a microscope, these gills are seen to consist 
 of a number of minute "tubular rods supporting a 
 network of blood-vessels. " They are covered with 
 cilia, which, by their perpetual movements, keep up 
 a constant current of water. This current not only 
 supplies fresh water for the purification of the blood, 
 
 FIG. 46. ANATOMY OF THE OYSTER. 
 
 s, mouth ; e, stomach ; i i, intestinal canal ; a, anus ; b g, nervous gang-lia; 
 m t, mantle ; & (figure to the left), branchiae ; m, adductor muscle ; o, ovary. 
 
 but also brings minute particles of food for the sustenance 
 of the animal. 
 
 Those lamellibranchs that live buried in sand or mud 
 are provided with two respiratory siphons or tubes. One 
 of these admits a current of water which passes over the 
 gill plates, supplies the mouth with such food as the 
 water may contain, and is then discharged through the 
 other siphon, carrying with it the excretions from the 
 intestine. These siphons are sometim.es longer than the 
 shell, and in other cases are very short. When the ani- 
 mal buries itself, it always leaves the extremities of the 
 
MOLLUSCOIDA BRACHIOPODA. Ill 
 
 siphons exposed at the surface. The siphons are some- 
 times separated from one another; in other instances they 
 are united along one side, forming a compound tube. The 
 animal has generally the power of withdrawing the si- 
 phons within the shell. The muscle by which this is 
 effected is termed the retractor muscle of the siphons. 
 The indentation produced in the pallial line by the action 
 of this muscle has already been described. 
 
 154. The Nervous System consists of the three normal 
 pairs of ganglia the cerebral pair, placed near the 
 mouth ; the pedal pair in the foot ; the parieto-splanchnic 
 pair, which supplies filaments to the mantle, gills, and 
 other internal organs. These ganglia are connected by 
 nervous cords. 
 
 Eyes are present in the form of minute coloured spots 
 which are " set at intervals like a row of sentinels," 
 round the borders of the mantle. 
 
 Auditory sacs, containing otoliths, are placed near the 
 pedal ganglia. 
 
 155. Development. The sexes are generally separate, 
 but are united, in some cases, in the same individual. 
 The ova are retained within the body of the parent until 
 they are hatched. When set free, they are able to swim, 
 being furnished with cilia. Thus, the fry or spat of the 
 oyster can move about, while the adult animal is sessile. 
 
 SUB-KINGDOM V. Molluscoida. 
 CLASS 1. Brachiopoda. 
 
 156. The Brachiopoda (Gr. brackia, arms ; poda, feet) 
 are so called, because they are provided with two long 
 arms which are coiled up within the shell. They are all 
 marine animals ; and, as most of them inhabit the deep 
 seas, they are less known than the shells of the true 
 molluscs are. They are often called lamp-shells, as 
 piany of them have a striking resemblance to an ancient 
 
112 ZOOLOGY. 
 
 lamp. They have a very wide range, being found in all 
 latitudes, and at various depths of sea bottom. They are 
 much more commonly met with as fossils than as recent 
 shells, nearly two thousand extinct species having been 
 described, while less than one hundred living species are 
 known. They are found in all the geological formations 
 from the Cambrian upwards. They are especially abun- 
 dant in the Silurian rocks. 
 
 FIG. 47. ANATOMY OF TEREBKATULA (the animal withdrawn within its shell). 
 
 a a, mantle ; c c, peduncle ; d d' d", muscles which open and close the valves; 
 e, stomach ; i i, intestine ; lc y pseudo-heart; n n, ciliated arms; o, oviduct. 
 
 157. Skeleton. The Brachiopoda, like the Lamelli- 
 branchiata, possess bivalve shells. The valves of the 
 brachiopod shells are always more or less unequal in size. 
 The shells are therefore said to be inequivalve. They 
 are equilateral that is, the two sides of the valves are 
 equal and symmetrical. On the other hand, the valves of 
 the Lamellibranchiata are generally equal in size, but are 
 always inequilateral and unsymmetrical. The valves are 
 dorsal and ventral, instead of being right and left, as in 
 the Lamellibranchiata. The ventral valve is always the 
 larger. 
 
 The valves are often united together, along a hinge 
 
MOLLUSCOIDA BRACHIOPODA. 
 
 113 
 
 lino, by two teeth attached to the ventral valve, which 
 are inserted in sockets in the dorsal valve. There is no 
 ligament, the valves being both opened and closed by the 
 action of special sets of muscles. The shells are generally 
 calcareous, but in the Lingula they are of a horny 
 texture. 
 
 The ventral valve is usually provided with a long beak 
 which is often perforated to allow the passage of a mus- 
 cular stalk, called the peduncle (Lat. pedunculus, a stalk), 
 by which the animals are attached to rocks, corals, &c. 
 The Terebratula (Lat. a little bore hole) derives its 
 name from this aperture. This peduncle sometimes 
 passes out between the valves, and in other cases the 
 animal is attached by the beak of the ventral valve, the 
 peduncle being- absent. It is believed that some fossil 
 
 FIG. 48. FOSSIL BRACHIOPODA. 
 Rhynchonella Productus Spirifer. 
 
 groups were alUe to move about freely. The valves are 
 lined by the mantle lobes. The interior of the shell 
 usually contains a calcareous skeleton, attached to 
 the inner surface of the dorsal valve, upon which the 
 arms are supported. In the extinct spirifers, this skeleton 
 was coiled up like a pair of watch springs. In the Tere- 
 bratula it has the form of a loop. 
 15 E. H 
 
114 ZOOLOGY. 
 
 158. Digestion. The digestive organs are confined to 
 a very small space near the beak of the shell. This space 
 is separated from the rest of the interior cavity by a 
 membrane, in the centre of which the mouth is placed. 
 The mouth is furnished with two arms, which correspond 
 to the labial tentacles of the Lamellibranchiata. It was 
 formerly thought that the animal had the power of pro- 
 truding these arms, but it is now believed that they 
 remain permanently coiled up within the shell. They 
 are often three or four times the length of the shell, and 
 occupy a large portion of the interior cavity. They are 
 furnished on one side with a fringe of filaments, called 
 cirri (Lat. cirrus, a curl). These cirri are provided with 
 microscopic cilia, which produce a current in the water, 
 and thus bring a supply of food. 
 
 The mouth leads to a gullet and stomach, which is 
 surrounded by a large liver. The intestine in some cases 
 terminates in a blind sac ; in others it is provided with 
 an anal opening. It is always completely shut off from 
 the cavity of the body. 
 
 159. Circulation. The heart is in the form of a simple 
 sac, without any valve or partition, and is placed on the 
 dorsal side of the stomach. The course of the circulation 
 has not been fully ascertained. 
 
 These animals possess what Professor Huxley has 
 termed an atrial (Lat. atrium, a hall) system, from its 
 resemblance to the atrial chamber in the Ascidians. It 
 consists of a series of canals which communicate with the 
 exterior by two or four organs, called false hearts, because 
 they were formerly believed to be connected with the 
 blood vascular circulation. The object of the system 
 seems to be to carry off excretions, and the products of 
 the generative organs. 
 
 160. Respiration was formerly thought to be effected 
 solely by the mantle ; hence the name PalliobrancMata 
 (Lat. pallium, a cloak ; Gr. branchia, a gill) was given to 
 this class. The long fringed arms are now believed to 
 discharge the office of purifying the blood, 
 
MOLLUSCOIDA TUNICATA. 115 
 
 161. The nervous system consists of a single principal 
 ganglion, which, in those groups that have the valves 
 united by a hinge, is connected with a chain of ganglia 
 passing round the gullet. 
 
 162. Development. The sexes are sometimes distinct; 
 in other cases they appear to be united in the same in- 
 dividual. The young are believed to be able to swim 
 about by the action of their fringed arms. 
 
 163. Divisions. They are divided into two groups 
 the Articulata and Inarticulate, In the Articulata the 
 valves are united along the hinge line by teeth and 
 sockets. The intestine ends in a blind sac. The mantle 
 lobes are united dorsally. The Terebratula belongs to this 
 division. In the Inarticulata the valves are not united 
 by teeth. The intestine is provided with an anal opening. 
 The mantle lobes are not connected. The Lingula is an 
 example of this group. 
 
 CLASS 2.Tunicata, or Ascidioida. 
 
 164. The Tunicata (Lat. tunica, a cloak) are so called 
 because they are covered with a leathery integument. 
 They are also called Ascidioida (Gr. askos, a wine bag), 
 because many of them are shaped like a double-necked 
 bottle. When touched, they discharge a jet of water; on 
 this account they have received the popular name of sea- 
 squirts. They are all marine animals, and may generally 
 be found on our coasts attached to sea-weeds, or shells, 
 especially after a storm. They are easily known by their 
 two prominent apertures. 
 
 Some of the Ascidians are single, or simple. These 
 are fixed to some solid object, such as a submerged stone. 
 The social Ascidians form a colony by budding. They 
 are connected by a tube, through which the blood common 
 to the colony flows. In the compound Ascidians the 
 tests are joined together into a mass, but there is no 
 common circulation. Other groups float about on the 
 
116 ZOOLOGY. 
 
 surface of the sea. Some of these, as the Pyrosoma (Gr. 
 
 pur, fire; soma, a mouth), are phosphorescent, and light 
 
 up the sea in tropical regions 
 with a pale greenish light. 
 
 165. Skeleton, or Cover- 
 ing. In the simple Asci- 
 dians the covering consists 
 of two coats, an outer and 
 an inner. The outer coat is 
 
 rough and leathery in tex- 
 49.-SOCIAL ASCIDIAXS. tur ^ j t is ca]led tlie tegt 
 
 or external tunic. It is largely composed of cellulose, a 
 chemical substance closely allied to the woody fibre of 
 plants. This substance is rarely found in animal tissues. 
 The inner integument, or mantle, is muscular. It is 
 by means of its contractability that the animal is able 
 to squirt out water through one of its apertures. 
 
 166. Digestion. The two orifices are usually guarded 
 by short tentacles, which are not furnished with cilia. 
 The upper or oral opening leads into a chamber which 
 occupies a large portion of the interior of the animal. 
 This is usually called the respiratory or branchial sac. 
 Its walls are perforated like a sieve, the apertures being 
 lined with cilia. At the lower extremity of this sac the 
 entrance to the gullet is situated. The gullet leads to a 
 stomach and intestine, which is bent round, so as to reach 
 a cavity connected with the other aperture, called the 
 cloaca or atrial (Lat. atrium, a hall) chamber. A cur- 
 rent of water constantly passes in at the oral aperturo 
 into the respiratory chamber, and through its perforated 
 walls to the atrial chamber. This current is produced by 
 the movements of the cilia which line the apertures of 
 the respiratory sac, the cilia working so as to produce a 
 current in that direction. From the atrial chamber the 
 water is discharged through the atrial aperture to the 
 surrounding medium, having in its passage not only 
 brought food to the stomach, but also carried off the ex- 
 cretions supplied by the intestine. 
 
MOLLUSCOIDA POLYZOA. 117 
 
 167. Circulation. The heart is iii the form of a simple 
 muscular tube, open at both ends, and without valves. 
 By the peristaltic motions of this tube circulation is 
 effected. For a definite number of times the blood is 
 propelled in one direction ; then, the action of the tube 
 being reversed, it flows as many times in the opposite 
 direction. Thus the two ends of this tubular heart per- 
 form alternately the functions of an artery and a vein. 
 
 168. Respiration. The walls of the respiratory cham- 
 ber are richly supplied with blood-vessels. The blood in 
 these vessels is aerated by the air contained in the water 
 which constantly flows through it. This current of water 
 not only brings food to the animal, but also brings oxygen 
 for the purification of its blood. Thus, in the ascidians, 
 as well as in the Mollusca proper, the functions of respira- 
 tion and alimentation are intimately associated. 
 
 169. The nervous system consists of a single ganglion 
 placed between the oral and atrial apertures. There are 
 generally eye-like spots between the tentacles that sur- 
 round the mouth. There is also an auditory vesicle con- 
 taining an otolith. 
 
 170. Development. The ascidians are all hermaphro- 
 dite, the sexes being united in the same individual. The 
 young in some groups resemble tadpoles, being free- 
 swimming, and provided with long tails. 
 
 CLASS 3. Polyzoa. 
 
 171. The Polyzoa (Gr. polus, many ; zoon, an animal) 
 is the lowest class of the Molluscoida. It includes 
 the " sea-mosses " and the Flustra or sea-mats. These 
 animals were formerly placed along with the Hydrozoa, 
 which they very much resemble in outward appearance ; 
 their internal structure, however, is widely different. 
 From their resemblance to plants, they are often called 
 Zoophytes (Gr. zoon, an animal ; phuton, a plant). Most 
 of them inhabit the sea, but some species live in fresh 
 water. They are compound animals, forming colonies 
 
118 
 
 ZOOLOGY. 
 
 which have been produced by gemmation (Lat. gemma, a 
 bud), or budding from a single individual. These colonies 
 are provided with a chitinous or calcareous integument. 
 
 FIG. 50. FLUSTRA. 
 
 The Flustra may be readily found covering the large 
 fronds of the Laminarian sea- weed with a lace-like crust. 
 Other species are spread over shells or submerged stones. 
 Others look like diminutive shrubs, and are merely attached 
 
MOLLUSCOIDA FOLYZOA. 119 
 
 by one extremity to some solid object. They are so very 
 minute that 1,800 cells, each containing a separate animal, 
 Lave been found in one square inch of surface. 
 
 To the outside of some of the cells certain organs are 
 often attached which bear a considerable resemblance to 
 the beak of a bird. They have been called avicularia 
 (Lat. avicula, a little bird), or " bird's head processes." 
 The beak consists of two mandibles, the lower of which 
 only is movable. This organ is quite independent of the 
 animal to which it is attached, for it continues its snapping 
 movements long after the death of the zooid. The use 
 of these curious appendages is not known. They are 
 supposed to bear some analogy to the pedicellarise of the 
 sea-urchins and star-fishes. 
 
 A colony f these animals is called a polyzoarium, 
 each individual animal a polypide. The term zooid is 
 used both in Hydrozoa and Polyzoa, as a common designa- 
 tion for the individual organisms that make up a colony 
 which has been produced by gemmation or budding. 
 
 172. Skeleton. Each polypide is enclosed in a double- 
 walled cell. The outer layer is either chitinous or cal- 
 careous, and is called the ectocyst (Gr. ektos, without ; 
 hustis, a bladder). The inner lining of the ectocyst is 
 membranous, and is called the endocyst (Gr. endon, 
 within; kustis, a bladder). There are two openings in this 
 membrane, one for the mouth and the other for the anus. 
 These openings are generally placed near one another. 
 
 173. Digestion. The mouth is surrounded by a num- 
 ber of hollow tentacles which are provided with cilia. In 
 the marine species, these tentacles are arranged in the 
 form of a circle ; in those that live in fresh water, they 
 assume the shape of a crescent or horse-shoe. The cilia, 
 by their perpetual movements, produce little whirlpools in 
 the water which supply the animals with those nutritious 
 particles on which they subsist. 
 
 When the animal is alarmed, it is able by a special set 
 of muscles, connecting the lower wall of the cell with the 
 gullet, to retract the front part of the alimentary tube 
 
120 
 
 ZOOLOGY. 
 
 with, its attached crown of tentacles, as well as the anterior 
 part of the membranous sac, within the posterior part 
 of this sac, by a process of inversion, 
 somewhat similar to that by which a 
 snail withdraws its eye-stalks. 
 
 The mouth leads to a gullet and stomach, 
 a muscular gizzard sometimes intervening. 
 The intestine is bent upon itself, so that the 
 anal opening is placed near the mouth. The 
 whole peri visceral cavity is filled with fluid. 
 174. Circulation. No heart has yet 
 been discovered in any Polyzoon. The 
 products of digestion pass through the 
 walls of the intestine, and become mixed 
 with the surrounding fluid. 
 a, branchial iyg Respiration appears to be effected 
 
 plume; w, ccsopha- r 
 
 gus; c, stomach; by the ciliated tentacles, probably assisted 
 fnusf/fe^sui by the fluid which fills the peiivisceral 
 pended Win the cavity. This fluid is slowly replaced by 
 the action of the cilia which line the in- 
 terior walls of the endocyst. 
 
 176. Nervous System. Between the mouth and the 
 anal aperture there is placed a single ganglion, which 
 sends off nerves in different directions. There is also 
 said to be a " colonial nervous system," forming a means 
 of communication between the various polypides in a 
 colony. It is believed to be by means of this nervous 
 system that the avicularia are able to continue their 
 motions after the death of the zooids, 
 
 177. Development. In the Polyzoa the sexes are united 
 in the same individual. The reproductive organs are 
 attached to the inner surface of the endocyst. The ova 
 pass into the perivisceral cavity, where they are fertilized. 
 How they make their escape from the cell has not been 
 ascertained. The embryo is at first able to swim about 
 by the action of its cilia. After a time it attaches itself 
 to some fixed object, and originates a new colony, the 
 number of zooids being increased by continuous budding. 
 
 FIG. 51. PLUM A' 
 
 TELLA. 
 
QUESTIONS. 121 
 
 QUESTIONS IV. 
 
 1. What is the derivation of the terra Cephalopoda ? 
 
 2. Give examples of this class. 
 
 3. What are its distinctive characters ? 
 
 4. What is the habitat of these animals ? 
 
 5. What are their habits ? 
 
 6. Describe the "arms," the "funnel," and the "mantle." 
 
 7. What are the distinctive features of the arms in the Poulpe, 
 
 the Cuttle-fish, the Paper Nautilus, and the Pearly 
 Nautilus ? 
 
 8. How is locomotion effected ? 
 
 9. What cephalopods possess an external shell ? 
 
 10. Describe the external shell, and show how it differs from 
 
 the univalve shell of the Gasteropoda. 
 
 11. What members of this class have an internal shell? 
 
 12. What cephalopods are destitute of a shell? 
 
 13. What is the nature of " cuttle-bone " ? 
 
 14. Describe the "pen" of the calamary. 
 
 15. Describe the internal shell of the Spirulce. 
 
 16. What are Belemnites ? 
 
 17. What are Ammonites ? 
 
 18. W^hat is the nature of the digestive apparatus in this class ? 
 
 19. Describe the "jaws" and the odontophore. 
 
 20. Describe the "ink-bag," and state whether it is possessed 
 
 by all the members of this class. 
 
 21. Describe the heart and circulatory organs. 
 
 22. What are ' ' branchial hearts " ? 
 
 23. What cephalopods are destitute of these organs ? 
 
 24. Does the heart contain venous or arterial blood 1 
 
 25. Describe the breathing organs. 
 
 26. How is respiration effected? 
 
 27. Show that respiration and locomotion are associated in this 
 
 class. 
 
 28. On what principle are the Cephalopoda divided into orders ? 
 
 Name the orders. 
 
 29. Give an account of the nervous system and the organs of 
 
 sight. 
 
 30. What is a Hectocotylus ? 
 
 31. Why are the Pteropoda so called? 
 
 32. Give examples of this class. What is their usual habitat ? 
 
 33. Describe the shell of the Pteropoda. 
 
 34. What is the nature of their digestive apparatus ? 
 
 35. How is respiration effected ? 
 
 36. Explain the term Gasteropoda. 
 
122 ZOOLOGY. 
 
 37. ("Hive examples of tins class, and state whether they live on 
 
 land, in fresh water, or in the sea. 
 *'S. I low is locomotion effected in this class ? 
 :;'.>. What is meant l>y tin; "foot"? 
 
 40. What arc the //</< roj>oif<i, '! 
 
 41. What is the operculum ? 
 
 42. Descriho the univalve shell possessed by most gasteropoda. 
 
 43. What arc multivalvc shells? 
 
 44. What gasteropoda are without shells ? 
 
 45. How may it be ascertained, by examining a gasteropod shell, 
 
 whether the inhabitant \vas carnivorous or vegetable- 
 feeding ? 
 
 40. 1 then- any connection between the notches found in certain 
 shells and the carnivorous habits of the animals ? 
 
 47. Describe the " eye-stalks " of a snail. 
 
 IS. < Jive an account of the digestive apparatus. 
 
 49. What is the distinction between the /'u lino-Gasteropoda and. 
 the Brancldo-Gastcropoda? Give examples of each. 
 
 60. How is respiration effected in the J/etcropoda&nd. sea-slugs? 
 
 . r > I . What air-breathing gasteropods live in water ? 
 
 52. What are otoliths t 
 
 53. Show that the larvos of certain gasteropods resemble the 
 
 :i<hilt /Ym>/W<r. 
 
 64. Why are the I ^niirHihrtiiicluata SO called ? 
 [>f>. (Jive examples of this class, distinguishing between marine 
 
 and fresh-water species. 
 
 56. By what other names is this class known? 
 
 57. Distinguish the bivalve shells of the LamdUbranchiata from 
 
 those of the Brochiopoda* 
 
 58. Explain the following terms: Umbo, inequilateral, ci/ui- 
 
 lateral, c^uivalvc, Icmjdi, breadth, pvxl.n'ivr side, anterior 
 aide, /i.sv, /'//>, l'njiiicnt, mr//7m/r. 
 
 .7.). How ai-e the valves opened and shut? 
 
 ('(). Why does a dead oyster always gape? 
 
 (il. What is meant by the " foot" of a lamellibranch ? 
 
 02. Explain the terms : Pallial line, pallial sinus, muscular im- 
 pressions. 
 
 63. Describe the digestive apparatus. 
 
 64. What are palpi ? 
 
 (>;"). What is believed to be the nature of the food? 
 
 66. Describe the heart and circulatory organs. 
 
 (>7. I Tow is respiration ellccted ? 
 
 (IS. Describe the gills. 
 
 lil). 1 1 o w are respiration and sustentation connected in this class? 
 
 70. What lamellibranchs possess breathing siphons? 
 
 71. 1 >escribe the nervous system and the organs of sight ? 
 7-. (live examples of sessile Ittuiellibranclis. 
 
QUESTIONS. 123 
 
 73. F.y what moans are the fry of the oyster removed to a 
 
 distance from tin; parent lied ? 
 7-1. K\ plain the IITIII /irttc/t'm/mdtt. 
 7-"). Give < \.-inip!' B of this class. 
 70. (Jive an account of the distribution in time of the Dnn-ti'"^ 
 
 ppda, 
 
 77. What is their usual habitat? 
 
 78. Dr:-;cribi: tin; bradl i' >pod .shell. 
 
 7i>. I low are the valves opened and clo.-;ed? 
 
 50. What, is \.\\<>. /><:/nncle? 
 
 51 . Describe the til-nix, and state u hat is their supposed function. 
 Si'. (Jive ;m account of their di;.: st ive apparatu.j. 
 
 s;;. \Vhat is known of the circulation? 
 
 84. What is meant by the afrial M/atem ? 
 
 S."). \\'liat is ilie nature of the respiration ? 
 
 SU. ( live an account of the nervous system. 
 
 87. Into what two gro-.ips are they divided? 
 
 88. Give an account of the Tuiticuta or Axcidloida. 
 S!. Ivx plain th<-:^e terms. 
 
 t(). Distinguish between simple, social, and compound aseidians. 
 HI. DI -;<]]!)(; the text, and state what vegetable substance it 
 
 contains. 
 
 !>_>. ( Jive- an account of the In-nncli'ml ynr and the atrlal chamber. 
 !>;*. \Vhat is the nature of the circulation? 
 
 1M-. How is th<; blood purilicd ? 
 
 I)."). What is the nature of the nervous system ? 
 
 !)(>. Show that the larvie in some groups differ widely from the 
 
 ' animals. 
 
 1)7. What are Hie /V//;.on? 
 
 l)S. (live examples. Why are they sometimes called zoophytes? 
 
 !W. (Jive a general description of these animals. 
 
 100. How do they differ from the Ifydrozoa? 
 
 101. What is meant by gemmation? 
 
 102. What are avicular'i<i .' 
 
 103. K.\ plain i>o////>'lc, />o/>/-f,</r'uim t cctocyst, endocyst. 
 
 104. What is the nature of the digestive apparatus ? 
 
 105. 'What i.s known of the circulation and respiration? 
 
 106. (Jive an account of the nervous system. 
 
 107. How are new colonies funned? 
 
124: ZOOLOGY. 
 
 CHAPTER V. 
 
 CCELENTERATA AND PROTOZOA. 
 
 SUB-KINGDOM VI. Ccslenterata. 
 CLASS 1. Actinozoa. 
 
 178. The Actinozoa (Gr. aktis, a ray ; zoon, an animal) 
 is the highest class of the Ccelenterata. It includes the 
 sea-anemones, the corals, the sea-pens, and some of the 
 jelly-fishes. These animals are exclusively marine. 
 
 The Actinozoa are defined as ccelenterate animals, in 
 which the 'mouth leads to an alimentary canal, which, in- 
 stead of being continued through the body, and terminating 
 at the exterior, communicates by a wide aperture with the 
 general cavity of the body. This canal is separated from 
 the body walls by a space, which is divided into compart- 
 ments by a series of vertical partitions called mesenteries 
 (Gr. mesos, the middle ; enter on, intestine). To the sur- 
 faces of these mesenteries the ovaries and sperm cells are 
 attached. 
 
 179. The body consists of two separate layers an outer 
 and an inner. The outer is termed the ectoderm (Gr. ectos, 
 without ; derma, skin), and the inner the endoderm (Gr. 
 endon', within; derma, skin). The interior of the body 
 is filled with fluid, in which a circulation is promoted by 
 the cilia that line the inner walls of the endoderm. The 
 only digestive organ is a stomach, in the form of a tube, 
 which can only communicate with the exterior through 
 the mouth. ]STo heart or circulatory organs have been 
 discovered in any member of this class. In one group 
 only ( ' Ctenopliora) is there any trace of a nervous system. 
 The sexes are often united in the same individual. Some 
 are simple, others are compound. Colonies are formed 
 by budding, or by self-division of a single individual, as 
 
CG5LENTERATA ACTINOZOA. 
 
 125 
 
 in the Polyzoa. The individual members of these colonies 
 are called polypes (Gr. polus, many; pous, foot) ; the 
 entire colony, the actinosoma (Gr. aktis, a ray; soma, a 
 body); the common fleshy structure, the ccenosarc (Gr. 
 koinos, common; sarx, flesh). The corals are fixed; the 
 sea-anemones are capable of shifting their position very 
 slowly; the Ctenopkora can swim with facility by the 
 action of their 
 cilia. The sea-ane- 
 niones and Cteno- 
 pliora are destitute 
 of any hard struc- 
 ture. Some groups 
 secrete a horny, 
 others a calcareous 
 skeleton, which 
 is called coral. 
 
 180. The com- 
 mon sea-anemone 
 (actinia) forms a 
 good example of 
 this class. It is a 
 simple animal, the 
 actinosoma consist- 
 ing of a single po- 
 lype. It may be 
 found on the sea 
 shore, in almost any 
 rocky pool. When 
 the tide is out, it 
 looks like a little 
 lump of red flesh; 
 but, when it gets 
 covered with sea 
 water,its true shape soon appears. It is of a cylindrical 
 form, and is firmly, but not permanently, attached to a 
 rock by its lower part or base, which acts like a sucker. 
 It is able to move along, at the rate of a few inches a 
 
 Fra 62. SEA-ANEJIOXE, 
 attached to a gasteropod shell. 
 
126 ZOOLOGY. 
 
 clay, somewhat after the manner of a snail, but much 
 more slowly. Opposite the base is the disc, in the 
 centre of which the mouth is placed. The circum- 
 ference of the disc is surrounded by two rows of ten- 
 tacles, arranged alternately in concentric circles. There 
 are sometimes as many as two hundred of these tentacles. 
 They are hollow tubes, communicating with the cavity of 
 the body. The animal is able, by contracting its body 
 walls, to force water into these tentacles, and thus pro- 
 trude them to a considerable length. It has also the 
 power of withdrawing the water, and contracting them. 
 Sometimes the tubes are open at the tips also. These 
 tentacles are the prehensile organs of the animal. They 
 are furnished with those singular weapons called thread 
 cells. Each of these cells consists of a membranous sac, 
 containing a coiled up thread. When the cell is touched, 
 a filament, barbed at the point, and serrated along the 
 edges, is projected from it with sufficient force to pene- 
 trate the tissues of most animals with which it comes in 
 contact. These thread cells are also found in the lining 
 of the alimentary canal, and in the outer integument, 
 which is of a soft leathery structure. 
 
 The mouth leads into a tubular stomach, which is not 
 followed by an intestine, but opens below into the general 
 cavity of the body by a wide aperture. The indigestible 
 portions of the food are ejected out of the mouth. The 
 alimentary tube terminates about half-way between the 
 mouth and the base. The intervening space, between 
 this tube and the body walls, is divided by a number of 
 vertical partitions, or mesenteries, into compartments. 
 Some of the partitions, which originate in the body wall, 
 do not reach the whole way to the outer lining of the 
 alimentary tube. These compartments communicate with 
 the open bases of the tentacles. To the walls of the 
 mesenteries the reproductive organs are attached. The 
 sea-anemones have generally the sexes in distinct in- 
 dividuals. The embryo is a minute oval body, and is able 
 to swim about freely by the action of its cilia. 
 
CCELENTERATA ACTINOZOA. 
 
 127 
 
 181. The "reef-building corals" differ from the sea-ane- 
 mone mainly in having the power of secreting within their 
 tissues a skeleton composed of carbonate of lime. This 
 skeleton is termed the corallum. Tn its simplest form it 
 consists of a calcareous cup. of a cylindrical or conical 
 
 FIG. 53. FUXGIA, a simple form of Coral, inhabited by a single Polype only. 
 
 form, with radiating lamellae called septa. Some of these 
 septa reach and others fall short of a central column 
 which is generally present. The outer cup or theca (Gr. 
 theke, a sheath), is secreted by the inner surface of the 
 endoderm of the body wall ; the septa, by the radiating 
 partitions or mesenteries. The corallum is thus a cast 
 in carbonate of lime of the polype that forms it. 
 
 The reef-building corals are generally compound animals, 
 forming colonies by budding and sell-division. New 
 colonies are formed by minute ova, which are produced 
 at certain seasons. Like the embryos of the sea-anemone, 
 they are able to swim about by the action of their cilia. 
 They are united by a common living substance, or 
 
128 ZOOLOGY. 
 
 COBHOSarc. "They constitute a true republic, in which 
 each citizen, whether consciously or not, is compelled to 
 support the general state, by which he himself exists." 
 (Haugkton). The ccenosarc secretes a common calcareous 
 structure, which unites all the cups into one strong mass. 
 Coral, formed thus ivithin the tissues of the animal, is 
 called sclerodermic (Gr. skleros, hard; derma, skin). 
 The septa of modern corals are always multiples of Jive 
 or six; while, in extinct corals (Rugosa), they are 
 uniformly multiples of four. 
 
 182. Coral Beefs. The coral polypes, small as they 
 are, have been important rock-forming agents in all 
 periods of the world's history. The stony masses formed 
 by them are termed coral reefs. The coral zone extends 
 about 30 on each side of the equator. The reefs are 
 principally found in the Indian Ocean, on the east coast 
 of Africa, and near the shores of Madagascar; in the 
 Persian Gulf, the Red Sea, and the Bay of Bengal ; in 
 the Atlantic Ocean, round the "West India Islands, and 
 the coast of Florida ; they are especially abundant round 
 the islands and continents washed by the Pacific Ocean. 
 The coral animals require a mean annual temperature of 
 not less than 68. On this account they are rare, and of 
 small size, in our seas at present. No coral reefs are 
 found either along the west coast of Africa, or the 
 corresponding coast of South America, on account of the 
 cold currents which flow in these places. These reefs 
 assume three principal forms. 
 
 183. (1.) Fringing Reefs, which skirt the shores of 
 continents and islands. These reefs have been constructed 
 in water comparatively shallow, and are generally not far 
 from land. 
 
 184. (2.) Barrier Beefs are distinguished from fringing 
 reefs, by occurring at a considerable distance from the 
 nearest land. They are also surrounded by deep water. 
 The great barrier reef on the north-east coast of 
 Australia, is a notable example of this class. This reef 
 is about 1,100 miles long, and 30 broad on an average, 
 
CCELEXTERATA ACTIXOZOA. 129 
 
 Its distance from the Australian coast is about 30 miles. 
 The sea on the inner side is 300 feet deep ; in some places 
 outside it is 1,800 feet. Sometimes a barrier reef sur- 
 rounds an island, which on this account is called a lagoon 
 island, the intervening water being called a lagoon. 
 
 185. (3.) Atolls are rings of coral, surrounding a cen- 
 tral lagoon, in which there is no island. They are usually 
 pierced by several openings, and form excellent natural 
 harbours. As the coral animal cannot subsist in fresh or 
 brackish water, these gaps are believed to have been 
 originated by rivers which once flowed from the island 
 round which the polypes began to build. There are 
 several groups of atolls both in the Indian and Pacific 
 Oceans. The ring of coral is sometimes 90 miles in 
 diameter, but is seldom more than a quarter of a mile 
 broad. Although only raised a few feet above sea level, 
 many of them have human inhabitants. 
 
 The coral animal, it is evident, could never raise a reef 
 above the sea level, as it cannot exist out of the water. 
 The reefs are raised by the action of the waves which 
 detach masses of rock, and pile them up an island in 
 the course of ages is thus formed. The interstices of the 
 masses are gradually filled up by calcareous sand, also 
 washed off by the action of the waves, and the whole 
 mass is cemented together by water containing carbonate 
 of lime in solution. 
 
 A coral reef, as has been stated, sometimes extends 
 downwards as much as 1,800 feet, and it was formerly 
 believed that the coral polypes commenced to build at 
 these depths, and gradually raised their structures until 
 they reached the surface. Darwin has proved the incor- 
 rectness of this theory, and has shown that the coral 
 animals cannot live at a greater depth than from 15 to 
 30 fathoms. He accounts for the occurrence of coral 
 reefs at greater depths, by the gradual subsidence of the 
 gea bottom. He believes that all coral reefs were origin- 
 ally constructed in shallow water, near the shore of some 
 island or continent; that is, they were once in the 
 
 15 a j 
 
130 
 
 ZOOLOGY. 
 
 of fringing reefs. The sea bottom gradually sank, but 
 the coral animals kept pace with this subsidence, building 
 upwards, so as to keep their structure nearly as high as 
 the sea level. The island, surrounded by a reef, ulti- 
 mately disappearing beneath the waves, the ring of coral 
 would be converted into an atoll, which alone remains to 
 show where an island had been. When a barrier reef sur- 
 rounds a lagoon island, it is evident that if subsidence 
 goes on the island will ultimately disappear, and the sur- 
 rounding reef be converted into an atoll. Darwin 
 believes, that in those areas where fringing reefs are 
 found, the land is either rising or stationary ; and where 
 atolls and barrier reefs occur, the sea bottom is subsiding. 
 
 FIG. 54. STRUCTURE AND DEVELOPMENT OF CORAL. 
 
 A, Branch of Red Coral; a, the calcareous axis, constituting the Red Coral 
 of commerce; some of the polypes are expanded, and others contracted. B, 
 ciliated larva of coral. C, larva developed, ready to fix itself and form a new 
 colony. 
 
 186. The red coral, found in the Mediterranean and 
 other warm seas, is an example of what is called sclero- 
 basic (Gr. scleros, hard; basis, foundation) coral. This 
 
CCELENTERATA ACTINOZOA. 
 
 131 
 
 coral is branched like a tree, and was formerly believed 
 to belong to the vegetable kingdom. There is a rind of 
 fleshy matter which surrounds a central stony stem, just 
 as a tree is invested by its bark. This fleshy matter is 
 the crenosarc, and in it the polypes are embedded. The 
 polypes are each furnished with eight leaf-like tentacles, 
 which are fringed at the edges. The living rind secretes 
 the internal skeleton, which is composed mainly of car- 
 bonate and phosphate of lime. This skeleton, although 
 it is within the ccenosarc, taken as a whole, is really out- 
 side the polypes that is, it is not secreted within their 
 tissues, as in the sclerodermic corals. If a number of 
 sea-anemones were united together into a colony, and 
 placed round a central stem, having their bases in contact 
 with it, and -their discs outside; it is evident that, al- 
 though this stem would be within the 
 combined substance of the community 
 as a whole, it would be outside, or at 
 the base of each individual polype. In 
 some of the sclerobasic corals the 
 skeleton is horny, in others it consists 
 of alternate joints of calcareous and 
 horny matter. 
 
 The tentacles are fringed, and these, 
 as well as the mesenteries, are always 
 some multiple of four. 
 
 Closely allied to the red coral are 
 the dead men's fingers, and virgularia 
 or sea-rods, both of which are met 
 with in British seas. 
 
 187. The Ctenophora (Gr. kteis, a 
 comb ; phero, I carry) are a free-swim- 
 ming, gelatinous group of actinozoons, 
 which are popularly placed among the 
 jelly-fishes. They are usually found on the surface of 
 the ocean, far from land, swimming rapidly Jby the action 
 of the cilia with which they are provided. They are very 
 abundant in the northern seas, and form the food of several 
 
 Fia.55. BEROE, ONE OF 
 TIJE CTENOPHORA. 
 
132 ZOOLOGY. 
 
 whales. Some of the commonest forms are melon-shaped, 
 but not bigger than a boy's marble. The cilia are arranged 
 in eight bands, or ctenophores, extending from the upper to 
 the lower extremity of the body. They are also furnished 
 with a pair of long-fringed tentacles, which can be com- 
 pletely retracted within sacs. These animals are destitute 
 of any skeleton or hard parts. They contain a little 
 mass of matter, believed to be nervous, from which a few 
 filaments proceed. This is the only trace of a nervous 
 system found in the Ccelenterata. Some species of 
 Ctenophora are luminous at night. 
 
 CLASS 2. Hydrozoa. 
 
 188. The Hydrozoa (Gr. hudra, a water dragon; zoon, 
 an animal) are ccelenterate animals, in which the digestive 
 sac is not separated from the body cavity by any interven- 
 ing space as in the Actinozoa, the alimentary canal and the 
 somatic cavity forming one continuous tube. The repro- 
 ductive organs are external) being attached to the outer 
 surface of the body wall. 
 
 189. This class includes the fresh-water hydra, Sertu- 
 laridse or sea-firs, the Corynidss or club-hydras, the 
 LucernaridSB or lantern-hydras, and the Medusae or 
 jelly-fishes. Some are simple, others form colonies by 
 budding or self-division. They are cellular in structure, 
 and the body consists of two layers, ectoderm and endo- 
 derm. The mouth is surrounded by tentacles, by means 
 of which the animals seize their prey. They possess 
 thread-cells, which are found in the tentacles, as well as 
 in other parts of the body. The mouth leads into a 
 digestive sac, " the outer wall of which is in direct con- 
 tact with the water in which the animal lives." This sac 
 leads by a wide aperture to the general cavity of the body, 
 which is merely a continuation of the digestive tube. 
 Thus, if a vertical section be made of a hydrozoon, only 
 a single tube will t> gut through j whereas^ if a simitar 
 
CGELENTER ATA HYDROZOA. 133 
 
 section be made of an actinozoon, a double tube will have 
 been dissected. " If you could suppose the stomach of a 
 hydrozoon thrust into that part of the body with which 
 it is continuous, so that the walls of the body should rise 
 round it and form a sort of outside case, containing a 
 prolongation of the general cavity, the hydrozoon would 
 be converted into an actinozoon.." (Huxley). 
 
 190. In the compound Hydrozoa, the individual zooids 
 which form a colony are denominated polypites, to dis- 
 tinguish them from the polypes in the Actinozoa, and 
 the polypides in the Polyzoa. The entire body of a 
 hydrozoon, whether simple or compound, is called the 
 hydrosoma (Gr. hudra-, and soma, body) ; the substance 
 which is common to the various polypites in a colony, the 
 coenosarc. 
 
 The compound Hydrozoa (sertularia, &c.,) were formerly 
 placed along with the Polyzoa, both of which were 
 popularly called Corallines. These two groups are, how- 
 ever, widely different in internal structure. 
 
 191. (1.) The Polyzoa possess an alimentary canal, 
 which is completely shut off from the general cavity of 
 the body, and communicates with the exterior by an anal 
 opening. The alimentary tube, in the Hydrozoa, opens 
 directly into the body cavity, and is not separated from 
 the body walls. 
 
 (2.) The Polyzoa have a distinct nervous system. To 
 nerves have been found in any hydrozoon. , 
 
 (3.) In the Polyzoa the reproductive organs are internal. 
 In the Hydrozoa they form " outward processes of the 
 body wall, and are directly in contact with the surround- 
 ing medium." 
 
 192. The fresh-water hydra may be taken as an example 
 of this class. This animal is common in ponds, and may 
 be found attached to the stems of aquatic plants. In its 
 contracted state it is a little mass of green jelly, about 
 half the size of a pea. If this little gelatinous ball is 
 placed in a glass of water it will manifest its true form. 
 The body is a tube, about half an inch long, and not much 
 
134 
 
 ZOOLOGY. 
 
 thicker titan a sewing thread. It consists of two layers 
 the outer, the ectoderm ; the inner, the en do derm. Its 
 
 base is furnished with 
 a sucker by which it 
 is able to attach itself 
 to some solid object. 
 The attachment, how- 
 ever, is not permanent, 
 as it is able to change 
 its position when it 
 wishes to do so. Its 
 mouth is surrounded by 
 a number of tentacles 
 which it has the power 
 of lengthening or short- 
 ening with great facil- 
 ity. When completely 
 retracted, they have the 
 appearance of little 
 warts of j elly. The ten- 
 tacles are hollow tubes, 
 and are formed by pro- 
 
 FIG. 5G. FRESH-WATER HYDRA (enlarged). 
 It is attached to a fragment of duck- weed, 
 and comprises three individuals, of which 
 the largest has the tentacles more expanded 
 than the others. The black lines represent 
 the digestive tube. The individual to the 
 right has been tied by a thread to show how 
 the animals may be multiplied by division. 
 Below are two detached individuals sup- 
 posed to be formed in this way. 
 
 longations of both the 
 
 ectoderm and endoderm. 
 They communicate at 
 their bases with the 
 cavity of the body. It 
 is very greedy, and 
 any small animal which 
 it seizes with its tenta- 
 cles is soon benumbed by the thread cells with which 
 they are furnished. In the brown hydra the tentacles 
 are sometimes eight inches long. 
 
 These animals feed on minute worms, insects, Kotifera, 
 water-fleas, and other small Crustacea. The mouth 
 leads into a digestive tube, which opens into the general 
 cavity of the body. This cavity contains water, with 
 which the particles of food are mixed. The indigest* 
 
CCELE STERATA HYDROZOA. 135 
 
 ible portions of the food are expelled through the 
 mouth. 
 
 If a hydra is cut into two pieces, one portion will 
 develop a new trunk and base, the other will soon, 
 throw out new tentacles. In this way two perfect 
 animals may be formed from a single individual. If 
 it be cut into half a dozen or more pieces, each piece 
 will develop the wanting parts, and will grow into an 
 animal as perfect as the original. It may even be turned 
 inside out without seeming to suffer any inconvenience. 
 
 193. Reproduction, in the hydra, is effected in two 
 ways by budding, and by ova. During the summer 
 season, little wart-like buds appear on the surface of the 
 body. These increase in size, and a mouth is formed, 
 which is soon surrounded by a circle of tentacles. In 
 its imperfect state, it receives nutriment from the 
 stomach of the parent; but when the tentacles are formed 
 it begins to procure food for itself, and the channel of 
 communication becomes closed up. When it has ar- 
 rived at maturity, it detaches itself, and becomes 
 independent. 
 
 In autumn, ova and sperm cells are formed in little 
 elevations of the outer surface of the body wall. These 
 are deposited simultaneously in the water, and the 
 fertilized ova remain in the bottom of the pond, until 
 the next spring, when they are hatched. Very few 
 hydras, it is believed, live through the winter. The 
 embryo, at first, swims about by the action of the cilia 
 with which it is covered. It soon fixes itself by one 
 extremity, loses its cilia, and obtains a mouth and 
 tentacles. 
 
 194. The Corynidse (Gr. korune, a club), or club-hydras, 
 are marine animals, with the exception of one genus 
 which inhabit fresh water. Some of them are simple, 
 and resemble the fresh- water hydra in structure; but 
 they are permanently attached to a solid object. The 
 greater number are compound, being united by a thread 
 of jelly-like flesh. These are generally provided with 
 
13S ZOOLOGY. 
 
 a chitinous or horny covering, denominated the poly- 
 pary. This covering does not enclose the polypites in 
 the club-hydras, as it terminates at their bases. 
 
 195. The Tubularia is an example of this group. It 
 consists of a number of horny tubes which are attached 
 to stones or shells. These tubes are not branched, but 
 are often interlaced with one another. A single polypite 
 is situated at the extremity of each. The tubes are filled 
 with a red jelly-like substance. The polypites are also 
 of a red colour. They are provided with two sets of 
 tentacles, one short row being placed round the mouth, 
 and a longer row near the base. 
 
 196. Development. In the compound Hydrozoa, the 
 buds, instead of being separated from the original stock, 
 as in the fresh-water hydra, remain permanently attached 
 to it, and soon begin to develop other buds. In this way 
 a colony is formed. There are often two different sorts 
 of zooids. One kind are without reproductive organs, 
 their function being merely to procure food for the 
 colony. These are denominated alimentary zooids, 
 and taken collectively, are called the trophosome (Gr. 
 trepho, I nourish ; soma, body). These go on increasing 
 by budding; but, at a certain stage in the life of the 
 colony, a second set of buds is produced, furnished with 
 ova and sperm cells. These buds are termed gonophores 
 (Gr. gonos, offspring ; phero, I bear). These gonophores 
 are often much larger than the alimentary zooids, and are 
 of three different kinds. 
 
 197. One kind consists of a protuberance formed by the 
 ectoderm and endoderm. They are closed without, but 
 maintain an internal connection with the ccenosarcal 
 fluid. They produce fertile ova. 
 
 198. A second kind are bell-shaped discs, which are 
 attached to the polypary by the base, the cavity of the 
 bell being turned outwards. There is a kind of handle 
 within the cavity of this bell, occupying the place of the 
 clapper, and termed the manubrium (Lat. manubrium, a 
 tandle.) From the point where the manubrium is 
 
CCELENTER ATA S YDROZO A. 13? 
 
 attached to the disc, four canals proceed to the margin 
 of the bell. All these open into a circular canal which 
 surrounds the margin. The ova and sperm cells are pro- 
 duced either in these canals or in the manubrium. 
 
 199. The third kind are similar to the preceding, but 
 become detached and lead an independent existence, 
 swimming about by the alternate contraction and ex- 
 pansion of their discs. A mouth is developed at the 
 outer extremity of the manubrium, and the polypite be- 
 comes self-feeding. The mouth of the bell is closed, with 
 the exception of a central aperture, by a delicate mem- 
 brane called the veil. A number of tentacles are 
 produced round the margin. As soon as fertile ova are 
 developed, the creature dies. 
 
 These bell-shaped gonophores are commonly called sea- 
 jellies or sea-medusa, and were formerly believed to be 
 distinct animals. The margin of the bell in some groups 
 is adorned with a number of bright spots, which are 
 supposed to be either organs of sight or hearing. These 
 are called the naked-eyed medusae. They vary much 
 in size, some of the smaller kinds being not larger than 
 the head of a pin. Many of them have brilliant colours, 
 and are very beautiful. They are described by the late 
 Professor Edward Forbes as " gorgeous enough to be the 
 diadem of the smallest of the sea-fairies, and sufficiently 
 graceful to be the night-cap of the tiniest and prettiest of 
 mermaids." They are generally phosphorescent, and con- 
 tribute largely to the luminosity of the sea. The ova 
 developed by the medusa?, instead of reproducing animals 
 of the same kind, grow into fixed plant-like organisms, 
 similar to those from which the gonophores were de- 
 tached, thus furnishing an example of what has been 
 called, "alternation of generations;" that is, "an in- 
 dividual is not at all like its mother, but exactly re- 
 sembles its grandmother." 
 
 200. The Sertularidae (Lat. sertum, a wreath), or 
 sea-firs, are more generally known than any of the com- 
 pound Hydrozoa. The polypary is much branched, often 
 
138 
 
 ZOOLOGY. 
 
 resembling a minute fern. They may readily be found 
 011 the sea shore, sometimes attached to the shells of the 
 mussel and oyster. They are all compound animals, and 
 are confined to the sea. 
 
 201. In the CorynidcB, the horny polypary merely 
 
 extends to the base 
 of the polypites; but 
 in the Sertularidse, it 
 is prolonged into lit- 
 tle cups (Hydrothe- 
 cce), within which the 
 polypites can with- 
 draw themselves. 
 
 The zooids closely 
 resemble the hydra 
 in structure. At the 
 lower extremity of 
 the body cavity, there 
 is a minute opening 
 which communicates 
 with the hollow tubes 
 of the polypary. These 
 tubes are filled with 
 a jelly-like fluid, 
 which connects all 
 the polypites togeth- 
 er into one living 
 mass. To this fluid 
 each individual poly- 
 pite contributes nu- 
 Fm. 57. CAMPANULARIA (magnified). triment, through the 
 
 Allied to Sertularia. Some of the polypites aperture at the base 
 are retracted, others expanded. ^ ,-, 11 , 
 
 of the body cavity. 
 
 It is kept in constant circulation, probably by the action 
 of cilia. 
 
 The ordinary polypites, or alimentary zooids, are 
 not provided with reproductive organs. At certain 
 seasons of the year, generative buds are formed, which 
 
COELENTEHATA HYDROZOA. 139 
 
 are much larger than the ordinary cups in which the 
 polypites reside. These buds, being destitute of mouth 
 and tentacles, obtain their nourishment from the cceno- 
 sarcal fluid, which permeates the tubes of the polypary. 
 In these cells ova are formed. These, when hatched, 
 become oval-shaped, and swim about for a time by the 
 action of cilia, with which they are covered. At length 
 they attach themselves to some solid object, lose their 
 cilia, and form fresh colonies by budding. In the sertu- 
 larians, the generative buds are not detached, as in the 
 club-hydras. 
 
 The extinct Graptolites, found so abundantly in the 
 Silurian rocks, closely resemble the Sertularia. It is 
 believed, however, that they were free-swimming, instead 
 of being permanently attached like the Sertularia. 
 
 202. The LucernaridsB (Lat. lucerna, a lamp), or 
 lantern-hydras, are represented in our seas by one 
 species, which has an umbrella or cup-shaped body of a 
 gelatinous structure. It attaches itself, by the base, to 
 sea-weeds ; but can remove itself at will, like the fresh- 
 water hydra. It is able to swim about, motion being 
 produced by the alternate contraction and expansion of 
 its umbrella. Tufts of short tentacles are placed, at 
 intervals, round the margin of the cup. There is a single 
 polypite in the centre, the mouth of which is surrounded 
 by four lobes. Ova and sperm cells are formed within 
 the body itself, there being no generative buds. 
 
 203. A little animal belonging to this group, about 
 half an inch long, denominated the hydra-tube, from 
 its resemblance to the fresh-water hydra, forms large 
 colonies by budding. The polypites are usually without 
 reproductive organs. In soine cases, the hydra-tube 
 becomes lengthened, and surrounde'd by a number of 
 grooves. These grooves deepen, and acquire notched 
 margins. In this stage, the polypite has the appearance 
 of a pile of minute cups or saucers. The tentacles which 
 originally surrounded the mouth disappear, and a new 
 set sprout out near the baso of the hydra-tube. These 
 
HO ZOOLOGY. 
 
 saucers gradually drop off, and appear as free-swimming 
 medusse. Although originally very small, they soon 
 increase in size, and become, in some cases, of great bulk, 
 measuring seven feet across the disc, with tentacles fifty 
 feet long. These gigantic structures are the sea-blub- 
 bers, sea-nettles, or jelly-fish, so common, in the summer 
 season, round our coasts. 
 
 204. These animals are largely composed of sea water. 
 
 FIG. 58. Aurelia, one of the jelly-fishes. 
 
 Professor Owen has calculated that a jelly-fish, 2 Ibs. 
 weight, does not contain more than 30 grains of solid 
 matter. Some of them are furnished with thread cells, 
 whose barbed points are able to penetrate the humau 
 
CCELEXTERATAHYDROZOA. 141 
 
 skin, as many a bather knows to his cost. The principal 
 mass of the body consists of a bell-shaped disc, or um- 
 brella, from the lower part of which a single polypite is 
 suspended. The mouth of this polypite is surrounded 
 by four long processes, or arms. A number of canals 
 (generally eight) proceed from the extremity of the poly- 
 pite to the margin of the umbrella. Near this margin 
 they are broken up into a great number of tubes, and 
 form a kind of network. All these communicate with a 
 circular canal which runs round the margin of the disc. 
 This margin is furnished with a fringe of tentacles, which 
 are supplied with branches from the circular canal. A 
 number of coloured spots, connected with little sacs filled 
 with fluid, and containing stony particles, are also placed 
 round the margin. These specks are concealed by an 
 expansion of the ectoderm, shaped like a hood. On this 
 account, the name, hidden-eyed medusas, has been ap- 
 plied to this group of jelly-fishes. 
 
 205. The following are the principal points of difference 
 between the hidden-eyed and naked-eyed medusa : 
 
 In the naked-eyed medusae, the cavity of the disc is 
 furnished with a veil ; the radiating canals are usually 
 four in number ; these canals never form a network, and 
 the eyes are always uncovered. 
 
 The hidden-eyed medusas have usually eight canals, 
 which form a network; the eyes are covered, and tha 
 mouth of the disc is not protected by a veil. 
 
 206. The reproductive organs "form a conspicuous 
 cross, shining through the thickness of the disc." After 
 swimming about for a time, they develop fertile ova, and 
 then die. The ova, however, instead of producing gigantic 
 sea blubbers, result in minute hydra-tubes, which form 
 colonies as before. Thus we are furnished with another 
 instance of the " alternation of generations." 
 
142 ZOOLOGY. 
 
 SUB-KINGDOM VII. Protozoa. 
 CLASS 1. Infusoria. 
 
 207. If a quantity of boiling water be poured upon a 
 few stalks of hay, or other vegetable matter, and allowed 
 to stand for a few days : if a drop of this infusion be then 
 taken and examined by a microscope, it will be found to 
 contain a multitude of minute creatures, moving about 
 with great agility. A like result will be produced by 
 placing the vegetable substance in a glass of water, and 
 exposing it for a few days to the rays of the sun. These 
 animals have been called Infusoria, because they were 
 first met with in vegetable infusions. The early ob- 
 servers included the Eotifera in this class ; but, as these 
 are much more highly developed animals than the In- 
 fusoria, they have now been placed in the sub-kingdom 
 Annuloida. 
 
 208. The animals produced at first are called monads, 
 and are extremely small. " If arranged side by side 
 in contact with each other like the beads of a necklace 
 twelve thousand of them could be placed within the 
 length of a single inch." If the infusion be allowed to 
 remain for some time longer, fresh forms will be produced, 
 some of them considerably larger than the monads. 
 
 The Infusoria are not confined to infusions of animal 
 or vegetable matter, as they abound in stagnant water 
 everywhere, and are even found in the sea. 
 
 They may be defined as Protozoa, which possess a per- 
 manent mouth, and short gullet, which terminates in the 
 central mass of sarcode. Their bodies consist of three dis- 
 tinct layers, the outer one being generally furnished with 
 cilia. They differ from the Ehizopoda, also, in not having 
 the power of protruding pseudopodia. 
 
 209. Some of the Infusoria are free swimming, others 
 are attached to aquatic plants by a slender stalk. Para- 
 mcEcium (Gr. parameTces, oblong) may be taken as an 
 
PROTOZOA INFUSORIA. 143 
 
 example of the unattached groups. It is in shape some- 
 what like a slipper, and is covered with minute cilia, 
 which are kept constantly in motion. These cilia enable 
 the animal to move rapidly through the water, and also 
 bring a supply of minute particles of food to the mouth. 
 The outer covering of the body is a delicate membrane, 
 called the cuticle. Beneath this there is a layer of 
 somewhat firm jelly, which has been termed the cortical 
 (Lat. cortex, bark) layer. This passes gradually into a 
 semi-fluid mass which occupies the whole interior of the 
 body. No definite structure has been detected in any of 
 these layers. 
 
 There is a funnel-shaped mouth, which is succeeded by 
 a short tube, lined with the cuticle. This tube opens 
 directly into the internal sarcode, and conveys such 
 particles of food, mixed with globules of water, as the 
 currents produced by the cilia may have brought. The 
 name Polygastrica (Gr. polus, many ; gaster, stomach), was 
 applied to the Infusoria by Ehrenberg, because he believed 
 these minute globules of water to be so many stomachs. 
 Indigestible particles pass out by an opening situated 
 near the mouth. This anal aperture does not seem to be 
 connected with any tube corresponding to an intestine. 
 
 At one or two points there are certain clear spaces in 
 the cortical layer which open and close alternately. 
 These are denominated contractile vesicles. When 
 expanded, they appear to be filled with a clear fluid, which 
 is probably water. When contraction takes place, this 
 iluid disappears. Some observers are of opinion that 
 these vesicles communicate with the external medium, 
 and are connected with canals which radiate through the 
 central sarcode. It is probable that this apparatus is of 
 a respiratory nature, bearing some analogy to the water 
 vascular system of the Annuloida. 
 
 A little oval mass has been observed in another part 
 of the cortical layer, to which the name nucleus has 
 been given. Besides this, there is a smaller round mass 
 which has been called the nucleolus. These are 
 
144 
 
 ZOOLOGY. 
 
 believed to be generative organs, the nucleus being an 
 ovary, and the nucleolus a mass of sperm cells. It has, 
 therefore, been concluded that these animals are herma- 
 phrodite, reproducing their kind by fertile ova. 
 
 210. Another mode of reproduction is termed fission 
 (Lat. fissus, a cleft), or self-division. The body of a Par- 
 amcecium splits into two parts, each of which becomes an 
 independent being. A well fed animal of this group has been 
 observed to divide in this manner every twenty-four hours. 
 
 211. The Vorticella (diminutive of Lat. vortex, a 
 whirlpool), or bell-animalcule, may be taken as the type 
 of the fixed forms of Infusoria. It may be found attached 
 to the stems of the duck-weed, and other aquatic plants. 
 To the naked eye a group of these animals gives a musty 
 appearance to the stem of the plant on which they are 
 located. When viewed by a microscope they appear as 
 
 beautiful little bells or 
 vases, attached to stalks 
 which are eight or nine 
 times their own length. 
 This stalk is a tube, and 
 the animal has the power, 
 when alarmed, of contract- 
 ing it into a spiral form 
 by means of a filament 
 which passes through it 
 in a longitudinal direction. 
 At the margin of the 
 bell there is a projecting 
 rim which surrounds a 
 circular space called the 
 FIG. 59.-VORTICELLA. di sc< This disc is separ- 
 
 ated from the rim by a groove, and is furnished at its 
 outer margin by a fringe of cilia, forming a spiral line 
 which is carried one or more times round the circumfer- 
 ence. The animal has the power of retracting the diso 
 with its ciliated fringe into the interior of its body. 
 The layers of the body are similar to those found in 
 
PROTOZOA INFUSORIA. 1 45 
 
 Paramoccium. There is an outer cuticlo, a cortical 
 layer, and a central mass of sarcode. The cortical layer 
 contains a contractile vesicle and a nucleus. 
 
 The mouth is situated near the edge of the disc, the 
 fringe of cilia being continued into the oesophagus. The 
 particles of food brought by the cilia, as well as the entire 
 contents of the body, perform a slow rotatory movement 
 through the interior. Indigestible particles are ejected 
 through an anal opening, situated near the mouth. 
 
 212. Development. Reproduction in Yorticella is 
 effected by fission, gemmation, and encystation. The 
 first of these modes is thus described by Gosse : 
 
 " One of the full grown bells begins to alter its form, 
 becoming first globular, then a flattened sphere ; presently 
 a slight notch or depression is observed in the upper part 
 of the outlilie, and it soon becomes apparent that this 
 depression is a constriction extending all round, which 
 gradually becomes deeper and more marked. As the two 
 divisions become more separate, each assumes an oval 
 form, united at length to its fellow only at the base. At 
 this time the motion of the cilia is plainly visible, form- 
 ing a circle in each within the body, near the summit. 
 As the process goes on, the connection between the two 
 is reduced to a mere point, and they become capable of 
 separate motion, so far as to diverge and look in opposite 
 directions ; the point of union being the common stem. 
 At this stage we may observe that the bell which is des- 
 tined to remain is open at the top, within which the 
 ciliary waves are chasing each other in continuous wheels, 
 the other bell being closed at the summit. 
 
 " But on the latter, which is ultimately to be thrown 
 off, a new and highly interesting phenomenon appears. 
 The cilia, which before the division had played around 
 the mouth, have become obliterated, probably by absorption; 
 the orifice at that extremity has closed up permanently, 
 for this is to be the base of the new animal ; and a new 
 bell-mouth and a new wheel of cilia are to be formed at 
 the opposite end, which at present remains attached to 
 15 E. K 
 
146 ZOOLOGY. 
 
 the common stem. The first indication we can detect of 
 this new formation is a very slight movement in the 
 water, a little quivering around what we must yet call 
 the basal part. Presently there appear waved hairs, 
 which seem very flexible, and the motion of which re- 
 sembles that of a fringe of loose silk moved through the 
 water, an action very different from the regular waves of 
 perfect cilia. These waving hairs increase rapidly in 
 length, and in the vigour and rapidity of their undula- 
 tions, which gradually become decidedly rotatory, produc- 
 ing at length strong currents in the surrounding water, 
 and imparting a tremulous motion to the whole bell. 
 
 "It is evident now that the separation is imminent, 
 for the minute point of connexion cannot long withstand 
 the rushing current of those rotatory paddles. At length 
 the bell suddenly shoots away, gliding with great swift- 
 ness through the water, borne by its numerous paddles, 
 and whirls about fora while in a headlong giddy manner. 
 At length it chooses a place of rest, becomes stationary, 
 fixes itself by that end which had formerly been the 
 mouth, but is now closed up, and presently begins to rise 
 by the development of a slender stalk which, though 
 minute at first, increases in length until it attains the 
 original dimensions." 
 
 In reproduction by gemmation, the bell is not split in 
 two, a bud being produced near its extremity by the 
 expansion of the cortical layer. This bud is at first 
 nourished by the parent animal, but when it obtains its 
 circle of cilia it detaches itself, and swims about for a 
 time, then develops a stalk, and becomes fixed as before. 
 
 213. At certain seasons the Yorticella coats itself with 
 a cyst (Gr. kustis, a bladder) of gelatinous matter, the 
 cilia and stalk disappearing. After a time the cyst 
 bursts, and a number of germs are set free, which, after 
 swimming about for a time, develop stalks and become 
 bell-animalcules like the original. This is denominated 
 reproduction by encystation ; whether it is sexual or 
 otherwise, has not been ascertained. 
 
PROTOZOA EHIZOPODA. 
 
 147 
 
 CLASS 2. Rhizopoda. 
 
 214. The Rhizopoda (Gr. rhiza, a root; poda, feet) may 
 be defined as sarcode animals destitute of a- mouth) and 
 having the power of sending out pseudopodia. 
 
 To this class belong the Amoeba, the Foraminifera, the 
 Eadiolaria, and Spongida, each of which will require a 
 separate description. 
 
 215. (1.) The Amoeba (Gr. amoilos, changing), or Proteus 
 animalcule, is a microscopic animal commonly met with 
 in stagnant ponds. It is the simplest of all animals. It 
 consists of a little mass of jelly-like sarcode, resembling 
 the white of an egg, or rather a drop of gum Vater. It 
 is destitute of all those organs which are usually consi- 
 dered to be essential to life. There is no mouth or 
 digestive apparatus, no heart, no circulatory organs, no 
 respiratory organs, no nervous system. The animal is 
 
 FIG. 60. AA , Different forms of Amoeba ; B, Amoeba difflugia, having the 
 pseudopodia protruded from one extremity only; C, Milliola, one of the For- 
 aminifera. in which the pseudopodia are protruded only from the mouth of the 
 shell. 
 
 able to use any part of its body as a hand or a foot, and 
 to extemporize a mouth and alimentary canal anywhere 
 that may best suit its exigencies at the time. 
 
148 ZOOLOGY. 
 
 It constantly alters its shape, pushing out from various 
 parts of its substance blunt, finger-like processes, deno- 
 minated pseudopodia (Gr. pseudos, false; poda, feet). 
 These pseudopodia procure food for the animal, and en- 
 able it to change its position slowly. When a pseudo- 
 podium comes in contact with some particle of animal or 
 vegetable matter, it surrounds it with its jelly. The rest 
 of the sarcode flowing up to this point, the food is in- 
 closed in the substance of the body, where it is digested. 
 It soon pushes out another process in a different direc- 
 tion, when a similar result follows. Sometimes six or 
 eight pseudopodia are sent out at the same time. In this 
 way food is procured, and locomotion effected simulta- 
 neously. As it is destitute of excretory organs, indiges- 
 tible particles are pushed out through the sarcode. 
 
 The outer layer of the body, termed the ectosarc (Gr. 
 ecto, without ; sarx, flesh), is a little more solid than the 
 interior, which is called the endosarc (Gr. endo, within). 
 
 Each particle of food carries with it a little globule of 
 water. These globules are visible in the interior of the 
 animal, and were formerly believed to be stomachs. A 
 contractile vesicle, similar to that observed in the Infu- 
 soria, has been found in the Amoeba. It is filled with 
 some clear fluid, and contracts and expands at pretty 
 regular intervals. There is also a nucleus, which some 
 suppose to be connected with reproduction : but there is 
 no certain knowledge on this point. 
 
 The most usual mode of reproduction which has been 
 observed is by fission, or self-division. The animal in 
 certain cases splits into two parts, each of which becomes 
 a distinct individual. Occasionally, a detached pseudo- 
 podium is developed into a separate animal. 
 
 216. (2.) The Foraminifera (Lat. foramen, a hole; 
 feroy I bear) differ from Amoeba in being covered with a 
 shell which is usually calcareous, although in rare cases 
 it is composed of particles of sand united together. These 
 shells assume a great variety of forms, and many of them 
 are extremely beautiful. They are so exceedingly small 
 
PROTOZOA RHIZOPODA. 149 
 
 that " hundreds of them would hardly weigh a grain." 
 In some instances, the shell consists of only a single 
 chamber ; but usually there are a number of cells com- 
 municating with one another by minute openings. Some 
 of them are whorled like the shell of the nautilus, and, 
 on this account, were formerly believed to be minute 
 Mollusca. 
 
 The animal which secretes those beautiful shells from 
 the sea-water seems to be of even a lower organization 
 than the Amoeba, as it does not contain any nucleus or 
 contractile vesicle. It is very extraordinary that such a 
 lowly creature should be able to execute such a beautiful 
 piece of workmanship. We have here an illustration of 
 the fact, that " life is the cause of organization, and not 
 the consequence of it." 
 
 A foraminifer consists originally of a little mass of 
 jelly of a red or yellow colour. The outer coating of this 
 jelly secretes a shell consisting of a single chamber. As 
 the animal continues growing, it usually throws off buds, 
 each of which forms a fresh chamber. Thus, one of these 
 shells, minute as they are, generally contains a small 
 coloily of animals all united together into a living mass 
 by the canals which connect the chambers. In one of the 
 commonest groups (Globigerina), " when the process of 
 budding has produced a series of sixteen segments, the 
 next bud detaches itself, and begins to form a separate 
 shell." (Dr. Carpenter.) 
 
 The pseudopodia, instead of being blunt processes, as in 
 Amoeba, are long threads of inconceivable fineness. These 
 threads interlace one another, forming what has been 
 termed a sort of " animated spider's web." The interior 
 jelly is constantly sending out fresh threads in search of 
 particles of food, and receiving those which are drawn 
 back. Sometimes the pseudopodia are emitted through 
 the mouth of the shell, but more generally through minute 
 apertures (foramina) in the walls of the chambers. On 
 this account the name Foraminifera has been given to 
 the whole group. Strictly speaking, the pseudopodia are 
 
150 ZOOLOGY* 
 
 sent out from a film of jelly which surrounds the surface 
 of the shell. This, however, is in direct communication 
 with the sarcode in the interior. 
 
 These Foraminifera are extremely abundant, being, 
 
 Fia. 61. GROUP OF FORAMINIFERA. 
 
 probably, more numerous than all other animals together. 
 They are generally marine, and, in some countries, form 
 a large portion of the sand on the sea-shore. Along a 
 part of the west coast of Ireland, the whole sea-beach for 
 miles is mainly composed of their remains. They also 
 cover a wide area of the bottom of the North Atlantic. 
 They been have dredged up from a depth of three miles in 
 this ocean. A mass of these shells has the appearance of 
 white mud. Chalk, which forms in many countries an 
 
PROTOZOA RIIIZOPODA. 151 
 
 important portion of the earth's crust, is now known to 
 be almost wholly composed of a single species of Fora- 
 minifera (Globigerina). Several other limestones also 
 have been mainly formed by them. The earliest vestige 
 of animal life found in the rocks of the earth the eozoon 
 of the Lawrentian strata is a foraminifer. 
 
 The modern forms are all microscopic, but the extinct 
 nummulite (Lat. nummus, money ; Gr. lithos, a stone) 
 which has formed large masses of limestone, extending 
 from France to China, is sometimes three inches in cir- 
 cumference. The eozoon seems also, by continuous 
 budding, to have attained a large size. 
 
 217. (3.) The Radiolaria (Lat. radius, a ray) form the 
 third group of Rhizopoda. They are so called because 
 the pseudopodia surround the body like rays. They are 
 distinguished from the Foraminifera by having a siliceous 
 instead of a calcareous skeleton, which sometimes takes 
 the form of a shell ; and, in other cases, consists of loose 
 spicula (Lat. spiculum, a point), or needles. The best 
 known members of this group are the Polycystina (Gr. 
 2}olus } many; kustis, a bladder), which are even smaller 
 than the Foraminifera. They are furnished with minute 
 glassy shells, which, under the microscope, are objects of 
 extreme beauty. The animal consists of a little mass of 
 brown sarcode, which does not completely fill the shell. 
 The pseudopodia are protruded through apertures in the 
 shell, but they do not form a network. The white mud 
 dredged up from the bottom of the Atlantic contains a 
 considerable proportion of these shells, mixed with those 
 of the Foraminifera. They are also found very abun- 
 dantly as fossils in some tertiary rocks. 
 
 218. The Thalassicollida (Gr. thalassa, the sea ; kolla, 
 glue) are gelatinous animals found floating near the sur- 
 face of the ocean. They are sometimes an inch in 
 diameter. Their bodies are surrounded by radiating 
 pseudopodia, which sometimes form a network. The 
 skeleton consists of a series of flinty needles scattered 
 through the sarcode. 
 
152 ZOOLOGY. 
 
 219. The Acanthometra (Gr. acanthos, a thorn; 
 metra, the womb) have a skeleton of flinty spines which 
 radiate from the centre of the gelatinous body. Some of 
 the pseudopodia pass through canals in the interior of the 
 spines ; others proceed directly from the mass of sarcode. 
 They do not form a network. They are smaller than the 
 Thalassicollida, and are found floating at the surface of 
 the sea. 
 
 220. The Actinophrys, or sun-animalcule, is also re- 
 ferred by Dr. Carpenter to this group. 
 
 221. (4.) Spongida. Until recently, the sponges were 
 considered to be vegetables ; but they are now known to 
 be entitled to a place in the animal kingdom. What we 
 call a sponge is merely the framework or skeleton formed 
 by a mass of animals, each of which resembles an 
 Amoeba, and contains a nucleus. These skeletons are 
 generally horny, as in the sponge of commerce ; but 
 there are also calcareous and siliceous sponges. The 
 horny sponges are often strengthened by spicula, or 
 needles of siliceous or calcareous matter. These skeletons 
 are invested by a jelly-like mass, which resembles 
 in appearance the white of an egg. "When the sponge is 
 lifted out of the water, this jelly drains off. This gela- 
 tinous substance is permeated in every direction by canals 
 which communicate with the surface by a great number 
 of small openings, and a few large ones. Corresponding 
 openings may be observed in the fibrous skeleton. Cur- 
 rents of water enter by the smaller or inhalant aper- 
 tures; and, after passing through the system of canals, are 
 driven out through the larger or exhalant apertures. 
 Careful examination has shown that these currents are 
 produced by cilia, which are situated in spherical dila- 
 tations of the canals in the inner layer of the sponge. 
 These cavities are surrounded by particles of sarcode, 
 " each of which is furnished with a vibratile cilium." 
 The cilia all work so as to drive the water out by the 
 exhalant apertures. The currents thus produced bring 
 such particles of food as may be floating in the water, and 
 
PROTOZOA RHIZOPODA. 
 
 153 
 
 these are assimilated by the sponge particles in a similar 
 
 JL 
 
 FIG. 62. SPONGILLA. 
 
 A 1, 1 ', spicula ; 2, 2 /, gemmules ; 3, ciliated embryo. B, section of spon/jilla 
 the arrows indicate the direction of the currents; a, outer layer; b, inner layer; 
 c, ciliated chamber; <?, exhalant orifice. C, Mass of sponyilla the arrows in- 
 dicate the inhalant apertures; c c, openings leading to ciliated chambers; 
 single exhalant aperture hi the centre. 
 
154 ZOOLOGY. 
 
 manner to that by which the Amoeba is fed. " The 
 sponge represents a kind of subaqueous city, where the 
 people are arranged about the streets and roads in such 
 a manner that each can easily appropiiate his food from 
 the water as it passes along." (Huxley.) 
 
 222. Reproduction in the sponges is effected in two 
 different ways. In the fresh-water sponge (spongilla), 
 towards the approach of winter, extremely minute 
 bodies called seeds, or gemmules, are formed in 
 the inner layer. One of these gemmules consists of a 
 number of sponge particles, coated over with a cyst. This 
 cyst has imbedded in it spicula of a very curious form, 
 consisting of an axle with a toothed wheel at each end. 
 During the winter the spongilla dies ; and, on the arrival 
 of spring, the sponge particles pass out through an open- 
 ing in the cyst, and become sponges like the original. 
 
 During the summer months some of the sponge par- 
 ticles are changed into ova, others into sperm cells. 
 The resulting embryos are provided with cilia. After 
 swimming about for a time they lose their cilia, attach 
 themselves to some solid object, and are developed into 
 sponges. 
 
 223. Distribution. Sponges are found both in salt 
 and fresh water, and are met with in most parts of the 
 world. The sponges of commerce are all marine, and are 
 confined to the warmer regions. The best sponges are 
 obtained from the Greek islands, a coarser kind being 
 procured from the Bahamas. Fossil sponges are common 
 in various geological formations, but are especially 
 abundant in the chalk. The flint nodules which abound 
 in this formation are believed to have been mainly formed 
 by them. It is an interesting and suggestive fact that 
 siliceous sponges, similar to those found in the chalk, have 
 been recently dredged from the bottom of the Atlantic, 
 along with the shells of the Foraminifera. 
 
PROTOZOA GREGARIXIDA. 155 
 
 CLASS 3. Gregarinida. 
 
 224. The Gregarinida (Lat. grex, a flock) are internal 
 parasites, infesting the alimentary canal of the cockroach, 
 the earthworm, and other animals. They are destitute of 
 a mouth, and do not protrude pseudopodia. Like other 
 internal parasites, they subsist by imbibing the juices of 
 the animals in which they live. They have the appearance 
 of minute worms, and are sometimes about half an inch 
 long, though generally much smaller. The outer coating 
 is membranous, the interior being filled with sarcode. 
 At one point in the central jelly there is a vesicle, or 
 nucleus, enclosing a solid particle or nucleolus. These 
 are probably reproductive organs. 
 
 225. In certain cases these animals become changed 
 into minute balls, enclosed by a cyst. The nucleus and 
 nucleolus then disappear, and the sarcode is formed into 
 little masses, which are at first round, but afterwards 
 lengthen out, and become pointed at each end. These are 
 called Pseudo-Navicellae (Navicella being a microscopic 
 plant or diatom). The cyst afterwards bursts, and the 
 Pseudo-Navicellze pass out of the body of the animal in 
 which the Gregarinse reside. Some of these are taken 
 into the body of another animal an earthworm, for 
 example ; and then the little mass of sarcode, inclosed 
 within the shell of the Pseudo-Navicella, is set free, and 
 begins to thrust out processes after the manner of an 
 Amoeba. Ultimately, this little animal is developed into 
 a Gregarina like that from which it proceeded. 
 
156 ZOOLOGY. 
 
 QUESTIONS V. 
 
 1. Give the derivation of the term Actinozoa. 
 
 2. Give examples of this class. 
 
 3. What are its principal characteristics ? 
 
 4. Explain the terms MESENTERIES, ECTODERM, ENDODERM, 
 
 CCENOSARC, ACTINOSOMA. 
 
 5. Give an account of the structure of the SEA- ANEMONE. 
 
 6. What is coral ? 
 
 7. What is the distinction between SCLERODERMIC and SCLERO- 
 
 BASIC corals ? 
 
 8. Give an account of the various forms of CORAL REEFS. 
 
 9. What is an ATOLL ? 
 
 10. How does the red coral of the Mediterranean differ from the 
 
 reef -building corals ? 
 
 11. Describe the Ctenopliora? 
 
 12. Define the class Hydrozoa? 
 
 13. Give examples of this class. 
 
 14. How does the section of a Hydrozob'n differ from that of an 
 
 Actinozoon ? 
 
 15. Distinguish between POLYPES, POLYPITES, and POLYPIDES. 
 
 16. What is the hydrosoma ? 
 
 17. What are the leading distinctions between the Hydrozoa and 
 
 the Polyzoa ? 
 
 18. Give an account of the structure and habits of the FRESH- 
 
 WATER HYDRA. 
 
 19. What are THREAD- CELLS ? 
 
 20. Give an account of the reproduction of the Hydra. 
 
 21. Describe the CORYNID^E or CLUB-HYDRAS. 
 
 22. What is meant by ALIMENTARY ZOOIDS ? 
 
 23. What are GONOPHORES ? 
 
 24. Give an account of the different kinds. 
 
 25. What is the MANUBRIUM ? 
 
 26. Give an account of the development of the NAKED-EYED 
 
 MEDUSAE. 
 
 27. What is meant by "alternation of generations ? " 
 
 28. Describe the Sertularidce. 
 
 29. How do they differ from the Corynidce ? 
 
 30. Give an account of the Lucernaridce. 
 
 31. What is a HYDRA-TUBE? 
 
 32. Give an account of the development of the great JELLY-FISHES. 
 
 33. What are the principal points of difference between tho 
 
 HIDDEN-EYED and NAKED-EYED MEDUSAE? 
 
 34. Why are the Infusoria so called ? 
 
 35. Define this class. 
 
 36. Give examples. 
 
QUESTIONS. 157 
 
 37. Describe Paramoeciuni. 
 
 38. Explain the terms CORTICAL LAYER, CONTRACTILE VESICLE, 
 
 NUCLEUS, NUCLEOLUS. 
 
 39. What various modes of reproduction have been observed in 
 
 this class ? 
 
 40. Describe VerticeUa, and give an account of the various modes 
 
 of reproduction observed in tins group. 
 
 41. Define the Rhizopoda. 
 
 42. Give examples. 
 
 43. What are PSEUDOPODIA ? 
 
 44. What is the mode of reproduction in the Amoeba ? Give a 
 
 description of this animal. 
 
 45. What is the origin of the term Foraminlfera ? 
 
 46. How do they differ from Amoeba ? 
 
 47. Where are they usually found ? 
 
 48. Describe the shells secreted by these animals. 
 
 49. How do the Radiolaria differ from the Foraminlfera ? 
 
 50. What are the Polyclstlnos ? 
 
 51. Describe the Thalasslcolllda. 
 
 52. Give an account of the Acanthometra. 
 
 53. What is the structure of a sponge ? 
 
 54. What is the nature of the frame-work or skeleton ? 
 
 55. What are the INHALANT and EXHALANT apertures ? 
 
 56. How is a sponge fed ? 
 
 57. Describe the mode of reproduction in the fresh- water sponge. 
 
 58. What are SPICULA ? What are GEMMULES ? 
 
 59. AVhat are the Gregarinidce ? 
 
 60. What is their usual habitat ? 
 
 61. Wliat are PSEUDO-NAVICELL^E ? 
 
GLOSSARY 
 
 ^ Abdomen (Lat. dido, I conceal) In Mammalia, that part of the 
 
 body cavity Which is separated from the thorax or chest by 
 
 the diaphragm. 
 Acalepha (Gr. akakplie, a nettle) Jelly fishes or sea-nettles, so 
 
 called on account of their ability to sting by means of 
 
 "thread cells." 
 Acanthocephala (Gr. acanthos, a thorn ; kepliale, the head) A 
 
 group of internal parasites, so called because the head is 
 
 armed with spines. 
 Acephalous (Gr. a, without ; kepJiak, the head) Without a 
 
 distinct head. The Lamellibranchiata are sometimes called 
 
 Acephala. ' 
 Actinosoma (Gr aktis, a ray ; soma, body) A term applied to 
 
 the whole body of an actinozoon, whether simple or com- 
 pound. 
 Actinozoa (Gr. dktis, a ray ; zoon, an animal) A class of 
 
 ccelenterata. 
 Albumen (Lat. albus, white) A substance resembling the white 
 
 of an egg. 
 Alimentary Canal (Lat. alo, I nourish) The tube through which 
 
 the food passes. 
 ^ Allantois (Gr. alias, a sausage) A foetal membrane in mammals, 
 
 birds, and reptiles. 
 Ambulacra (Lat. ambulacrum, a garden walk) The spaces in the 
 
 tests of sea-urchins and star-fishes, containing the apertures 
 
 through which the "tube feet" are protruded. 
 Ametabolic (Gr. a, without; metabole, change) A term applied to 
 
 those insects which do not undergo metamorphosis. 
 Ammonites (so called from their resemblance to the horns on the 
 
 statues of Jupiter- Ammon) A group of extinct chambered 
 
 shells belonging to the class Cephalopoda. 
 t^Amnion (Gr. amnos, a lamb) A fcetal membrane in mammals, 
 
 birds, and reptiles. 
 Amoeba (Gr. amoibe, a change) One of the Rldzopoda, which 
 
 constantly changes its shape. 
 ^Amphibia (Gr. amphi, both ; bios, life) A class of Vertebrata 
 
 adapted for breathing in water when young, and in air when 
 
 mature. The terin was formerly applied to aquatic mammals, 
 
 such as the seals, 
 
160 ZOOLOGY. 
 
 V Amphiccelus (Gr. amphi, both ; koilos, hollow) A term applied to 
 
 double-concave vertebral. 
 u Amphioxus (Gr. amphi, both ; oxus, sharp) A little fish (the 
 
 lancelet) which tapers at both ends. 
 Anarthropoda (Gr. a, without ; arthros, a joint ; pous, a foot) A 
 
 division of Annulosa, so called because they are destitute of 
 
 jointed limbs. 
 I Anchylosis (Gr. ankulos, crooked) The union of two bones which 
 
 are immovably united together. 
 
 Animalcule (diminutive of animal) The popular name for a micro- 
 scopic animal. 
 
 Annelida (Lat. annulos, a ring) A class of Anarthropoda, em- 
 bracing the earth-worm and the leech, &c. 
 Annuloida (Lat. annulus, a ring) A sub-kingdom, including the 
 
 Eclunodermata and Scolecida. 
 Annulosa (Lat. annulus, a ring) A sub-kingdom, composed of the 
 
 Arthropoda and Anarthropoda. Formerly called Articulata. 
 Antenna (Lat. antenna, the yard of a ship) The jointed 
 
 appendages of the head in Insecta, Crustacea, and Myria- 
 
 poda. 
 Antennules (diminutive of antennae) The shorter pair of an- 
 
 tennse in the Crustacea. 
 
 Arachnida (Gr. arachne, a spider) A class of Artltropoda, in- 
 cluding spiders, scorpions, and mites. 
 Archseopteryx (Gr. archaios, ancient ; pleryx, a wing) An extinct 
 
 bird found in the oolitic rocks; the only representative of 
 
 the order Saururce of Huxley. 
 Ascidioida (Gr. askos, a bag) A class of Molluscoida, so called 
 
 because they resemble in shape a two-necked bottle. This 
 
 class is also termed Tunlcata. 
 iXktlas (Gr. Atlas, the god that holds up the earth) The vertebra 
 
 which supports the skull, 
 tx Atrium (a hall) Applied to the cavity in the Tunlcata into 
 
 which the intestine opens. 
 (/ Auricle (diminutive of auris, an ear) One of the cavities of the 
 
 heart which receives blood, and transmits it to the ventricle. 
 j/Autophagi (Gr. autos, self; phago, I eat) A term applied to 
 
 those birds which are able to run about, and obtain food as 
 
 soon as they leave the shell. 
 
 Aves (Lat. avis, a bird) One of the classes of Vertebra-la. 
 Avicularium (Lat. avlcida, a little bird) An appendage of the 
 
 Polyzoa, resembling the head of a bird. 
 
 Belemnites (Gr. belemnos, a dart) An extinct group of Cephalo- 
 poda, allied to the cuttle-fishes. 
 
 Bilateral (Lat. bis, twice; latus, a side) Having two similar 
 sides. 
 
GLOSSARY. 1G1 
 
 Bivalve (Lat. Iris, twice; valvce, folding doors) Applied to the 
 shells of the Lamellibranchiata and Bracltiopoda, which are 
 composed of two pieces. 
 
 Brachiopoda (Gr. brachion, an arm; pous, a foot) A class of 
 
 Molluscoida, having long ciliated arms, and bivalve shells. 
 i/Branchiae (Gr. branchice, gills) The breathing organs of fish and 
 other aquatic animals. 
 
 Branchiogasteropoda (Gr. branchke, gills ; gaster, the belly ; pous, a 
 foot) A group of Gasteropoda that breathe by means of grills. 
 ^ Bronchi (Gr. bronchos, the windpipe) The branches of the wind- 
 pipe that permeate the lungs. 
 
 Bryozoa (Gr. bruon, moss; zoon, an animal) Another name for 
 the Polyzoa. 
 
 Byssus (Gr. bussos, flax) Silky threads by which the mussel and 
 other lamettibranchs attach themselves to rocks. 
 
 Caeca Blind processes in the alimentary canal. 
 ^Canine Teeth (Lat. canis, a dog) The eye teeth, so called because 
 they are. well developed in the dog and other carnivorous 
 animals. 
 Carapace The upper shell of crabs and lobsters ; the upper half 
 
 of the case in which tortoises and turtles are enclosed. 
 ^-Carpus (Gr. carpos, the wrist) The bones that are placed be- 
 tween the fore-arm and the hand. 
 ^-Caudal (Lat. cauda, the tail) Belonging to the tail. 
 Cephalopoda (Gr. Jcephale, the head ; pous, foot) A class of Mol- 
 lusca, to which the cuttle-fish and nautilus belong. They 
 are so called because the organs of locomotion are arranged 
 round the head. 
 
 Cephalothorax (Gr. kephak, the head; thorax, breast) That part 
 of the body in Crustacea and Arachnida which is formed 
 by the tmion of the head and thorax. 
 fc Cervical (Lat. cervix, the neck) Belonging to the neck. 
 Chsetognatha (Gr. chaite, hair; ynathos, a jaw) A class of Anar- 
 
 thropoda, containing the Sagitta only. 
 Chitine (Gr. chiton, a coat) The horny substance which forms 
 
 the exoskeleton of insects, &c. 
 Chrysalis (Gr. chrusos, gold) The pupa state of an insect, so 
 
 called because it is sometimes of a golden colour. 
 V- Chyle (Gr. chulos, juice) The milky fluid which results from the 
 
 digestion of food. 
 ^ Chyme (Gr. chumos, juice) The pulpy mass into which food is 
 
 formed by the action of the gastric juice. 
 
 i Cilia (Lat. cilium, an eye-lash) Microscopic hair-like organs 
 which, by their movements, produce currents in the water, 
 and thus supply the Infusoria and other animals with minute 
 particles of food. They also serve as means of locomotion. 
 
 ' 15 E, I, 
 
162 ZOOLOGY. 
 
 v Cirri (Lat. cirrus, a curl of hair) A term applied to the feet of 
 barnacles and acorn-shells, from their resemblance to ten- 
 drils. The filaments attached to the arms of the Brachio- 
 poda. 
 
 Cirripedia (Lat. cirrus, a curl; pes, a foot) A division of Crus- 
 tacea, including the barnacles and acorn-shells. They are so 
 called on account of their curled feet. 
 
 Clavicle (Lat. clavicula, a little key) The collar-bone of the Ver- 
 tebrata. 
 
 Cloaca (Lat. a sewer) The cavity into which the intestine, uri- 
 nary, and genital organs open in birds, reptiles, and one 
 order of mammals (Monotremata). An analogous cavity is 
 found in some invertebrate animals. 
 
 Cocoon (Fr. cocon) The covering of an insect in the pupa state, 
 sometimes consisting of silky hairs. 
 
 Ccelenterata (Gr. koilos, hollow; enteron, an intestine) The sub- 
 kingdom which includes the Hydrozoa and Actinozoa. They 
 are distinguished from the Protozoa, mainly, in having a 
 hollow digestive cavity. 
 
 Ccenosarc (Gr. Jcoinos, common; sarx, flesh) The common con- 
 necting stem in the compound Hydrozoa. 
 
 Commissures (Lat. committo, I join together) The nerve filaments 
 which unite the ganglia or nerve-centres. 
 
 Conchifera (Lat. concha, a shell; fero, I bear) A name sometimes 
 
 applied to the Lamellibrancldata. 
 
 VCondyle (Gr. Jcondulos, a knuckle) The articulating surface of a 
 bone, especially applied to the articulating surface or sur- 
 faces of the occipital bone, which join the skull to the atlas, 
 or first joint of the vertebral column. 
 
 Coracoid (Gr. korax, a crow) A second clavicle found in birds, 
 reptiles, and Monotremata. In man, the "coracoid process" 
 of the scapula resembles the beak of a crow. 
 
 Corallum (Lat. for coral) The calcareous structure secreted by 
 the tissues of the Actinozoa, generally called " coral." 
 
 Coriaceous (Lat. corium, a hide) Resembling leather. 
 : Corpus Call osum (Lat. "firm body") The band of nerve-fibres 
 which unites the two hemispheres of the cerebrum in Mam- 
 malia. 
 
 Corpuscles (Lat. corpusculum, a little body) The rounded solid 
 particles found floating in blood. In most mammals they 
 have the form of " biconcave discs." 
 
 Cortical Layer (Lat. cortex, bark) In the Infusoria this term is 
 applied to the middle layer of the body. It lines the cuticle, 
 and surrounds the central mass of sarcode. 
 l^Cranium (Gr. kranion, the skull) The bony or cartilaginous case 
 
 which surrounds the brain. 
 \X/rop An expansion of the oesophagus found in birds,. 
 
GLOSSARY. 163 
 
 Crustacea (Lat. crusta, a crust) A class of Annulosa, including 
 crabs, lobsters, &c. They are so called because they are 
 covered with a shell or hard crust. 
 
 Ctenoid (Gr. kteis, a comb; eidos, form) A term applied to the 
 scales of fishes which have comb-like margins. 
 
 Ctenophora (Gr. kteis, a comb; phero, I bear) A group of Actino- 
 zoa, whose swimming organs consist of comb-like bands of cilia. 
 
 Cursores (Lat. curro, I run) An order of birds, including the 
 ostrich, emeu, cassowary, and rhea, which are destitute of 
 the power of flight, 
 i Cuticle (Lat. cutis, the skin) The outer layer of the skin. 
 
 Cycloid (Gr. kuklos, a circle; eidos, form) A term applied to cir- 
 cular fish scales. 
 
 Cyst (Gr. kustis, a bladder) A bladder-like sac. 
 
 Dermal (Gr. derma, skin) Belonging to the skin. 
 Diaphragm (Gr. diaphragma, a partition) The muscle which 
 
 separates the thorax from the abdomen in the Mammalia. 
 Diatomaceae (Gr. diatemno, I cut asunder) A group of microscopic 
 
 plants, provided with siliceous coverings. 
 Dibranchiata (Gr. dis, twice ; branchiae, gills) The cuttle-fish 
 
 tribe, so called because they possess two gills. 
 t Didelphia (dis, twice ; delphus, the womb) The marsupial 
 
 mammals. 
 
 Digit (Lat. digitus, a finger) A finger or toe. 
 Dorsal (Lat. dorsum, the back) Belonging to the back. 
 
 Echinodermata (Gr. echinos, a hedgehog; derma, skin) A class of 
 animals, including the sea-urchins and star-fishes. It is so 
 called on account of the spines with which the integument 
 is generally furnished. 
 
 . Ectocyst (Gr. ektos, without; kustis, a bladder) The outer cover- 
 ing of the Poly zoa. 
 
 Ectosarc (Gr. ektos, without; sarx, flesh) The outer layer of 
 sarcode in the Amoeba. 
 
 Elytra (Gr. elytron, a sheath) The horny front pair of wings in 
 beetles, which form a case for the protection of the mem- 
 branous pair. 
 
 Embryo (Gr. en, in ; bruo, I swell) The earliest stage in which 
 an animal may be discerned in the egg. 
 
 Encrinite (Gr. kryion, a lily) The "stone lily,'* a group of 
 Echinodermata. 
 
 Encystment (Gr. kustis, a bladder) A change undergone by some 
 of the Protozoa, in which they become motionless, and cover 
 themselves with a " cyst" or sac. 
 
 Endocyst (Gr. endon, within; kustis) The inner layer of the 
 Polyzoa. 
 
164 ZOOLOGY. 
 
 Endoderm (Gr. endon; derma, skin) The inner layer of the 
 
 Coelenterata. 
 Endosarc (Gr. endon; sarx, flesh) The inner sarcode of the 
 
 Amoeba. 
 Entomostraca (Gr. entoma, insects; ostrakon, a shell) A group of 
 
 minute fresh- water Crustacea. 
 
 Entozoa (Gr. entos, within ; zoon, an animal) Intestinal worms. 
 ^Epidermis (Gr. epi, upon ; derma, the skin) The cuticle or outer 
 
 layer of the skin. 
 Equilateral (Lat. cequus, equal; latus, a side) Equal-sided; applied 
 
 to the shells of the Bracliiopoda. 
 Equivalve Having equal valves, as in most of the shells of the 
 
 Lamellibranchiata. 
 Exoskeleton (Gr. exo, without) The outer skeleton of insects, &c., 
 
 formed by a hardening of the integument. 
 
 Fauna (Lat. fauni, rural gods) The native animals of a country 
 
 or district. 
 
 ! Femur The thigh bone, placed between the pelvis and the tibia in 
 the higher Vertebrates. 
 
 Fibula (Lat. a brooch) The smaller bone of the leg, correspond- 
 ing to the ulna of the fore-arm. 
 
 Fission (Lat. findo, I cleave) A method of reproduction by self- 
 division, found in the Infusoria and other animals. 
 
 Flora (Lat. the goddess of flowers) The plants of a country or 
 district. 
 
 Foot- Jaws Certain limbs of the Crustacea which serve as masticat- 
 ing organs. 
 
 Foot-Tubercles The unjointed limbs of the Annelida. 
 
 Foraminifera (Lat. foramen, a hole ; fero, I bear) A group of 
 Rhizopoda which possess minute, calcareous shells. These 
 shells are perforated by minute apertures, through which 
 pseudopodia are protruded. 
 
 . Furculum (Lat. furca, a fork) The V-shaped bone in birds, 
 formed by the union of the clavicles. It is commonly called 
 the * ' merry- thought. " 
 
 Ganglion (Gr. a knot) A mass or centre of nervous matter, con- 
 taining nerve cells, from which nerve fibres proceed. 
 ^Ganoid (Gr. ganos, splendour) A term applied to fish scales, 
 which are composed of an inner layer of bone, and an outer 
 layer of shining enamel. 
 
 Gasteropoda (Gr. gaster, the belly; pous, foot) A class of Mollusca 
 usually furnished with univalve shells. They are so called 
 because the locomotive organ consists of a broad muscular 
 disc, occupying the lower surface of the body. 
 
GLOSSARY. 165 
 
 Gemmation (Lat. gemma, a bud) A method of reproduction by 
 
 which new individuals are formed from buds which arise on 
 
 the body of the parent. 
 Gemmule (Lat. a little bud) A minute mass of spongy particles 
 
 covered with a cyst. 
 Gizzard A part of the stomach of birds, insects, &c., furnished 
 
 with muscular walls. 
 Globigerina (Lat. globus, a ball; gcro, I carry) A group of Fora- 
 
 mini/era, found abundantly in chalk. 
 Graptolites (Gr. grapho, I write ; lithos, a stone) An extinct 
 
 group of ffydrfiioa, whose remains are found in the Silurian 
 
 strata. 
 
 Gregarinida (Lat. grex, a flock) A class of Protozoa. 
 Guard The fibrous sheath which protects the phragmacone of 
 
 the Belemnite. 
 
 i- Haemal (Gr. haima, blood) Belonging to the blood. 
 
 Hectocotylus (Gr. hekaton, a hundred; kotulos, a cap) One of the 
 arms of the male cuttle-fishes modified into a reproductive 
 organ. 
 
 Hemimetabolic (Gr. hemi, half ; meldbole, change) Insects which 
 undergo incomplete metamorphosis. 
 
 Hermaphrodite (Gr. Hermes, Mercury; Aphrodite, Venus) Having 
 
 the sexes combined in the same individual. 
 
 i^ileterocercal (Gr. heteros, different; kerkos, a tail) Applied to 
 the caudal or tail fin of fishes when the two lobes are 
 unequal. 
 
 Heterophagi (Gr. heteros, different; phago, I eat) A term applied 
 to birds which come from the egg in a helpless state, requir- 
 ing to be fed for a time by the parents. 
 
 Holometabolic (Gr. holos, whole; metabole, change) A term ap- 
 plied to insects whose metamorphosis is complete. 
 
 Holostomata (Gr. holos, whole; stoma, mouth) A group of Gastero- 
 poda, in which the aperture of the shell is not furnished 
 with a notch or canal. 
 ^Homocercal (Gr. homos, like; kerfcos, tail) A term applied to the 
 
 tail fins of fishes which are divided into two equal lobes. 
 . Humerus The bone which connects the radius with the pectoral 
 arch in vertebrates. 
 
 Hydrosoma (Gr. hudra, a water dragon; soma, body) The entire 
 body of a hydrozoon, whether simple or compound. 
 
 HydrothecsB (Gr. hudra; theka, a case) The horny cups inhabited 
 by the sertularian polypites. 
 
 Hydrozoa (Gr. hudra; zoon, an animal) A class of Codmterata, 
 
 exemplified by the fresh-water hydra and jelly-fishes. 
 UHyoid The tongue bone, so called because in man it is shaped 
 like the letter U. 
 
166 ZOOLOGY. 
 
 Ichthyopsida (Gr. ichthus, a fish; opsis, appearance) The division 
 
 of the Vertebrata which includes the Amphibia and fishes. 
 Ichthyosaurus (Gr. ichthus; saurus, a lizard) An extinct reptile 
 
 found in the secondary rocks. 
 
 Imago (Lat. an image) The perfect form of insects, 
 t^ Incisors (Lat. incido, I cut) The front or cutting teeth of 
 
 mammals. 
 Incubation (Lat. incubo, I sit) The act of sitting on eggs, in order 
 
 to develop the contained embryos. 
 Inequilateral (Lat. in, not; cequus, equal; latus, a side) Applied 
 
 to the shells of the Lamellibranchiata, which have the two 
 
 sides unequal. 
 
 Inequivalve Having two unequal valves. 
 Infusoria (Lat. in, on ; /undo, I pour) A class of Protozoa, so 
 
 called because they abound in infusions of animal or vegetable 
 
 substances. 
 
 Insecta (Lat. inseco, I cut into) A class of Arthropoda. 
 Invertebrata (Lat. in, not ; vertebra, a joint of the backbone) 
 
 Animals which are destitute of a skull and spinal column. 
 
 Labium (Lat. lip) The lower lip in the Arthropoda. 
 Labrum (Lat. lip) The upper lip in the Arthropoda. 
 ^^Labyrinthodon (Gr. labyrinthos, a maze; odous, tooth) An extinct 
 
 amphibian, so called from the structure of its teeth. 
 Lamellibranchiata (Lat. lamella, a plate ; Gr. branchia, a gill) A 
 
 class of Molhisca, so called because their gills are composed 
 
 of folds of membrane. 
 Larva (Lat. a mask) The first stage of an insect after it comes 
 
 from the egg. It is commonly called a caterpillar. 
 Lens (Lat. a bean) A term applied to the hexagonal facets into 
 
 which the eyes of insects are divided. 
 Lobes Various rounded portions of animals are so called. 
 Lucernarida (Lat. lucerna, a lamp) A group of Hydrozoa. 
 \JLumbar (Lat. lumbus, the loin) Belonging to the loins. 
 
 Madreporiform Applied to the tubercle by which the anibulacral 
 
 system of the sea-urchins communicates with the exterior. 
 
 It is so called because it is perforated with small holes like 
 
 madrepore coral. 
 Mammalia (Lat. mamma, the breast) The class of Vertebrata 
 
 which suckle their young. 
 Mandible (Lat. mando, I chew) The lower jaw in the Vertebrata; 
 
 in Arthropoda, the upper pair of jaws ; the beak of the 
 
 Cephalopoda. 
 
 Mantle The outer covering of the Mollusca. 
 Manubrium (Lat. a handle) The handle-shaped polypite which is 
 
 suspended from the centre of the disc in the Medusa* 
 
GLOSSARY. 167 
 
 ^ Marsupialia (Lat. marsiipium, a pouch) An order of Mammalia 
 in which the immature young are protected in a pouch, 
 placed beneath the abdomen of the female. 
 1-- Masticatory (Lat. mastico, I chew) A term applied to organs 
 
 used in chewing food. 
 
 > Maxilla (Lat. jaws) The lower pair, or pairs, of jaws in the 
 Artliropoda. 
 
 Maxillipedes (Lat. tnaxillce, jaws; j)es, a foot) Or "foot jaws," 
 the modified limbs of the Crustacea, which are used as 
 masticatory organs* 
 
 Medusae The sea-nettles or jelly-fishes, so called because their 
 tentacles resemble the hair of the Medusa, or chief of the 
 gorgons, which was said to consist of snakes. 
 
 Mesenteries (Gr. mesos, the middle; enter on, an intestine) The 
 vertical partitions which divide into chambers the interven- 
 ing space between the alimentary tube and the body wall of 
 a sea-anemone. 
 
 '., Metacirpus (Gr. meta, after; carpus, the wrist) The bones which 
 intervene between the wrist and the fingers in the higher 
 vertebrates. 
 
 MetaUrsus (Gr. meta; tarsos, the hollow part of the foot) The 
 tones which intervene between the tarsus or ankle bones 
 and the phalanges of the toes. 
 
 I Molars (Lat. mola, a mill) The teeth which are not preceded by 
 a milk set the " grinders." 
 
 Mollusca (Lat. mollis, soft) One of the sub-kingdoms, so 
 called from the soft nature of their bodies. It includes 
 the classes Cephalopoda, Gasteropoda, Pteropoda, and 
 Lamellibranchiata. 
 
 Molluscoida (Lat. mollis, soft; Gr. eldos, form) A sub-kingdom, 
 including the Brachiopoda, Asddioida, and Polyzoa. 
 
 Monad (Gr. monas, a unit) An exceedingly minute infusorian. 
 
 Monodelphia (Gr. monos, single; delphus, womb) A division of 
 
 Mammalia, including all the higher members of the group. 
 fc> Monotremata (Gr. monos, single; trema, an opening) An order of 
 Mammalia, in which the intestine and the ducts of the uri- 
 nary and genital organs open into a common cloaca. It 
 includes the duck mole and the porcupine ant-eater. 
 
 Multivalve (Lat. multus, many ; valvce, folding doors) A term 
 applied to certain gasteropod shells which are composed of 
 several pieces. 
 
 Myriapoda (Gr. murios, ten thousand ; pous, a foot) A class of 
 Artliropoda, distinguished by having numerous feet. It in- 
 cludes the centipedes and millipedes. 
 
 Nectocalyx (Gr. necho, I swim; fcahix, a cup) The swimming bell 
 of a jelly-fish. 
 
168 ZOOLOGY. 
 
 Nematoidea (Gr. nema, thread; eidos, form) A group of Scokcida, 
 
 including the "thread worms" and the "round worms." 
 V Neural (Gr. neuron, a nerve) Belonging to the nervous system. 
 
 Nucleated Possessing a nucleus or central solid particle. 
 Nucleolus A minute particle attached to the " nucleus," or sup- 
 posed ovary of the Infusoria. 
 
 Occipital Belonging to the occiput, or that part of the skull which 
 
 forms the back portion of the head. 
 Ocelli (Lat. diminutive of ocuhis, eye) The simple eyes of 
 
 spiders, crustaceans, molluscs, and some insects. 
 Octopoda (Gr. octo, eight ; pous, foot) A group of cuttle-fishes, 
 
 possessing eight arms. 
 Odontophore (Gr. odous, tooth; phero, I fear) The lingual ribbon, 
 
 or tooth-bearer, of the higher Mollusca. 
 (Esophagus (Gr. olsos, a reed; phago, I eat) The tube leading 
 
 from the mouth to the stomach.. 
 tOperculum (Lat. a lid) The bony flap which covers the gills of 
 
 fishes ; the horny disc which closes the shells of the Gastero- 
 poda. 
 M)rnithodelphia (Gr. ornis, a bird; delphus, womb) The lowest 
 
 division of the Mammalia, including the Monotremata. 
 Oscula (Lat. diminutive of os t mouth) The large or exhalant 
 
 apertures of sponges. 
 Otoliths (Gr. 'ous, ear; lithos, stone) Concretions found in the 
 
 auditory sacs of fishes, Crustacea, and Mollusca. 
 tXJvoviviparous (Lat. ovum, egg; vivo, I live; pario, I bring forth) 
 
 A term applied to those animals which retain the eggs 
 
 within their bodies until they are hatched. 
 
 Pallium (Lat. a cloak)The "mantle" of the Mollusca; "pallial 
 line," the impression left in the shell by the muscular margin 
 of the mantle. 
 
 Palpi (Lat. palpo, I touch) Organs of touch connected with the 
 appendages of the mouth in the Arthropoda. 
 
 Parietal (Lat. paries, a wall) Belonging to the walls of the body. 
 
 Parieto-splanchnic (Lat. paries; Gr. splanclma, the internal organs) 
 A ganglion in the higher Mollusca, which sends nerve- 
 fibres to the mantle, gills, and internal organs. 
 
 Pectoral (Lat. pectus, the chest) Belonging to the chest. 
 
 Pedal (Lat. pes, foot) Belonging to the foot, in Mollusca. 
 
 Pedicellarise (Lat. pedicdlus, a louse) Curious appendages at- 
 tached to the sea-urchins. 
 
 Peduncle (Lat. pedunculus, a stalk) The muscular stalk by which 
 the Brachiopoda are attached; the stem by which the bar- 
 nacle connects itself with wood or other objects. 
 
GLOSSARY. 169 
 
 ^P elvis The bony arch to which the hind limbs of the Vertebrate 
 
 are attached. 
 Pericardium (Gr. peri, around; kardia, the heart) The membrane 
 
 that surrounds the heart. 
 
 Perigastric (Gr. peri; gaster, the stomach) The space which sur- 
 rounds the stomach and other internal organs. 
 Perivisceral (Gr. peri; Lat. viscera, the internal organs) The 
 
 space surrounding the viscera. 
 Phalanges (Gr. phalanx, a row) The bones which compose the 
 
 digits of the higher Verlebrata. 
 - Pharynx The upper part of the gullet. 
 Phragmacone (Gr. pliragma, a partition; konos, a cone) That 
 
 part of the internal shell of a belemnite which is divided 
 
 into chambers by partitions. 
 Pisces (Lat. piscis, a fish) A class of Vertebrata. 
 Placenta (Lat. a cake) An organ containing a network of blood- 
 vessels, by which the young of the higher mammals receive 
 
 nourishment from the mother before birth. 
 Place-id (Gr. plax, a plate ; eidos, form) Applied to the scales of 
 
 sharks and rays, which are in the form of irregular bony 
 
 plates, sometimes armed with spines. 
 Planarida (Gr. plane, wandering) A group of Turbellaria. 
 Pleura (Gr. the side) The membrane which surrounds the lungs 
 
 of the higher Vertebrata. 
 Pneumatic (Gr. pneuma, air) Containing air. 
 Polycystina (Gr. polus, many ; kustis, a bladder) A group of 
 
 Protozoa with minute perforated siliceous shells. 
 Polygastrica (Gr. polus ; gaster, stomach) The name given by 
 
 Ehrenberg to the Infusoria. 
 
 Polypary The chitinous covering of the compound Hydrozoa. 
 Polype (Gr. polus, many ; pous, foot) A single individual in the 
 
 Actinozoa. 
 
 Polypide One of the zooids in the Polyzoa. 
 Polypite One of the zooids in the Hydrozoa. 
 Polyzoa (Gr. polus, many ; zb'on, an animal) A class of Mollus- 
 
 coida called also Bryozoa. 
 Polyzoarium The polypidum, or chitinous covering of the 
 
 Hydrozoa. 
 Prsemolars The permanent molars which succeed the molars of 
 
 the milk set of teeth ; the bicuspid teeth, 
 t^roccelus (Gr. pro, front; koilos, hollow) Applied to vertebrae 
 
 which are hollow in front. 
 Protoplasm (Gr. protos, first ; plasso, I mould) The primitive 
 
 basis of all organic tissues, sometimes used as a synonym for 
 
 sarcode. 
 
 Protozoa (Gr. protos; zoon, an animal) The lowest of the sub- 
 kingdoms. 
 
170 ZOOLOGY. 
 
 Pseudo-haemal (Gr. pseudos, false; liaima, blood) Applied to the 
 circulatory system of the Annelida. 
 
 Pseudo-hearts Contractile cavities found in the Brachiopoda, 
 formerly believed to be hearts. 
 
 Pseudo-Navicellse (Gr. pseudos; Navicula, a diatom) The unde- 
 veloped form of the Gregarinida. 
 
 Pseudo-podia (Gr. pseudos; pous, foot) Processes thrust out by 
 the Rhizopoda from the surface of their bodies, which serve 
 the purpose of limbs. 
 
 Pteropoda (Gr. pteron, wing ; pous, foot) A class of Mollusca which 
 swim by means of wing-like processes attached to the head. 
 
 Pulmo-Gasteropoda A group of Gasteropods which breathe by 
 pulmonary sacs or lungs. 
 
 Pupa (Lat. a doll) The stage of metamorphosis of an insect in- 
 termediate between the larva and imago. It is also called a 
 chrysalis. 
 
 Radiata (Lat. radius, a ray) One of the sub-kingdoms of Cuvier. 
 This group is now broken up, its members being assigned 
 to several sub-kingdoms (Ccelenterata, Annuloida, Proto- 
 zoa,, &c.) 
 
 Radiolaria (Lat. radius, a ray) A class of Protozoa, including tho 
 
 Polycystina. 
 
 \ Radius One of the two bones of the fore-arm of the higher 
 vertebrates. 
 
 Ramus (Lat. a branch) One of the halves of the lower jaw in 
 the Vertebrata. 
 
 Reptilia (Lat. repo, I creep) A class of Vertebrata, including 
 crocodiles, lizards, serpents, and tortoises. 
 
 Rhizopoda (Gr. rhiza, root; pous, a foot) A class of Protozoa 
 which have the power of pushing out pseudopodia. These 
 processes have the appearance of roots. 
 
 Rotifera (Lat. rota, wheel ; fero, I carry) A group of microscopic 
 animals belonging to the class Scolecida. The mouth is sur- 
 rounded by fringes of cilia, which, when in motion, resemble 
 a pair of toothed wheels. 
 
 Rugosa (Lat. ruyosus, wrinkled) An extinct group of corals. 
 
 v Sacrum The vertebrae which articulate with the haunch bones 
 to form the pelvis. 
 
 Sarcode (Gr. sarx, flesh; eidos, form) The jelly-like substance of 
 which the bodies of the Protozoa are formed. It is some- 
 times called protoplasm. 
 
 Scapula The shoulder blade. 
 
 Sclerobasic (Gr. sderos, hard; basis, the foundation) A term 
 applied to the red coral, because it is secreted by the united 
 bases of the polypes. 
 
GLOSSARY. 171 
 
 Sclerodermic (Gr. scleros, hard ; derma, skin) Applied to the 
 coral which is formed within the tissues of the reef-building 
 polypes. 
 
 Scolecida (Gr. slcolex, a worm) A class of Annuloida, including 
 the tape-Worm and other internal parasites. 
 
 Septa (Lat. partitions) Applied to the walls of the chambers in 
 the nautilus, &c. 
 
 Sertularida (Lat. sertitm, a wreath) A group of Hydrozoa. 
 
 Sessile (Lat. sedeo, I sit) Not supported upon stalks; the op- 
 posite of pedunculated. 
 
 Siliceous (Lat. silex, flint) Composed of silex or flint. 
 
 Siphon (Gr. a tube) One of the breathing tubes in the Mollusca. 
 
 Siphuncle (Lat. siphunculus, a little tube) The tube which con- 
 nects the chambers of the shells in some of the Cephalopoda. 
 
 Somatic (Gr. soma, the body) Belonging to the body. 
 
 Somite (Gr. soma) A segment of the body in the Annulosa. 
 
 Spermatozoa (Gr. sperma, seed; zoon, an animal) Minute or- 
 ganisms found in the sperm cells of animals. 
 
 Spicula (Lat. spiculum, a point) Applied to the needle-shaped, 
 siliceous bodies found in sponges, c. 
 
 Spinnerets The teat-like organs situated at the extremity of the 
 abdomen in spiders, &c., through which the threads that 
 form the webs are drawn. 
 
 Spongida A group of Rhizopoda, including the sponges. 
 I Sternum The breast-bone. 
 
 Stigmata (Gr. stigma, a mark) The apertures by which the 
 tracheae of insects, &c., communicate with the atmosphere. 
 
 Swimmerets Limbs attached to the abdomen in the Crustacea 
 which are used in swimming. 
 
 Tseniada (Gr. tainia, a ribbon) The group of Scolecida to which 
 
 the tape-worms belong, 
 i. Tarso-metatarsus A bone in the leg of a bird formed by the 
 
 amalgamation of the lower portion of the tarsus with the 
 
 metatarsus. 
 
 Tarsus The small bones which form the ankle. 
 Telson (Gr. the end) The somite at the extremity of the abdomen 
 
 in the Crustacea. 
 Test (Lat. testa, a shell) Applied to the calcareous covering of 
 
 the sea-urchins, &c. 
 Tetrabranchiata (Gr. tetras, four; branchiae, gills) An order of 
 
 Cephalopoda to which the pearly nautilus belongs. They 
 
 possess four gills. 
 Thalassa-collida (Gr. thalassa, the sea; kolla, glue) A group of 
 
 Protozoa. 
 
 Theca (Gr. theke)A sheath or case. 
 Thorax (Gr. a breastplate) The chest. 
 
172 ZOOLOGY. 
 
 ' Tibia (Lat. a flute) One of the two bones of the leg.^ 
 Trachea (Gr. tracheia, the windpipe) The tube which connects 
 
 the lungs with the mouth in the air-breathing Vertebrata. 
 Tracheae The air- tubes which ramify the bodies of insects, &c. 
 Trematoda (Gr. trema, a pore) A group of Scolecida to which the 
 
 "liver-fluke" of the sheep belongs. 
 Trilobites (Gr. treis, three ; lobos, a lobe) A group of extinct 
 
 Crustacea found abundantly in the Silurian rocks. They are 
 
 so called because their bodies were composed of three lobes. 
 Tunicata (Lat. tunica, a cloak) A class of Molluscoida which are 
 
 covered with a leathery case. It is also called Ascidioida. 
 Turbellaria (Lat. turbo, I disturb) A group of free-swimming 
 
 JScolecida. They are so called on account of the currents 
 
 produced by the cilia with which their bodies are covered. 
 
 ] Ulna (Gr. olene, the elbow) One of the bones of the fore-arm. 
 Umbo (Lat. a boss) The beak of a bivalve shell. 
 Univalve (Lat. unus, one; valvce, folding doors) A shell composed 
 
 of a single piece. Applied to the shells of the Cephalopoda, 
 
 and most of the Gasteropoda. 
 
 Vascular (Lat. vas, a vessel) Belonging to the circulatory 
 
 system. 
 [ Velum (Lat. a veil) The membrane which partly closes the disc 
 
 in the " naked- eyed >J medusce. 
 >- Ventral (Lat. venter, the stomach) Belonging to the lower surface 
 
 of the body. 
 
 Ventricle (Lat. venter) One of the cavities of the heart which 
 receives blood from the auricle, and drives it either to the 
 breathing organs or through the system. 
 
 V Vertebra (Lat. verto, I turn) One of the joints of the back-bone. 
 ^Vertebrata The highest sub-kingdom, characterized by the pos- 
 session of a back-bone. 
 
 Vesicle (Lat. vesica, a bladder) A little sac or bladder. 
 Viviparous (Lat. vivo, I live; pario, I bring forth) Producing 
 the young alive. 
 
 Zooid (Gr. zoon, animal; eidos, form) Applied to the individuals 
 which make up a compound organism. 
 
 Zoophyte (Gr. zoon ; pJmton, a plant) A term sometimes applied 
 to animals which resemble plants, such as the corals, sea- 
 anemones, sponges, &c. 
 
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