THE LIBRARY 
 
 OF 
 
 THE UNIVERSITY 
 OF CALIFORNIA 
 
 PRESENTED BY 
 
 PROF. CHARLES A. KOFOID AND 
 MRS. PRUDENCE W. KOFOID 
 
COLLARED MONADS (Clioano-flariellata). 
 
 1, Monosiga fusiformis ; 2, Codosiga alloides ; 3, C. grossularia : 4, C. urnbellata ; 5, C cymosi : 6, C. botrytis ; 7, Astrosiga 
 disjuncta; 8, A. mouiliformis ; 9, Salpinerseca marina : 10, S. ampulla : 11, S- Stemii : 12, S. napiformis : 13, S. Clark ii ; 
 14, S. vaginicola : 15, S. cornutum ; 16, S. tintinnabuluni ; 17, Lagenseca cuspidata ; 18, Polynseca dichotoma all highly 
 magnified. (Modified after Saville Kent and Stein.) 
 
 12 
 
15, V 
 
 TYPE PROTOZOA. CLASS INFUSORIA (INFUSORY ANIMALCULES). 
 
 Microscopic Animals One Cause of the Phosphorescence of the Sea and of the Discoloration of "Water The Life in 
 Infusions Characters of the Infusoria Example of Ciliate Infusorians The Slipper Animalcules Their Construction 
 The Flagellate Order Features Cercomonas The Cilio-flagellate Infusorians Characters The Animalcules of 
 the Ponds in Phoenix Park, Dublin Melodinium Ceratium The Order Tentaculifera Characters Acineta 
 Classification The Ectoplasm The Endoplasm Origin of the Cilia, Flagella, and Tentacles How Infusorians Feed 
 Action and Function of the Contractile Vesicle The Nucleus or Endoplast The Colours of Infusoria The Coloration 
 of Waters Trichocysts Reproduction by Fission, Gemmation, and otherwise Distribution TENTACULIFERA 
 SUCTORIA ACTINAEIA CILIATA HoLOTRiCHA Paramecium Prorodontidse Trachelocercidse Ichthyophthiriidse 
 Colepidse Ophryoglenidse Pleuronemidae Lembidae Family Discovered by Leidy Opalinidse HETEROTRICHA 
 The Largest Infusoria Spirostomum ambiguum Condylostoma, patens Stcntor polymorphus PERITRICHA Halteria 
 grandinella Urocentrmn turbo The "Bell" Animalcules Genera with Vorticella-like Animalcules HYPOTRICHA 
 CILIO-FLAGELLATA FLAGELLATA Noctiluca miliaris. 
 
 IP a glass tumbler be dipped into a pond or ditch, so as to collect some of the vegetation which is 
 found at the surface and at the sides, besides some clear water, it will invariably be found to contain 
 numerous living things, some of which are just visible to the naked eye, whilst others require a lens 
 or a compound microscope for their detection and examination. 
 
 The larger living things are mostly in rapid movement about the water, whilst some cling to the 
 small plants and wfeed. They are usually small Crustacea, and also the larvae and active nymphs of 
 insects. Sometimes a water-spider is included in the capture, and frequently small worms are to be 
 seen. Often just visible, and moving here and thei'e, are numerous animals which evidently produce 
 considerable currents in the water, and a lens enables the observer to distinguish that they belong to 
 species of Rotifera of the Vermes. 
 
 But the most numerous of the dwellers in the water are either, in a few instances, just visible to 
 the unassisted eye, or are to be seen in countless numbers with the 
 aid of high magnifying powers under the compound microscope. 
 Amoeba and Gromia, minute Rhizopoda, may be found on the weed 
 or on the glass which contains the water, and little moving things 
 are visible which the botanists state are of the nature of vege- 
 tables, such, for instance, as the globe-like Volvox. But besides 
 Crustacea, Insecta, Vermes, and Rhizopoda, and vegetable 
 organisms, there are thousands of microscopic, or nearly micro- 
 scopic, animals, which are called Animalculse, or little animals, 
 and also Infusoria, or animals which live in infusions. Suppose 
 that some sea- water is collected, with a piece of seaweed in it ; 
 after a few days a host of those minute microscopic animals will 
 be found in the slime around the weed. 
 
 On a warm summer evening, as darkness closes in, the ripples 
 of the sea become luminous, and flashes of light start from one 
 part of the harbour or coast-line, and stretch far and wide, expand- 
 ing in ever- widening circles. This particular form of phosphorescence of the sea is due to the presence 
 of myriads of minute animals, which do not belong to any of the groups of animals hitherto described 
 in this work, and which must be ranged amongst the Infusoria. Again, discoloration of fresh and salt 
 water often occurs, and it is found to be produced by crowds of microscopic creatures. In water 
 which is brackish, in water which contains a considerable quantity of salt, in water which may be icy 
 cold or very warm, and in water which is impregnated with foetid gas and decaying animal and 
 vegetable remains, these simple, active, wandering, or sedentary microscopic creatures, which constitute 
 the lowest forms in the animal kingdom, and which in some instances are separable only in a 
 very arbitrary manner from the simplest and lowest members of the vegetable kingdom of nature, may 
 be found in abundance. Place some of the pond water, deprived of its visibly living and 
 moving things, under a microscope with a low power, or such an one as will magnify about 
 forty times : minute bodies, hitherto invisible, are seen moving rapidly across the field of vision 
 (Fig. 1), sometimes rushing across, so that only an indefinite idea can be gleaned of their shape; or 
 283 
 
 Fig. 1. INFUSORIA IN THE 
 THE MICROSCOPE. 
 
354 
 
 NATURAL HISTORY. 
 
 going along more slowly, either steadily or turning over from side to side, and screwing 
 themselves, as it were, forwards. Sometimes a dozen or more will come within the range of 
 vision, and twist and turn in every direction, and suddenly rush off, moving so as not to come 
 in collision. Occasionally a globular-shaped thing will come by and stop, and just as suddenly 
 will leap, as it were, in the water, and go right out of sight. Now and then a great current of 
 water appears to be in motion, near the side of the field of vision, and if the slide holding the 
 water be moved, so as to bring it beneath the eye, some balls, like specks, are seen united to 
 delicate stems. They produce much movement in the water, and are suddenly dragged back- 
 wards towards their fixed point. Here and there, settled down and resting on a kind of stem, 
 some pear-shaped things may be seen, with delicate hairs sticking out from their ends. A still higher 
 power of the microscope, Avhich will < magnify from 300 to 1,000 times, enables other and smaller 
 creatures to be seen, and renders the minute structures, of the larger, visible and capable of study. 
 Amongst the smaller ones are little bag-shaped things, with one or two hair-like projections the cilia 
 
 which keep them in movement and in places here and 
 there are multitudes of little moving things, mere 
 lines of matter, with an end produced into a hair-like 
 tail or flagellum. These are amongst the simplest of 
 living things, and may be animal or may belong to 
 the lowest plants. The microscope reveals, amongst the 
 larger kinds, that they move in consequence of the 
 vibration, or to-and-fro movement of microscopic cilia, 
 and that the kinds which are stalked can be retracted 
 by the contraction of a granular tissue resembling the 
 simplest form of muscle. 
 
 If lately-collected rain-water is examined in the hope 
 of discovering any of these minute forms of life, disap- 
 pointment will occur. But if some hay, or any vegetable 
 matter, be allowed to soak in pure water exposed to the 
 air, or if pieces of flesh, brain, blood, or any animal 
 
 Fig. 2. PARAMECIUM AtlRELIA. 
 
 A, Lateral, u, ventral surface ; c, in conjugation ; cv, contractile 
 vesicle; n, nucleus; 6, oral aperture. 
 
 substance, be placed in water, and also exposed for a 
 
 day or two, a great many species of these animalcules, or Infusoria, the individuals being in 
 vast multitudes, will be distinguishable. Certain kinds of these animalcules are almost 
 invariably to be found in water in which particular vegetable or animal substances have been 
 soaked, and a succession of kinds is often observed to occur as the infusion gets old. The free 
 access of air is requisite for all this, and the hay and animal substances form the food of the minute 
 creatures, whose derivation is not from the minute structures or broken-down tissues of the plant 
 or animal. The air contains the extremely minute spores, or reproductive particles, whence the 
 animalcules spring. There is no spontaneous generation of these animalcules, and no turning of dead 
 animal or vegetable tissue into them. The term Infusoria, or animals of infusion, merely relates to 
 where they are to be found in most instances, but not invariably, and it must be carefully noted that 
 the animalcules are not derived from the infusions. Certain infusions suit particular kinds of 
 Infusoria, and these particular species are to be found in them. 
 
 The Infusoria are exceedingly simple in their construction, may be said to be uni-cellular, and 
 are allied, as Protozoa, to the Rhizopoda. There is this distinction, however, that whilst the majority 
 of the Infusoria move actively, and a great number are sedentary, or move during some part of their 
 life-cycle, they rarely have silicious or calcareous tests,* and the pseuclopodia, which sometimes exist, 
 never run together as they do in Gromia and Amoeba amongst the Rhizopoda. The body is usually 
 soft, and there are one or more contractile vesicles. A nucleus exists, and there are vacuoles which 
 contain food. The outside of the body is ciliated in a great number, has but one or two long cilia in 
 front in others, and one group has no cilia, but tubular processes project from the more or less 
 pear-shaped body, and really act as suckers. 
 
 The following are examples of the four great divisions or orders of the Infusoria, 
 
 * Haeckel has described some with tests. 
 
STRUCTURE OF THE INFUSORIA. 
 
 355 
 
 3. CERCOMONAS TYPICA. (Saville Kent.) 
 
 A, Adult; B I, different stacrep in tlic development. (.After 
 Dalliiujei- ana Drysduk.) 
 
 Pond water and artificial infusions of hay yield, as a rule, considerable numbers of a rather large 
 animalcule, which may be from -^th to T ooth of an inch in length. They are free swimmers and long- 
 bodied, being narrowish and bluntly pointed at one end, and more sharply at the other. They are flat 
 also, and there is a groove in the body extending from the left side of the front part of the body back- 
 ward and underneath to about the middle. Tkey are about four times as long as broad, and their shape 
 has given them the name of Slipper animalcules (Fig. 2).* They are not quite symmetrical fore-and-aft, 
 and the back and ventral surface can be distinguished. The whole of the body is covered with a fine 
 down of cilia of nearly or quite equal size throughout, which vibrate with considerable rapidity, 
 enabling the animal to move here and there rapidly, to turn round on its axis, to swim backwards 
 and forwards, and even to turn like a screw on its long axis, throwing the under part up and over, to 
 replace the back in its original position. As these animalcules, which have a yellowish-brown tint 
 by transmitted light, move vigorously along, they rush over the field of the microscope and re-enter, 
 and should there be a collection of vegetable mucus, numbers will come together and push in and 
 .amongst it, passing here and there, but never brushing 
 up against one another, so as to come into collision. It 
 is evident that they have some power of slightly altering 
 the shape of the body, and that the slit on the underside 
 has to do with the inception of food. The cilia, when the 
 animal is moving or comparatively still, form currents in 
 the water, and those in the neighbourhood of the slit 
 produce whirlpools, down which rush minute particles of 
 food. These pass down the slit, and enter the body at 
 a kind of mouth, and they there come in contact with 
 the soft inner substance composing the animalcule, and 
 sink into it, being surrounded by a drop of water. 
 Several of these morsels of food are to be seen lying 
 
 in clear spaces filled with water or food vacuoles, and as the whole of the soft internal structure 
 tends to move in an amoeboid kind of manner, the vacuoles change their places. This gave rise 
 to the false idea that the Infusoria were many-stomached, or " polygastrica," In this internal 
 substance, or endoplasm, some other things are to be seen. Firstly, there is an oval body 
 with a small dark spot in it, the nucleus or endoplast, and the nucleolus or endoplastule ; secondly, 
 there are two spots, one close to either end of the body, which gradually become more visible and 
 transparent, and suddenly shut up and disappear. They are the contractile vesicles, and it is 
 commonly observed that, if the animalcule is subjected to any pressure, these light spots present 
 rays passing from them into the endoplasm, so as to assume a stellate appearance. The opening and 
 closing of these vesicles are very regular. There is a most delicate tissue covering the whole animalcule, 
 .and another from which the cilia spring. They are elastic, and appear to be endoplasm in a less 
 watery condition. They form the ectoplasm. Between these layers and the minutely-granular 
 endoplasm is one of exceedingly' delicate rod-like bodies arranged point outwards, and they are called 
 trichocysts. 
 
 The animalcule evidently respires through its outer ciliated coat, takes in food through the mouth 
 at the bottom of the slit, has several food vacuoles, which finally come near the surface skin, and dis- 
 charge the undigested matters. As the food, consisting of minute spores and animal and vegetable 
 matters, is digested, the protoplasm of the body is added to, and the circulation and removal of effete 
 matters are in relation to the contractile vesicles. 
 
 The creatures languish if the water remains too long without exposure to air, but otherwise their 
 movement appears to be constant. Occasionally two will approach and cling together by their oral 
 or ventral surfaces, and it is occasionally noticed that a large individual contracts midway and finally 
 separates into two. If watch be kept long enough, the animalcules will be noticed to become quiet, 
 to take 011 a globular form, and to have the ectoplasm dense and non-ciliated. Sooner or later the 
 globe will burst, and a host of minute moving things will come forth, each of which is a young 
 animalcule. 
 
 * Paramccium aurelia. 
 
356 
 
 NATURAL HISTORY. 
 
 This is a common instance of the order of the class Infusoria, called, from the body being more 
 or less covered with cilia, the INFUSORIA CILIATA. 
 
 The highest powers of the microscope, and glasses possessing very perfect defining qualities, are 
 requisite in order that the next type of Infusoria may be seen perfectly. The little creatures are free 
 swimming, and the body is long, egg-shaped more or less, but it has a projection so as to render it more 
 or less spindle-shaped or fusiform. In front, there is a single filament prolonged from the body like a 
 very large cilium, and a longer one, about twice the length of the body, projects behind. These are 
 the flagella. There is a single minute contractile vessel in the body on one side, and the nucleus or 
 endoplast is spherical, and near the centre of the animal. There is no mouth or special aperture for 
 food, and there are no cilia on the soft external part, which barely differs from the inner mass of the 
 minute body or endoplasm. Only measuring from YTTOTT*^ to TsVo* n ^ an nicn ^ n l en gth, these minute 
 Infusoria are found in vegetable infusions. They swim freely by means of their long flagella, and 
 also crawl over substances very much after the fashion of Amoebae. It may happen that one may be 
 seen larger or broader than the others, and, after a while, the observer is repaid by seeing the body 
 
 . 4. GENERA OF CILIO-FLAGELLATE INFUSORIA. 
 
 A, Melodinium uberriraum: n, Glenodinium acuminatiun : c, Diplopsalia lenticnla: D, Gymnodinium spirnre; B, Ceratiura tripos; F. Peridiniuni 
 talmlatuiu : G, Ceratium loiigicornc; H, O. fusus; I, Stephanomonas locellus ; J, Mitophora dubia; K, Heteromastix proteiforniis; 
 \., Mallomonas Plosslii. 
 
 split down its length, and two creatures swim off, each supplied with a front and rear flagellum. If 
 two come in contact, they join together, like Amoeba, and after a while the mass loses its flagella, and 
 a vast number of spores are formed out of the endoplasm. These escape, and gradually form into 
 creatures like those which produced them. 
 
 Exceedingly minute particles of food are taken in by the surface of the body at no particular spot, 
 and the undigested matters simply pass through the endoplasm to the outside. This Infusorian is a 
 Cercomonas* (Fig. 3), and is a fair example of the order called the FLAGELLATA. Members of this 
 order are distinguishable in some instances with difficulty from moving spores of the lower plants, 
 and indeed it is in this group that the junction of the animal and vegetable kingdoms is to be 
 found. The Flagellata contain very simply-constituted organisms, and some which are less so, and of 
 these last the phosphorescent marine Noctiluca is an example. 
 
 Another type of Infusoria combines, as it were, the characters of the ciliated animalcules and 
 those which have a flagellum. The kinds which are associated with it are mostly found in sea water, 
 and in many parts of the globe. A few, however, are to be noticed in fresh water in the United King- 
 dom. Thus, Professor Allman found enormous multitudes of an Infusorian about -5-^0^ to unnj^h ^ 
 an inch long, of a reddish-brown colour, in the ponds in Phoenix Park, Dublin. It had an almost 
 globular body, with a constriction or furrow running round the middle, and a groove passing from this 
 furrow over the body to the top. The whole surface was covered with extremely delicate moving cilia, 
 and a long, slender, active cilium or flagellum was found to be placed 011 the top in the groove. A large 
 endoplast (nucleus) was in the centre of the animal, and just below the origin of the flagellum was a 
 small, intensely red spot. A contractile vesicle occurs in this type. The brown colour of the ponds in 
 
 * Cercomonas typica. 
 
ORDERS OF THE IXFUSOR1A. 357 
 
 1854 was owing to the presence of prodigious numbers of this species of Melodinium* (Fig. 4, A). The 
 tint was sometimes uniformly diffused through the water, and at others was collected in dense clouds, 
 vary ing- from a few to upwards of 100 square yards in extent. Later on, the coloration of the ponds, 
 brought about by the agency of these minute organisms, had much increased in density. By the 9th 
 of July the water was so dark and brown, that a white disc, half an inch in diameter, was invisible when 
 plunged to a depth of from three to six inches ; while a copious exit stream, constantly flowing away 
 from the ponds, presented a similar deep brown hue. In many places the animalcules had descended 
 from the surface, and were found congregated in immense masses near the bottom of the water. In these 
 instances they had, for the most part, become quiet ; the flagellum and cilia had disappeared, and a kind 
 of transparent tissue had been developed around each one. During the life of these curious animalcules 
 the body divides across, and two individuals are formed ; and this proceeds time after time, adding 
 rapidly to the numbers of individuals. Moreover, the encysted state is accompanied by a breaking- 
 up of the internal protoplasm or endoplasm into numberless particles, each of which will grow into a 
 form resembling the parent. 
 
 In examining the phosphorescence of the sea, moderately large animalcules of -g^th of an inch 
 long are occasionally seen. They are light-emitting, of a yellow colour, and have a remarkable shape 
 and construction. An external coat, transparent but hard, exists, and it covers the soft structures. 
 It is prolonged into a long horn in front and behind, and the body is nearly globular, with a depression 
 around it, and a groove crossing this at right angles. The appearance is very peculiar. Cilia 
 bound the depression, and a very long and delicate flagellum, which moves like the lash of a whip, 
 starts from the groove. The long fore-and-aft projections are quite stiff, and the only mobile parts 
 are the cilia and flagellum. This Infusorian belongs to the same order as the last, and to the genus 
 Ceratiumt (Fig. 4, n). They are CILIO-FLAGELLATA. 
 
 A very different kind of animalcule must be taken, as the example of the next and last order of 
 the Infusoria. If the surface of water-plants in the Birmingham and Stratford Canal, for instance, be 
 observed, a fine Infusorian -^th to y^th of an inch in length may be seen fixed on a long stalk which 
 is straight and stiff. The body, placed at the top, is contained in a cup-like sheath, with a triangular 
 outline, widest where free, and where there is a slit which enables the endoplasm 
 to communicate with the water outside. The endoplasm (finely granular) does not 
 fill the cup, but collects in an egg-shaped mass which has a contractile vesicle, and 
 the nucleus or endoplast is in the form of a band. There are neither cilia nor a 
 flagellum, but a bundle of numerous tentacles exists at both ends of the free end 
 of the cup-shaped sheath, and they are processes of the body. The tentacles have 
 a disc-like top, and do not move so as to enable the animal to swim. They are 
 catchers of prey, and any small animalcule coming in contact with them is stopped, 
 and its delicate tissue is penetrated by their sucker-like disc (Fig. 5) J. By-and-by 
 the endoplasm of the victim is sucked out of it, and acts as the food of the catcher. 
 The young of these stationary Infusorians are active, and move well and rapidly 
 with the aid of cilia, and thus resemble the Ciliate Infusoria. These Infusoria -p. . _ 
 constitute the order TENTACULIFERA. TUBEROSA, WITH 
 
 There are, then, four great groups or orders of Infusoria typified by the TENTACLES EX- 
 
 -n 'ft TJT i T i A 1 PANDED AND CON- 
 
 species of the genus .raramecium, Cercomonas, Melodinium, and Acineta, and TRACTED. 
 they constitute the orders Ciliata, Flagellata, Cilio-flagellata, and Tentaculifera. 
 
 A host of species, included in numerous genera, is classified under each of these orders, and there 
 is the greatest diversity of shape and of method of life amongst them ; but the main features and especial 
 characters of the orders are so definite, that there is no difficulty in classifying any Infusorian, which 
 has attained adult age, in its proper group. 
 
 From their great vivacity of movement, their many varieties of cilia, the invariable existence of 
 contractile vesicles, and endoplasts, and sometimes trichocysts, the Ciliata, or the Infusoria which 
 move by and are more or less covered with cilia, strike the observer as of predominant zoological 
 importance. They are clearly more highly organised than the Infusoria which have only flagella. 
 And these last appear to be lower in the animal scale than the creatures which have a few cilia, 
 * Melon, a peach ; dine, a vortex. f Ceratium fusus. Acineta tuberosa (Ehrenberg). 
 
NATURAL HISTORY. 
 
 \ 
 
 and a flagellura also. The fact that the Tentaculifera are totally unlike the other Infusoria in their 
 adult age is very remarkable ; but it is evident that before they attain maturity they resemble 
 the Ciliata. New structures are thus, by evolution, given to the Tentaculifera, and they have 
 considerable affinities with the Rhizopoda. Their adult form is in advance of the ciliate young 
 
 one, and the order Tentaculifera must stand at the 
 head of the Infusoria. Next come the Ciliata, then 
 the Cilio-flagellata, and, finally, the Flagellata. 
 
 The Infusoria are uni-cellular, and this is true 
 where there are two or more individuals in close 
 contact, or where a common stem supports the 
 bodies of others, which may be numerous. For in 
 these instances subdivision of the parent has pro- 
 duced the independent creatures. In the Tenta- 
 culifera, however, the most highly-organised 
 amongst the Infusoria, in the species called 
 Dendrosoma radians (Fig. 6), there is a root com- 
 mon to many trunks which give origin to branchlets 
 terminating in a bundle of tentacles with suckers. 
 This arrangement can hardly be called uni-cellu- 
 lar ; there is, however, no actual cell division, and 
 indeed the ordinary idea of the single cell is hardly 
 applicable to this and many other Infusoria. 
 
 The simplest Infusoria belonging to the Flagel- 
 lata, which have no special spot for the ingestion 
 of food,* have no distinct environing membrane 
 over their soft finely granular protoplasm, and they 
 can assume various shapes for a while. Others 
 belonging to the same group have the outside of the 
 
 body slightly more solid than the rest. In the Ciliata the presence of an outer membrane is evident, 
 and it is possible to distinguish, on some of them, four layers around the soft semi-fluid central 
 eiidoplasm. On the outside is a perfectly transparent structureless membrane, and it is a true cuticle. 
 It forms a sheath for the stalk of some Infusorians, and the covers or shields (lorica) of others 
 (Fig. 7). It is composed of formed material, and is independent of the nutrition of the animal 
 Under the hyaline outer layer there is, without exception amongst the Ciliata, a 
 firm homogeneous elastic and contractile layer, of which the cilia and their various 
 modifications are the offshoots. They penetrate the outer layer and arise from this 
 inner one. In some, but not all, of the Ciliata, there is a layer beneath this last 
 one, which is more or less fibrillar, and highly contractile. It is the muscular, or 
 myophan layer of Haeckel. In the genus Stentor (p. 367) it is highly developed, and 
 it can be seen, by using high and well-defining powers, in the common Vorticella, in 
 which it forms the central, or contractile, part of the stalk, and a thin layer con- 
 tinuous with this is in the body. The fourth layer is not invariably found, but 
 it has been already noticed in the description of a Paramecium. It produces and 
 holds in place the minute rod-like bodies called trichocysts, which will be noticed 
 farther on. These layers constitute the ectoplasm. 
 
 The endoplasm, situated within the ectoplastic or outer layers, is more or less 
 fluid, granular, and coloured glairy protoplasm. It is tolerably immobile in many 
 Infusoria. In most it is subject to amoeboid movements, to a faintly-developed 
 rotatory movement, and to what may be called streaming. In some instances the movement is 
 strong, and resembles that of the cyclosis of plants, as in Yallisneria and Chara. Noctiluca, the 
 phosphorescent flagellate Infusorian, has the endoplasm more or less in the form of a network, 
 with vacuole spaces, and a quantity of granular substance, and this condition is seen in other forms. 
 
 * Group Pantostomata 
 
 Fig. 6. DEXDROSOMA EADIANS. (After SavilleKcnO 
 
 a, Embryos escaping with cilia; 6, buds producing embryos like the 
 parent ; st, stolon. 
 
 Fig. 7. TINTIX- 
 NUS LAGE- 
 NIJLA, SHOW- 
 ING THE 1.0- 
 1UCA AND THE 
 CKOWX OF 
 
 CILIA. 
 
NATURE OF THE CILIA, FLAGELLA, AND TENTACLES. 
 
 The spaces occasionally seen in the endoplasm, and which transmit light more readily than 
 the rest, are called vacuoles; they may exist as spaces tilled with water, and usually they con- 
 tain, besides the water, a greater or less portion of the vegetable or animal matter which has been 
 introduced into the body as food. They must not be confounded with the contractile vesicle. 
 Besides these, there is the nucleus or endoplast, which is surrounded, in part, by the granular semi- 
 fluid endoplasm, and which is also in contact with the 
 deeper layers of the ectoplasm. Colouring matter, diffused 
 or localised, is seen in the endoplasm, and this inner pro- 
 toplasm produces the minute particles or spores which escape 
 and develop into new individuals. 
 
 In all Infusoria, the cilia and their varieties, the flagella 
 and the tentacles are extensions of the substance of the 
 body. In the minute flagellate animalcules the flagellum, 
 which is an elongated whip-like cilium, is an extension of 
 the delicate ectoderm : in the Ciliata the cilia arise from 
 the special layer beneath the hyaline cuticle ; and the long 
 suckers of the Teiitaculate order are probably extensions of 
 the same tissue. The cilia differing in dimensions and 
 shape in some Infusoria are the minute hair or eyelash- 
 looking vibratile appendages which mainly move their posses- 
 sors, or produce currents in the water when the Iiifusoriaii F *S- 8. A, B, STYLONYCHIA MYTILUS, SHOWING 
 
 ! ml ,. , -.. .. CILIA. STYLES, AND UNCINI J C. EUROLEPTUS. 
 
 is fixed. They appear to move actively in one direction, lAfUr stein ) 
 and to return to their original position by their elasticity. 
 
 The tops move forwards and backwards, and it is noticed in certain species that the ciliary lashing is 
 consecutive in a series, and that it produces the appearance of rotation, as in the Rotifera (pp. 24.5-9). 
 They are semi-solid and elastic, and they are moved by the contraction of the endoplasm at their base. 
 The vibratile cilia are arranged in. bands only, in certain families, and universally in others. Some 
 Infusoria have some cilia which are elongate, flexible, but not movable, and they are then called 
 setfe ; and in one interesting genus (Halterici) these long hairs are utilised when the animal makes 
 its sudden jumps. Some Ciliate Infusoria have these setae stout, and placed on the ventral, or 
 uiider-surface of the body, or at the extreme ends, and then they are called styles. In some instances 
 the ends of the styles are branched or feathered. In a family of the Ciliata, the Oxytrichidfe (p. 371), 
 there are claw or sickle-shaped appendages, which are modified setae, called hooks, or uiicini, and some 
 of the species carry all these remarkable outer structures for the purposes of locomotion and pre- 
 hension (Fig. 8). The body is, in some Infusoria, furnished with fin-like, thin, vibratile membranous 
 fringes (Fig. 9), and in one important group of the Flagellata the collar of the animalcule, which 
 exactly resembles that of the cell of the sponge, has its protoplasm in streaming movement, which 
 carries the particles coming in contact with the outside over the top to the mouth within. The 
 tentacles of the Tentaculifera resemble the pseudopodia of Rhizopods more or less ; some have a disc- 
 shaped sucker at the top, and are hollow, being filled with semi-fluid eiidoplasm. A spiral fibre 
 is seen 011 the outside of some tentacles, and in one family there are no terminal suckers. 
 
 Whilst some Infusoria take in food at any part of their body, the morsel simply sinking into the 
 soft protoplasm, and carrying with it a small quantity of water, forming thus a vacuole, in others it 
 
 is carried in the direction of a particular orifice, slit, or tubular 
 cavity, by currents in the water produced by certain cilia. In 
 some species the mouth-opening is always visible, in others it is 
 small, and only visible at the time of the capture of prey, and in 
 a few it is so large that a morsel is often swallowed nearly as large 
 as the captor. The mouth, in the most perfect forms, consists of a 
 
 passage in the ectoplasm structures, which can dilate, and the lining of which is plaited, folded, and 
 even furnished with a layer of rod-like teeth (Fig. 10). This part is often capable of protrusion, and 
 on opening it leads to the exposed semi-fluid endoplasm, and not to anything like an oesophagus and 
 stomach. The morsel simply sinks into the mass with a little water, and forms a vacuole. 
 
360 
 
 NATURAL HISTORY. 
 
 Fig. 10. A, PRORODON MARGA- 
 
 RITIFER; B, PHARYNGEAL ROU- 
 FASCICLE OF P. NIVEUS C, 
 DITTO OF NASSXJLA. 
 
 cv, contractile vesicle ; n, nucleus. 
 
 One or more food vacuoles may exist, and as one is formed subsequently to the other, the oldest 
 
 vacuole is the most deeply imbedded, and if the animalcule be fed with carmine, a number will be 
 
 noticed forming a series in the endoplasm, and moving with. it. Much of the food thus received is 
 
 digested, and the rest is evacuated in a definite direction, and sometimes through a special opening 
 
 in the ectoplasm the anus. In many species, however, the faecal matters pass out at any point. 
 
 When one of the Infusoria is lively and feeding, and is being examined under high powers of the 
 microscope, one or more spots, with a circular or radiating outline, will 
 suddenly appear near the ends of the body. Each begins in a point 
 of greater transparency than the body structure all around it, increases 
 rapidly in diameter, and often assumes a tinge of colour, retaining, how- 
 ever, its transparency. It is a light-transmitting space, with the slightly 
 denser structure of the inside of the animal around it. As the light 
 from the reflecting mirror of the microscope traverses the tissue of 
 the Infusorian at this now enlarged spot, it seems to be unsteady, and 
 this depends upon water passing into this really globular space, which, 
 seen \mder the microscope, presents the appearance of a circular area 
 (Fig. 11, A, cv). It is evident that water flows into this space, which is 
 situated really in the layer immediately over the soft endoplasm ; 
 there is no environing membrane to it. Suddenly the circle of light 
 
 closes in on its centre, and the appearance of a light point amongst the darker surrounding 1 
 
 matter suddenly ceases. The tissue closes in on the space, moving in on all sides, and this is done 
 
 not passively but actively, for in some instances a tremor can be seen to occur over the whole 
 
 animalcule at the time of the contraction of the space. Moreover, although the space enlarges slowly, 
 
 it contracts very rapidly, as a rule. If the Infusorian be kept for some time under observation, the 
 
 absence of food and fresh water will begin to diminish 
 
 its energies, and it will especially influence the rapidity 
 
 of the dilatation and subsequent contractions of this 
 
 space, which is termed a contractile vesicle. The 
 
 appearance of the light spot is not so frequent ; it 
 
 commences languidly, and enlarges slowly, and finally 
 
 contracts, or disappears less abruptly than in the 
 
 instance of the vigorous animal. After a while, 
 
 the appearance and disappearance of the spot or, 
 
 in other words, the dilatation and contraction of the 
 
 contractile vesicle become slower and irregular, and 
 
 they cease with the death of the animal. 
 
 More than one contractile vesicle may exist 
 
 in the same species, and their position in the body, 
 
 although generally well defined, is not invariably in 
 
 the same spot. Usually, the vesicles are nearer the 
 
 ends of the body than the central part, and when Fi g- n A > niAGRAM OF BTICELIA NEBULIFERA : 
 
 J . B-D, PHASES OF LONGITUDINAL FISSION J E-F, 
 
 they are fully dilated they occupy not only a portion PHASES OF ATTACHMENT, AND G-H, OF INCORPORATION 
 of the body hitherto filled with endoplasm, but come 
 
 . ,, , , ,. T ., . 
 
 close under the outer and denser tissue. In the in- 
 
 d, disc: p, peristome; 7, gullet: c, contra 
 
 stances where the contractile vesicle presents the ^parUcTes? 31 ' Thearrow9d ' 
 appearance, under the microscope, of a circular space, 
 
 no movement can be seen, in the vast majority of observations, to extend from it into the 
 endoplasm during the active contraction or dilatation. The water contained in the vesicle must 
 go somewhere, and must be derived either from within the body or from without, or perhaps 
 from both directions. Occasionally, however, a very indistinct movement can be seen radiating, as it 
 were, amongst the granular, or almost homogeneous protoplasm of the animal, subsequent to an active 
 contraction of the space. No visible movement accompanies the infilling. There are many Infusoria, 
 such as the species of Paramecium, in which the contractile vesicle, when fully expanded, is not limited 
 
 OF FHEE EMBRYO OF V. MARINA (After Greeffe) ; 
 
 I, ENCYSTED STAGE OF V. MICROSTOMA. 
 
 , gullet: c, contractile vesicle: n. nucleus : 
 
THE NUCLEUS OR ENDOPLAST IN THE INIUSORIA. 
 
 by a definite circle of endoplasm, but has rays, or tubular passages, tapering outwards around it 
 (Fig. 2, cv). The passages are numerous, and may be seen to ramify at their extreme ends, and they 
 are weak spots in the cortical layer over the more fluid endoplasm, extending far and wide from the 
 vesicle. These passages transmit light more readily than the protoplasm in which they are placed, 
 and it therefore occurs that, as water fills them, and they increase in diameter and length, they are 
 nearly as light-transmitting as the main space with which they are continuous. They become largest 
 just before the contraction of the vesicle, and they sometimes do not disappear until after its 
 contraction. It is evident that the watery contents of the passages are pressed upon by the con- 
 traction of the surrounding protoplasm, and that this water and that of the space penetrate, 
 during contraction, into this environing substance. Movement may be noticed under the outer 
 tissue, here and there, within and along the lines of the passages. More or less defined com- 
 munications exist between the outside water and the contractile vesicles through the ectoplasm, 
 and the vesicle receives pure water from without, and collects 
 and expels the impure water from within the animal. It is 
 evident that the function of the contractile vesicle is of great 
 importance to the animal, and it may relate to the elimination 
 or removal of certain soluble matters resembling the urinary 
 secretions. It may also relate to an internal circulation of water. 
 
 The rhythm of the dilatation and contraction is very 
 remarkable, and Saville Kent states that "the time occupied 
 between the consecutive pulsations of this organ is found, 
 under normal conditions, to present a constant average among 
 individuals of the same species, varying from a few seconds only 
 in certain forms, to over sixty or even one hundred seconds in 
 other types." 
 
 The nucleus or endoplast with its contents resembles, in 
 some Infusoria, that of the simplest vegetable cell. In its 
 simplest form, noticed in some of the Flagellata, the endoplast is 
 more or less spheroidal, and may or may not contain a nucleolus 
 or endoplastule. Saville Kent has given an admirable resume 
 of the knowledge which has been accumulating regarding these 
 structures, and he notices that the first step towards complexity 
 is in the genus Euglena and its allies, in which the endoplast 
 becomes ovate in outline. A sausage shape is assumed in 
 some Ciliata, and its ribbon shape in Vorticella has long been 
 
 known. In some of the Tentaculifera the nucleus is branched, and in some Ciliata, such 
 as Condylostoma patens (Fig. 12), it presents a necklace appearance, and in others the swellings 
 are widely separated by narrow processes. More than one endoplast exists in the Oxytrichidae, 
 one being in front and the other behind the centre of the body ; and in some species of Opalina 
 the endoplasts are numerous. In its more complex forms the endoplast is enclosed within a 
 very delicate transparent membrane. The nucleolus or endoplastule is sunken within the substance 
 of the endoplast in some forms ; it is attached to the inside of the membrane of the endoplast 
 in others, and on the outside in a few Infusoria. 
 
 Two or three endoplastules exist in some, and in Vorticella they are granular fragments, one or 
 more of which become enclosed within each of the segmental portions into which the endoplast 
 becomes separated, during the process of internal budding, which will be noticed farther on. 
 The endoplast is in contact with the softer internal substance of the Infusoria (the endoplasm), and 
 also with the inner part of the cortical structures or ectoplasm. 
 
 The Infusoria are usually more or less coloured, and the Flagellata, with rare exceptions, have 
 a small brilliant crimson spot at one end of the body ; in one genus there are two of the spots. 
 Amongst the Ciliata the red spot is rarely seen, and one genus has a black one ; but the Tentaculifera 
 do not have these pigment spots. Formerly they were considered to have to do with vision, but this 
 is an error, and the common term " eye spot," is therefore incorrect. Diffused colouring matter tints 
 284 
 
 Fig. 12. COXDYLOSTOMA PATENS, SHOW- 
 ING MONILIFORM ENDOPLAST. 
 
362 NATURAL HISTORY. 
 
 most Infusoria, and the smallest animalcules or monads belonging to the Flagellata have a pale 
 glaucous or liuorescent hue, and Saville Kent notices that this is visible under high magnifying 
 powers. It is probably due to reflected and not to transmitted light. Most of the Flagellata are 
 coloured, and the species of one great group, the Euglenidse, are of a brilliant green, the colour 
 being diffused in the endoplasm. The colour is identical with that of the lower plants, containing 
 chlorophyll, and it is remarkable that this green tint should turn to red. Thus in Astasia sanyuinea 
 the green colour, which gives a tint to the water in which the myriads of the animalcules swim, is 
 suddenly turned to red, accounting for old and new traditions regarding the turning of fresh waters 
 into blood. Ray Lankester has shown, that in the genus Stentor the green matter, like that of 
 Hydra viridis and Sponyilla, is a chlorophylloid substance similar to that of plants. One Stentor, 
 however, has a blue colouring matter which is produced by a special chemical combination called 
 Stentorin. Quite as many Infusoria have a diffused pale amber to deep olive colour as green, and 
 most of the Tentaculifera and Cilio-flagellata have these dull colours. 
 
 Saville Kent notices that some of the Flagellata differ from the majority by the presence of 
 the olive colouring on two lateral bands on the body. In the Ciliata, a Leucoplnys is of a 
 brilliant crimson colour, and a Nassula has numerous violet granules in its endoplasm. Minute 
 crimson granules have also been noticed in the contractile tissue of the stalk of Vorticella. 
 
 In some Euglenida?, thei'e are bodies in the green endoplasm which are of a starchy nature. 
 Finally, there are the accessory structures of the cortical part of some of the Infusoria or the 
 trichocysts. As has been already noticed (p. 355), they are visible in Paramecium aurelia, in 
 the form of very slender rods crowded together in a layer, their points looking outwards beneath 
 the outer cuticle. Under the action of weak acetic acid, these trichocysts force through the 
 cuticle and beyond the cilia. Ellis, an Englishman, writing more than a century since, discovered 
 these curious bodies ; and Allman, in 1855, established their true nature, and assimilated it to a 
 certain extent with that of the iiematocysts of the Corals. But there are essential distinctions. 
 Allman found that the minute fusiform rods, under external irritation, become suddenly transformed 
 into long hair-like filaments, which projected from the whole surface. By carefully crushing 
 examples, and isolating the trichocysts in their unaltered condition and in their fusiform shape (that 
 is, swollen in the middle, and narrow at each end), it was found that after a few seconds the shape 
 was altered with a jerk, as if some previous state of tension were relieved. A spheroidal shape was 
 assumed by the hitherto fusiform i-od. Then, in a few seconds, a spiral filament was observed to 
 become rapidly evolved from the sphere, apparently through the rupture of a previously confining 
 membrane. The spiral fibre unwound, and became straight and rigid. In their most extended state, 
 these bodies were found to consist of a long rigid spiculum-like half, sharp at one end, and continued 
 
 at the other into a very filiform part, which is bent more or less. 
 Probably they have a noxious influence on minute living things. 
 
 Some Infusoria appear to retain the same shape under all kinds of 
 circumstances ; others enlarge laterally or longitudinally, and even twist, 
 as they move here and there or endeavour to get in between substances, 
 but they speedily return to their normal figure. Such irregular changes of 
 shape as are seen in the Amreboids are not often found in the Infusoria, 
 but a very different appearance is presented by some during active motion 
 and feeding and during quiescence. 
 
 Flg 13 (4fls LE *L" IR Nothing is more common than to see many Ciliated Infusoria moving 
 
 A.showing^-namonuHon^, along with the shape of their bodies altered by the presence of a greater 
 
 or less central constriction, and if one of them is watched, it will be seen 
 
 to separate, into a front and a hinder part, and each will become a separate individual 
 (Fig. 13). Division also occurs length wise. It has been computed that, in the instance of 
 Stylonyckla mytilus (p. 371), no less than a million of independent beings were derived 
 from repeated fission of a single individual in the course of ten days. When Infusoria form 
 colonies, they arise from the repeated binary subdivision of the fii'st stock, and in some instances 
 masses result, slime-like, many feet in extent (Epistylis grandis, p. 370). In the majority of species, 
 the division is across the body, and in others in a longitudinal direction, especially in the 
 
REPRODUCTION OF THE INFUSORIA. 
 
 363 
 
 Vorticellidse. In the Stentors and some other genera the fission is oblique. The endoplast divides 
 in every instance, and part remains with each individual, and the other organs, such as the mouth, 
 anus, and contractile vesicle, are developed where they are wanting. 
 
 Some Infusoria increase by a process resembling budding, and in this process, the important 
 endoplast contributes a little process which accompanies the protrusion of the body membrane to form 
 the bud. In Noctiluca (p. 374) the protoplasm beneath the cuticle becomes broken up into nodular 
 fragments, which are protruded upon the external surface, and are finally liberated as very minute 
 bodies resembling monads, and these grow into adult Noctilucae. 
 
 In some instances the young grow within the body of the parent, but only at the expense of the 
 endoplast. Portions of this separate and become embryos, which escape with their cilia, and either 
 resemble the parent or grow into its shape as in the Teiitaculifera. 
 
 Another method of reproduction is when the Infusoria become quiescent ; a delicate covering 
 is then formed over the body, and the quiet and encysted creatures have their internal tissue broken 
 up into my rinds of minute particles, which escape, and 
 finally assume the shape and destiny of the parent. It 
 is found that sometimes an intermediate amcebiform con- 
 dition occurs (Fig. 14). 
 
 Infusoria also reproduce after a process which some- 
 what resembles the conjugation in Algae amongst plants. 
 Swimming, or fixed by a common stalk, two animalcules 
 come in contact by their oral surfaces, and remain united 
 for a limited period. They swim about, and exist as one, 
 and in the Flagellata the flagella are withdrawn, and 
 anio3biform processes are cast forth. In other instances 
 the junction of different individuals, one often larger 
 than the other, persists. Under both circumstances the 
 reproductive energy of the couple is intensified. How, 
 is a matter of debate, but late microscopical researches 
 
 by Biitschli and Englemann show that during the process the original endoplast in both 
 animalcules breaks up into a number of fragmentary portions, and becomes lost among the 
 endoplasm. By-and-by a new endoplast is constructed through the gradual assemblage and 
 union with each other of fragmentary particles, and the new endoplast is common to both of 
 the animalcules when the conjugation is complete and lasting, as in Vorticella (Fig. 11) ; 
 while two or more, according to the normal number, are reproduced where the conjugation is 
 transient as in Paramecium (Fig. 2). Biitschli denies that embryos are subsequently developed from 
 the endoplasts, and he considers that the conjugation is a mere vital stimulant to the decaying 
 energies of the animalcule. Before passing on to a short classification of the Infusoria, it is necessary 
 to mention that they have a most extraordinary distribution. Some families inhabit salt water, 
 others fresh ; some species live in running water, others in stagnant pools. Many species are parasitic 
 on, and others within, other Infusoria, and many groups of Iiivertebrata and Vertebrata. Many 
 are only found in animal, others in vegetable, infusions. One group is mouthless and essentially 
 endoparasitic. The Opaliiiidae inhabit the alimentary canals of insects, frogs, toads, and the 
 aquatic Annelida. Some Ciliata inhabit the stomachs of ruminants, some live in the human gut. 
 Others live fixed to fish, or crawl about the Hydra. The Flagellata are found in fresh and salt 
 water, and are often parasitic, and some inhabit human urine. In searching for ordinary and 
 well-known forms, the surface of pure and coloured fresh waters, and the leaves of the plants, should 
 be examined, and the waters of bogs and the sea-shore yield many new forms. The artificial 
 production of Infusoria, by infusing hay, meat, &c., depends on the existence of the germs in the 
 air, in the water, and collected about the plants. 
 
 ORDER TENTACULIFERA (IIuxle.y\ 
 
 An example of this order has been noticed already, and it explains the characters of the group. 
 They are animalcules inhabiting either salt or fresh water, and many are parasitic on and within other 
 
 14. 1CHTHYOPHTHIRIVS MULTIFILIIS. 
 
 (After Fouquet.) 
 
 A, Adult ; B-G, difforont stages of development (.E, escape of 
 young); H, oral apparatus. 
 
364 
 
 NATURAL HISTORY. 
 
 Invertebrata. They have tentacle-like processes, derived from the cuticle or from the endoplasm, 
 or from Loth of these parts. The body contains an endoplast and one or more contractile vesicles. 
 They increase by division across or longitudinally, and also by budding, which may be external or 
 internal. Some of the young (embryos), on escaping from the parent, are ciliated, and the cilia 
 may be arranged over the whole body, or in the form of a wreath around the body, or only on 
 the under surface. With growth the state changes, and the cilia are lost. Others resemble the 
 parent. The adults have neither cilia nor flagella. The majority of species are sedentary. 
 The Tentaculifera are divided into two sub-orders, in one (the Suctoria) the tentacles are wholly 
 or partially suctorial in their office, and in the other (the Actinaria) they are not suctorial but 
 merely adhesive. One family of the first sub-order has one or two tentacles only, and another 
 (the Acineta) has many tentacles, and some of the genera have the body without, and others with 
 a lorica or a more or less covering sheath. Acineta tuber osa has the tentacles in bundles, which 
 protrude through the transparent lorica, and the endoplasm can be seen within. It is a salt water 
 form, and measures from -~\Q\\\ to -g^th of an inch in length (Fig. 5). 
 
 These animalcules remain with their tentacles extended, and other freely-swimming minute 
 Infusoria are stopped by the suckers at their tips. The endoplasm of the victim passes into 
 the hollow of the tentacle and mixes with the soft tissue of the body of the Acineta. A third 
 family includes the genus Dendrocometes, which settles on Gammarns puLex, and has rather flexible 
 tentacles slightly branched at their extremities. Its embryos, which escape from the parent, 
 are ciliated underneath only. The next family includes branching Acinetans, with many tentacles, a 
 
 host of individuals apparently arising from a 
 common stem. But the tops of the ramified stem 
 are really not separate individuals, and the whole 
 mass must be looked upon as one (Fig. 6). 
 
 Some embryos with tentacles are produced from 
 the ends of stems (Fig. 6, 6), and those which are 
 ciliated are derived from the thicker parts of the 
 stem (Fig. 6, a). 
 
 The endoplast is ribbon-like, and is much con- 
 torted in the stolon and band parts of the main stem, 
 and is continued as a band into the branchlets. 
 
 The next sub-order (the Actinaria) have the ten- 
 tacles simple or ray-like, as in the family Ephalotidse, 
 or represented by one or more retractile organs, 
 which resemble a proboscis with or without cirri. 
 The genus Ophryodendron (Fig. 15) is the type of the 
 last, and the species are very extraordinary looking 
 things. The animalcules may be solitary or in 
 a little group, and then one has a long proboscis, 
 and the others are more or less vermiform or flask-shaped, with a delicate tubular ending. The 
 prey is caught on the proboscis, and gradually withdrawn into the body. They inhabit salt water, 
 or fix on to the polyparies of Hyclrozoa, or on to Crustacea. The embryos are ciliated. 
 
 OKDER CILIATA. 
 
 In this order the animalcules are more or less covered with vibratile cilia, some of which may be 
 modified into setae, styles, and hooks or uncini. A well-developed oral and anal aperture is mostly present. 
 
 The example (Paramecium aurelia) already given of this order brings these important characters 
 before the mind. The order is divided into four sub-orders, of which the first is the Holotricha, 
 or the Animalcules, which are closely covered all over Math cilia, and usually furnished with 
 trichocysts. Paramecium is the example of the first family of the sub-order (Fig. 2). 
 
 The Prorodontid* are the second family, and they are ovate or cylindrical, and the oral aperture 
 is at one end or at the side. The canal (pharynx) leading from the mouth to the endoplasm is 
 bounded by rod-like teeth, which are well seen in the genus Prorodon (Fig. 10). 
 
 Fig. 15. A, Ol'HRYODENDUOX PEDICELLATOI ON A 
 
 PLUMULAKIA STEM (THE ELONGATE FORMS ARE THE 
 VERMIFORM BODIES) J B, MORE HIGHLY MAGNIFIED ; 
 C, O. MULTICAPITATUM. (After Saville Kent.) 
 
THE INFUSORIA CILIATA. 
 
 365 
 
 Fig. 16. EX- 
 
 CHELYS FAR- 
 CIMEX. 
 
 f)>, Contractile ve- 
 sicle n, nucleus 
 or endoplast. 
 
 The species Enchelys farcimen, which is found in stagnant water, and is from -^ gyth to 
 of an inch in length, has the oral cilia larger than the others, and the cuticle of the bag-shaped body 
 and changeable-shaped body is soft (Fig. 1C). 
 
 The flask-shaped, long-necked forms, with cilia over the whole body, and the 
 mouth at the end, constitute the family Trachelocercidse. Trachelocerca olor has a 
 body yi^th of an inch in length, and Jives in pond water. Its long neck and body 
 obliquely striated with cilia, the several contractile vesicles, and its double endoplast, 
 are all characteristic (Fig. 17). 
 
 The family Ichthyophthiriidse has the oral orifice in the midst of an adhesive disc, 
 and the cilia of the oral region are setose and radiate internally. The species of the 
 only enus is parasitic on trout and salmon and the loach. The contractile vesicles 
 in the sub-globose or ovate body are numerous, and its endoplast is curved. Length, 
 ^th of an inch (Fig. 14). 
 
 The family Colepidse contains ovate-shaped animalcules which have an indurated 
 cuticle, and the oral aperture terminal. Coleps hirtus is a good example, and it will be noticed 
 that the surface is furrowed, so as to present the appearance of being divided into numerous 
 equal quadrangular spaces. These are indurated, and the intervening furrows are soft and ciliated. 
 
 The mouth is at one end, and the cilia near it are larger than the others, 
 and the anus is at the opposite end. These Colepidse divide transversely, 
 and Coleps hirtus, which is from ^ thyth to -g^th of an inch long, has three 
 spinous processes at its nether end. It is a common species, living in 
 pond water amongst confervas. It is a voracious animalcule, and it may 
 be seen in numbers in the neighbourhood of any dead animal or vege- 
 table matters. These it takes in with its cilia, which form currents 
 mouthwards, and it may distend its body considerably (Fig. 13). 
 
 During the process of natural fission, the extremities retain their 
 usual aspect, but the newly-developed central area, where separation is to 
 occur, is smooth, and thus, after division, one part of each Coleps is 
 smooth, and the other like that of the parent. 
 
 There is a group of four families of these Holotricha which is charac- 
 terised by the presence of a portion of the cuticle or ectoplasm formed 
 into a flap, which may or may not vibrate. The Ophryoglenidse have the 
 oral aperture situated at the bottom of a distinct depression in the body, 
 within which is a vibratile flap or membrane. The genus Ophryoglena has the family character, and 
 the genus Trichoda resembles an Enchelys in shape, but the mouth is led to by an ovate furrow, 
 and from its inner wall starts a vibratile flap. This genus is common in putrid infusions 
 with the Enchelys already mentioned. A second family (the Pleuronemidse) .has the membrane 
 extending in front of the oral furrow in a hood-like manner, and it is not vibratile. The third family 
 (the Lembidse) has long, vigorously-swimming, worm-shaped animalcules, and the membrane 
 forms a long crest-like border to that furrowed part of the under surface of the body which extends 
 from the front, backwards, to the oral aperture. It has large cilia along its inner border. Lenibus 
 velifer has a long spike-shaped body, narrow in front, thicker behind, where the contractile vesicle is 
 seen, and the body is covered with long cilia. Beneath, in front, is the large membraniform 
 expansion like a fin, broadest in front. The front part of the body is elastic, and can change 
 its shape, and the hinder part is rounded. They increase by cross and longitudinal division 
 (Fig. 9). 
 
 The last family of the group has been discovered by Leidy, and its species are most extraordinary 
 looking things, and lead very remarkable lives. They are freely moving, but rarely swimming 
 animalcules, their movements being chiefly of a twisting and writhing kind. The shape is more or 
 less elongate and spindle-shaped, and the cuticle is entirely ciliate. Sometimes there are undulating 
 membranes on it. They occur as parasites within the intestine of the American White Ant (Termes 
 flavipetj). Leidy found some white ants which had their intestines, as seen through their translucent 
 abdomen, considerably distended with a brown substance, which consisted mainly of these parasites, 
 
 Fig. 17. A, ]!, THACHELO- 
 
 CEUCA OLOK. 
 C, cilia of the mouth 
 
3GG 
 
 NATURAL HISTORY. 
 
 Fig. 18. TKI- 
 CHONOMOBPHA 
 
 At; I u.s. (Letdy) 
 
 ranarum -- 
 
 decayed wood, and the filaments of one of the Algse. Trichonomorpha agilis (Fig. 18) has the cilia 
 various in length, forming three or four distinct sets, and one of them is very long. The body is 
 more or less separable into a smaller ovate head-like portion and a larger and inflated body. 
 The oral aperture is indistinct, and is a rounded pore at the summit of the head, whence there 
 passes backwards a tube to the endoplasm of the posterior part. There is a granular 
 nucleus in the centre, but no contractile vesicle has been observed. The movements 
 consist of an incessant retraction or shortening and bending to and fro of the head-like 
 anterior region, accompanied by the rapid waving and swelling outwards of the long 
 cilia. It is very possible that these animals may belong to another class of animals 
 altogether. 
 
 The last group of the Holotrichous Ciliata contains one family, the Opalinidse, 
 whose species are parasitic within the intestines of Amphibia and Invertebrata. The 
 genus Opalina is very characteristic, and its species are mouthless, free-swimming, and 
 they may be ovate or elongate in shape. The cilia cover the cuticle throughout, 
 and this is striated. There are no extraordinary organs of prehension, and the 
 spherical or oval endoplast is single in young individuals. It breaks up by repeated 
 divisions, as growth proceeds, into innumerable minute rounded bodies, each having 
 a clear peripheral zone and endoplastule. There is no contractile vesicle. Opalina 
 i to -A-th of an inch long, is found in the intestines and rectum of the common frog and 
 toad. Its body is usually ovate, flattened, evenly rounded posteriorly, and the anterior part 
 is bluntly pointed. The minute embryos contained in cysts (Fig. 19, G) are found in the rectum 
 and excreta of frogs in the early part of the year. They get into the water where tadpoles are 
 developing, and are eaten by them. The cyst has its wall broken or dissolved in the digestive canal 
 of the tadpole, and the embryo is set free. At this stage the young Opalina is long, 
 egg-shaped, covered with cilia, and has a large endoplast and a number of corpuscles in the 
 endoplasm (Fig. 19, 11). After a short interval, the body becomes longer, slightly curved in front, 
 and the endoplast becomes divided into two or four equal spheroidal portions (Fig. 19, i). After 
 a while the pointed end becomes 
 rounded, and the normal shape is 
 attained (Fig. 19, A). When fully 
 grown the animalcule begins to 
 increase in numbers by fission, 
 and the first division takes place 
 obliquely (Fig. 19, B), so that one in- 
 dividual has a pointed posterior end, 
 and the other a rounded-oif one. 
 The separated moieties subdivide 
 over and over again, first obliquely 
 and then transversely (Fig. 19, c, D), 
 until at last the pieces are not 
 more than -g^th to -f^th of an 
 inch in length. These are long, oval 
 in shape (Fig. 19, F), and soon 
 become languid in their movements, and contract to a spherical shape, diminishing in bulk and 
 becoming encysted. The endoplasts included in the animal at the encystment unite in one, after the 
 swallowing by the tadpole, and this one is carried out with the young free-swimmer. 
 
 Another genus of the Opaliiiidse is Anoplophrya, and 
 its species are parasitic within the intestinal organs of many 
 Invertebrata, The type is Anoplophrya prolifera (Fig. 20), 
 which is found in the intestinal cavities of various marine 
 Annelids on the Norwegian coast. It is mouthless, long, widest 
 in front, striated longitudinally, and ciliated along the striae. 
 The endoplast is in the axis, is long and sub-cylindrical, and the contractile vesicles are numerous, 
 
 Fig. 19. OPALINA RANARUM. (After Zeller and Englemann.) 
 Adult. B. Oblique division, c, Transverse fission. D. Fission. F, Last stage before 
 encystment. G, H, I, J, Stages of growth of young. 
 
 Fig. 20. AXOPLOPHRYA PROLIFERA. 
 (After Claparede and Lachmann.) 
 
THE LARGEST INFUSORIA. 
 
 367 
 
 Fig. 21. BUHSARIA 
 
 TRUNCATELLA. 
 
 (After Stein.) 
 
 ci; Contractile vesicle; , 
 cndoplast curved, 
 
 and in two long rows. These animalcules increase by several divisions across the body, and their 
 length is -., T -th of an inch. 
 
 SUB-ORDER HETEROTRICHA. 
 
 These Ciliata are free swimming or attached, naked or loricate, and the cilia form two widely 
 distinct systems ; those of the general surface being short, and those of the oral region large and like 
 cirri These oral cilia are either linear in their arrangement, or form more or 
 less spiral or circular series. The cortical layers are well developed, and some- 
 times contain parallel muscular fibrillae. 
 
 The largest Infusoria are amongst this sub-order, which may be divided into 
 a family, the Bursariadse (Fig. 21), which has the cilia near the mouth confined to 
 the left border of the mouth groove, and into six other families which have the 
 mouth cilia in a spiral or circular series round the aperture. The first family 
 of this second group has free-swimming animalcules, and the fringe of cilia 
 around the oral aperture is confined to the ventral surface, and the anal orifice 
 is behind and at the end. Spirostomum ambiguum is the type of the family, 
 and is one of the largest animalcules, measuring th to th of an inch in length, 
 and being visible to the naked eye, "gleaming," Saville Kent remarks, " like 
 golden threads in the sunlight " (Fig. 22). 
 
 When they are placed in clean water off the duckweed on whicli they 
 like to move, the body is long and filiform, has a tendency to twist itself and untwist, and the eye 
 is struck by the long contractile vesicle which occupies much of the hinder part of the body, 
 
 and by the endoplast, which is long and 
 moniliform. The slit for the mouth is 
 surrounded by cilia. 
 
 Another member of the family is 
 Condylostoma patens, found in sea water, 
 and -y-gth to T Vnd of an inch in length. 
 Its endoplast is moniliform and long, and 
 the anterior border of the body is rounded off, and flat in front, and the mouth groove is an angular 
 excavation occupying much of the ventral surface. There is an undulating membrane extending over 
 the whole length of the right side of the peristome border. The contractile vesicle is canal-like, and 
 breaks up into minor spaces (Fig. 12). 
 
 A most important family has the trumpet-shaped 
 animalcules in it, whicli are usually found adherent by 
 their narrow bases, and often freely swimming. The 
 broad trumpet opening of these Stentoridse is the 
 region around the mouth, and the left-hand extremity 
 is turned in spirally, forming a funnel-shaped groove 
 whicli leads to the mouth. The right-hand limb is 
 usually raised higher than the opposite one, and all the 
 cilia around the mouth are large and strong. The 
 cilia of the rest of the surface are small, and arranged 
 in regular longitudinal rows, and there are occasional 
 setae. The endoplast is canal- like, and the contractile 
 vesicle is an anterior circular dilatation, which gives off 
 an annular branch that underlies the circumference of 
 the peristome. 
 
 Stentor polymorphic (Fig. 23) is a large form, and 
 the colour is produced by the presence of rich green, 
 chlorophyll gi-anules. Its endoplast is moniliform, and 
 the whole trumpet is ^th of an inch long. It lives in 
 groups, and the stems of all are immersed in a mucus which they secrete and hold on by. When 
 swimming the shape is altered, and may be pear-shaped or top- shaped, and they fix them- 
 
 Fig. 22. SPIROSTOMUM AMBIGUUM. 
 cr, contractile vesicle. 
 
 (After Stein.) 
 
 Fig. 23. STEXTOK POLYMORrHUS. 
 
368 
 
 NATURAL HISTORY. 
 
 selves at pleasure. They increase in numbers by oblique fission, and a rudimentary mouth 
 fringe appears, and only in the part of the body which will require it after division. They live 
 in standing water among living and dead vegetation. One of the genus has blue colouring matter, 
 and another, in addition to its green chlorophyll, has spots of a brilliant scarlet, and a third is 
 black. The species of the genus Folliculina secretes a lorica, and the peristome opening occupies the 
 end of the projecting part of the animalcule (Fig. 24). Tintinnus lagenula is a type of a family of 
 this sub-order (Fig. 7). 
 
 SUB-ORDER PERITRICHA. 
 
 These Ciliata have the body smooth, except where there is a circular or spiral wreath of cilia in 
 front. Sometimes there is a second encircling wreath which may be at 
 the posterior part of the body, or at the middle. When the anterior 
 circlet of cilia assumes a spiral form the right limb of the part around 
 the mouth is mostly band-like and long. These animalcules may be 
 free swimming or attached in colonies, and in this case often forming 
 branching growths. They multiply by transverse and longitudinal 
 fission, and by conjugation. 
 
 This very important sub-order is well divided into those families 
 which are free swimming, and those which are sedentary or attached. 
 
 There are seven families of free swimmers, and in the first, con- 
 taining the genus Torquatella, the cilia around the mouth are replaced 
 by a vibratile collar. The second family has the animalcules 
 protected by a silicious covering or lorica, and the third has no 
 lorica, and there are retractile tentacules with the fringe of cilia in 
 the front. 
 
 Halteria grandinella (Fig. 25) is the type of the fourth family, 
 and is a free-swimming globular animalcule, and it has the oral aperture 
 at one end, and associated with a spiral or sub-circular wreath of 
 large en-rate cilia. There is a zone of long hair-like setae around the 
 
 body equatorially, and they enable the creature to jump in a most extraordinary manner. They roll 
 
 themselves about, and suddenly leap backwards on to one side. There is a contractile vesicle and 
 
 a spherical endoplast. The length is from ^-J-^th to y-J^th of an inch, and it inhabits pond water. 
 Another family has the animalcules pear-shaped ; the mouth is lateral, and there is a fringe of 
 
 cilia around the body equatorially. Urocentrum turbo (Fig. 26) is the example, an:l the zones of cilia 
 
 are in front, and equatorially, there being a terminal style, 
 
 which is flexible, and enables the animalcule to adhere. 
 
 The endoplast and contractile vesicle are very visible. It 
 
 rotates like a top in the water, and moves forwards and 
 
 backwards, and fixes itself, and spins backwards and 
 
 forwards, so as to twist and untwist its stalk. The 
 
 contractile vesicle has two or four sinuses, and the 
 
 contraction expels the water visibly externally. They 
 
 increase by transverse division. 
 
 In the family Urceolaridse the wreath of cilia is 
 
 near the adhesive disc-like posterior end, and the seventh 
 
 family is peculiarised by its terminal setae, and a spinal 
 
 adoral wreath of cilia. 
 
 The family which contains the genus Dictyocysta is characterised by the possession of a beautiful 
 
 helmet-shaped or bell-shaped silicious lorica, which is usually perforated so as to resemble a fine lace- 
 work. The species are from salt waters, are free swimmers in the Mediterranean and south-west 
 
 coast of England. In their tests they closely resemble Polycistinse. 
 
 The family Vorticellidse comprehends the Peritricha which are fixed during the greater part 
 
 of their lives, and which are only temporarily free swimming. These are the " Bell Animalcules " 
 
 Fig. 24. FOLLICULINA AMPULLA. 
 
 (Modified after Stein.) 
 
 A, Protruding from, and B, contracted in 
 lorica; c, Spirorbis shell with animal- 
 cules attached. 
 
 Fig. 25. HALTERIA GRANDIXELLA. 
 
 , Ventral, B, lateral, aspect; cv.contractile vesicle; n, nucleus. 
 
THE "BELL" ANIMALCULES. 
 
 369 
 
 Fig. 26. A, B, UROCENTRUM 
 TURHO ; C, TRANSVERSE 
 FISSION. 
 
 which form colonies, and the commonest of which have their stalks contracting, often in a corkscrew 
 shape, the end of the bell being provided with a circle of long active cilia. Occasionally they may 
 be seen freely swimming, and then there is a second circlet of cilia at the tail end ; but they soon 
 settle down, become attached, and grow a stalk, the lower circlet of cilia disappearing. Very often 
 the o-roup of these stalked Vorticellidse are so large that they are visible to the naked eye, and hence 
 they were amongst the first animalcule described. There are numerous genera, ai-ranged in sub- 
 families, and some have no stalk and others have it, and they may be 
 solitary or social, arranged in branching groups on a common stem or im- 
 mersed in mucus. The animalcules are highly contractile, and vary in 
 shape from that of a long egg to sub-cylindrical, or a long or broad bell 
 shape (Fig. 11). The free end of the bell consists of an outer raised border, 
 sometimes but not always ciliated, and this closes the opening like a 
 sphincter when the animalcule shuts up. As it reopens this peristome is 
 seen to environ a spiral membrane with a circle of cilia on its free surface, 
 and this projects beyond the peristome and the cilia produce very forcible 
 currents in the water. On one side the circle is incomplete, and leads to 
 a furrow which is often prolonged backwards on the body to a canal-like 
 opening to the mouth. The movements of the cilia cause the particles of 
 food to take the direction of this furrow, which has often a long solitary 
 
 cilium at its free end. The spiral part, or disc, can be protruded or retracted. The endoplast is 
 band -like and lai-ge, and the contractile vesicle is single, spherical, and is placed close to the anal 
 aperture, which is distinct near the furrow. The stalk, when it exists in its highest degree of 
 perfection, has an outer cuticle continuous with that cf the body, and an inner spiral tissue more 
 or less longitudinally fibrous, which is continuous with the myophan layer of the hinder part of 
 the bell. Contraction 'produces spiral winding of the stem in some species, and a slow unwinding- 
 happens subsequently. 
 
 The animalcules rarely divide by transverse and usually by longitudinal fission, which takes 
 place through the endoplast and contractile vesicle. The offshoot grows a circle of cilia close to the 
 
 stalk, which does not divide, and after a while it escapes 
 as a free swimmei'. In some species there is a free- 
 swimming and small animalcule, which finally settles 
 on the side of one of the larger fixed individuals, and 
 either penetration occurs or the contents of the smaller 
 pass into the larger. The endoplast subsequently 
 develops a host of germs, which escape and become 
 like the parents with growth. 
 
 In the sub-family Vorticellina the animalcules are 
 naked, long, without a stem, and are sessile on sub- 
 stances ; some have a distinct sucker, by which they 
 cling on, mostly to moving invertebrata and sometimes 
 to weeds in fresh water. One of the genera (Spirochona) 
 has solitary individuals, and the peristome is developed 
 into a spiral funnel, and in Stylochona there is a rigid 
 pedicle or stem instead of a sucker at the tail end. Then 
 there is a genus with all the characters of the genus 
 Vorticella, but the stem is rigid and uncon tractile, and 
 the animals are solitary ; and in the genus Pyxiclium the 
 solitary animalcules have a rigid stem and a ciliary 
 disc projecting beyond the peristome. These forms 
 lead up to Vorticella as a genus, which is the type 
 
 of the family. Vorticella nebulifera (Fig. 27) is common in ponds attached to duckweed or 
 other water plants, and is a very beautiful object under the microscope. The bell-shaped 
 body of each individual is about -gtTo tu of an inch in length, and is attached to a long 
 
 Fig. 27. VORTICELLA NEBULIFERA. 
 
 cv, Contractile vesicle. 
 
 85 
 
370 
 
 NATURAL HISTORY. 
 
 flexible stem, which is for a while extended to the utmost, the cilia of the disc and peristome being 
 in full action. Suddenly the stem contracts, becomes spiral, and the body closes slightly and bends 
 on its stalk. Then the oral end opens, the cilia move again, and the stalk is drawn out to the 
 
 utmost. This goes on very irregularly in a colony 
 of a score or more of individuals, so that whilst 
 some are contracted others are in full play. The 
 currents in the water, produced by the ciliary fringes, 
 are considerable and move much disintegrated 
 matter into the oral grooves. The phenomena of 
 fission and conjugation may be seen in the same 
 colony at the same time, and every now and then a 
 bud moves off by means of its hinder circle of cilia. 
 In the genus Carchesium, which belongs to 
 this group, a host of animalcules are on branchlets 
 springing from a common stem. Usually the bell- 
 shaped bodies are on one side of their branchlet, 
 and each one has a stem continuous with the branch 
 and main stem. A muscular tissue resembling 
 that of Vorticella is in the stem and its prolonga- 
 tions, but it is discontinuous, so that each body can 
 contract without the others, and each branchlet 
 can do the same irrespectively of others, and the 
 whole may contract with the primary stem and 
 form a small globular mulberry -looking mass. 
 
 The species live in fresh and sometimes in 
 salt water, and the whole colony originates in the 
 fission of one individual and its stalk, and is fully 
 developed by the successive longitudinal fissions of 
 body after body (Fig. 28, D). 
 
 The semis Zoothamnium has the animalcules 
 
 Fig. 28. A, ZOOTKAMXIt'M XIVEUM (SnviUe Kent) ', B, 
 SINGLE ANIMALCVLE, MOKE HIGHLY MAGNIFIED ; C, 
 
 EPISTYLIS UMBILICATA; r>, BRANCHLET OF CARCHESIUM 
 
 POLYPINUM ; E, AX EPISTYLIS GROWING ON A CYCLOPS. 
 
 like those of Vorticella, but often dissimilar in 
 shape and of two sizes, and they are placed at the 
 end of a branching, highly contractile stem. The 
 internal muscle of the stem is continuous throughout. This is not spiral in its construction, so that 
 the stem never forms a spiral during its contraction. In Zoothamnium niveum, 
 which is a salt-water form, there are spherical animalcules of large size near the 
 bases of the primary branches, and the smaller ones at the ends of branchlets are 
 long bell-shaped (Fig. 28, A, B). 
 
 Another genus, Epistylis, with its animalcules closely resembling Vorticella, 
 has them attached in numbers to a rigid, uncontractible, 
 branching, tree-like stem, and the bodies are of the same 
 size throughout. Epistylis fiavicans forms slimy encrusta- 
 tions on water plants and on the sides of aquaria. Many 
 species settle on small Crustacea (Fig. 28, c, E). 
 
 The next sub-family includes animalcules which excrete 
 hard sheaths as loricre and live within them. The genus 
 Pyxicola, whose species live for the most part in salt water, 
 has an erect lorica or a stem of attachment, and a horny 
 plate on the body beneath the border of the peristome. 
 This closes in the top of the lorica when the animal retreats. 
 They inhabit fresh and brackish water (Fig. 29). 
 The last sub-family, the Ophrydiiire, contains Vorticella-like animalcules which excrete and 
 inhabit a soft mucilaginous sheath or mass which may contain many. 
 
 Fig. 30. OPHEYDIUM EICH 
 
 HOENII. (After Saville Kent.) 
 a, 0. sessile, natural siz?. 
 
 Fig. 29.^1 
 
 PYXIDIFOEMIS. 
 
HYrOTRICHOUS INFUSORIA. 
 
 371 
 
 31. CHLAMYDODON 
 MNEMOSYNE. 
 
 A, Under, B, side view. 
 
 Ophrydi/u/nt Eichhornii (Fig. 30) is an example, and it forms attached gelatinous masses in which 
 are numerous individuals, each with its slender pedicle. The body is long and narrow, and the 
 whole is very elastic. They live in fresh water, attached to Anacharis, and about a hundred may 
 be in a mass measuring ^th of an inch. They increase by transverse as well as by longitudinal 
 
 fission. 
 
 SUB-ORDER HYrOTRlCHA. 
 
 These animalcules are free swimming, and the locomotive cilia are confined to the inferior or 
 ventral surface, and are often modified into setae and hooks. The superior surface 
 is either smooth, or has some immobile setae on it. The mouth and anus are ventral. 
 Saville Kent subdivides this group into six families and forty-two genera. 
 Chlamydodon mnemosyne is the type of one family, and it has a short, kidney- 
 shaped body, the front being wide and the dorsal surface convex, and the 
 ventral having a striated border. The cilia are the most conspicuous anteriorly, 
 and they project as a fringe. The oral aperture has a bundle of rods in its mem- 
 brane. The endoplast is single and ovate, and there are many contractile vesicles. 
 It inhabits salt water (Fig. 31). 
 
 Another family, the Dysteriidae, mostly inhabit salt water, and these free 
 swimmers are mostly provided with a lorica either single or made up of two joined or detached 
 valves like a small crustacean. The cilia are on the lower surface and the 
 oral aperture leads to a canal, or pharynx, with a horny tube, or rods. The 
 ' animalcules have a conspicuous tail-like style, or a group of setae. 
 
 Dysteria armata, a salt-water form, Tr^th to -g^th of an inch in length, 
 is remarkable for the anatomy of the pharynx. The oral fossa has a curved 
 rod which terminates in fork-like teeth, and which is lost in the walls of 
 the fossa. Then comes the armature of the pharynx, which consists of two 
 portions an anterior rounded mass in opposition with a much elongated 
 styliform posterior portion. These animalcules live in swarms among the 
 confervoid Algae which coat the shells of limpets and periwinkles (Fig. 32). 
 
 The family Peritromidae has the ventral surface finely ciliate, and tluire 
 Fig. 32. DYSTEIUA is a curve of powerful cirri around or near 
 AKMATA. (After Huxley.) the mouth, and the pharynx is unarmed. 
 A, Left side ; B. a, pharyngeal A1 ,, ., , . . , . , 
 
 apparatus. A host or flexible or persistent m shape 
 
 animalcules, with front, ventral, and rear 
 
 styles, and hooks and setae at the margin, belong to the Oxytri- 
 chidae. The common Stylonychia mytilus is an admirable ex- 
 ample. It has a hard covering, or lorica, and the neighbourhood 
 of the mouth has a great curve of long cilia on an undulating 
 membrane. There are usually eight styles in front, five claw-like 
 hooks on the ventral surface, and five straight anal styles. The 
 marginal setae form a border, and there are three long tail-like setae. 
 There are two endoplasts, sometimes divided, and a contractile 
 vesicle. It inhabits fresh water, and the largest are T Vnd of an inch 
 long (Fig. 8). 
 
 Another species (Stichotricha remex, Fig. 33) has the cilia of 
 the apex of the peristomial border very long, and the body is A, Animals in tubes ; B, free animalcule ; c.dia- 
 
 J * gram of Schizosiphon. 
 
 lanceolate, and inhabits a slender, brown tube, 
 
 three or four times as long as the body, which projects from it with a twist. 
 
 Closely allied to these dwellers in separate tubes is a species (Schizosiphon 
 socialis) which forms colonies that build up a branching tube. Another of this 
 great family is Uroleptus piscis, and it is remarkable for its attenuated end, two 
 endoplasts, and great curved ciliated peristome. 
 
 A family of the Hypotricha has no setae along the margin, or they are rudi- 
 mentary, but there is a lorica, and there are ventral and anal styles, or else hooks. In Euplotes 
 
 Fig. 34. -ETJPLOTES 
 
 CHARON. 
 
372 
 
 NATURAL HISTORY. 
 
 charon the dorsal surface of the body is ribbed, as it were, and there are seven frontal and three 
 ventral styles, besides five posterior strong setre (Fig. 34). 
 
 ORDER CILIO-FLAGELLATA. 
 
 The animalcules of this order are readily distinguished by their bodies being more or less 
 ciliated, and by their having a long lash-like flagellum. The mouth is usually distinct. Saville Kent 
 divides them into four families and sixteen genera, and the individuals are occasionally very numerous, 
 producing the phosphorescent condition of the sea, and discolouring fresh and salt water. Most of 
 the Cilio-flagellata, a type of which has already been noticed (pp. 356-7), are small, -g^th of an inch 
 being the greatest length, but amongst the genus Ceratium there are some large forms, some reaching 
 Y^th of an inch in length. They are found in fresh and in salt water ; and, so far as is known, none 
 are parasitic or sedentary ; but during one of the reproductive phases encystment occurs, and a 
 period of quiescence precedes the escape of the young. They are active swimmers as a rule, the 
 lash-like flagellum (in rare instances there are two) enabling rapid and irregular motion easy, and 
 the cilia produce ordinary movement. Fission occurs, but the reproductive phenomena have not 
 been observed satisfactorily. Some of the Cilio-flagellata are naked, and others have a shell, or 
 horny cuirass, which may be smooth or ornamented, and often prolonged into horn-like processes. 
 Some of these loricse have been preserved in the strata of the chalk, and are referred to the genus 
 Ceratium. The general character of the group having been given already, it is only necessary to 
 observe that the family Peridinidse contains ten genera. In all there is a distinct ciliary girdle, and 
 one flagellum. In a doubtful genus there are two of these organs. In some of the genera the ciliary 
 girdle is central, in others eccentric, and in one it is terminal. Some genera have a cuirass, and many 
 others are naked. Melodinium, already noticed (p. 356), is an example of a naked, and Ceratium 
 of a cuirassed and honied genus. Peridinium has no horn-like processes, and the cuirass is facetted 
 
 (Fig. 4, A-H). 
 
 The second family* has one vibratile flagellum, and one which is trailed, and the body changes 
 in shape, like Amoeba ; and the third familyt has the body clothed with long setose cilia, and a 
 terminal flagellum, the body shape being persistent. A fourth family has a wreath-like crest or 
 collar of cilia, and in the midst a flagellum, which may or may not be retractile ; J and the last 
 family, which links the order with that of the Ciliata, has a more or less perfect ciliary covering, 
 and a flagellum. The colours differ, and there may or may not be a red spot in these families. 
 Yellow, light-brown, green, pink, reddish-brown, vermilion, are common colours ; and usually the 
 endoplasm is transparent, and holds coloured matters in suspension. Peridinium splendor-marls 
 of Naples is highly phosphorescent, and P. sanguineum, of salt-water pools and the sea-shore of 
 India, is green when young, and with growth a number of oil globules is secreted within, and the 
 green colour disappears, and a bright red tint comes on, just before encystment. The red colour of 
 
 patches of the sea is due to this form, in many 
 instances, and it is noteworthy that the 
 presence of these animalcules renders water 
 c ^ .x-k. very disagreeable. 
 
 Fig. 35. MONAS DALLIXGERI. (Saville Kent. ) 
 
 A, B, Adult : c, about to encyst; D, K, p, eneystment formation of spores which 
 are liberated as monads; G, H, conjugation : i, cnrygtment from conjugation; 
 j, bursting of and liberation of spores ismall). 
 
 ORDER FLAGELLATA. 
 
 These animalcules, generally very minute, 
 have one or more long slender flagella ; there 
 are in some instances pseudopodia. The 
 mouth may be doubtfully present, and food 
 may be taken in at one' spot, or anywhere. 
 One or more contractile vesicles are almost invariably present. They increase by fission, or In- 
 breaking up of the endoplasm in the encysted state. 
 
 This definition explains how difficult it is to limit the lower Flagellata. It is possible that many 
 of the so-called Flagellata are stages of plants, and indeed it seems impossible to draw a hard and 
 
 * ffeteromastigidce (Fig. 4, K). t MaUomonadidce (Fig. 4, L). J Stephanomonadidai (Fig. 4, i). 
 
 Trickoncmidcc (Fig. 4, j). 
 
FLAGELLATE INFUSORIA. 
 
 373 
 
 fast line where the animal and vegetable kingdoms branch off. Saville Kent has paid much attention 
 to the order, and his descriptions and classification are excellent. 
 
 The Flagellata may be divided into three sub-orders : in the first there is no defined mouth, 
 and the food may be taken in by any part of the body, and in the second the food is received in the 
 
 Fig. 36. A, CLADONEMA LAXA. (After Saville Kent.) B, ANIMALCVLE DIVIDING J C, ANTHOPHYSA VEGETANS, SWIMMING 
 
 CLUSTER; D, ANTHOPHYSA VEGETANS, SIIOKT BRANCHING COLONY; E, SPOROCYST LIBERATING <;ERMS. 
 
 anterior region. A true opening for food exists in the third, which have a non-ciliated body with 
 
 a flagellum. The sections of the first sub-order are the Trypanosomata, membranous organisms found 
 
 in the blood of frogs and toads ; the Rhizo- 
 
 flagellata, which have amcebiform bodies and 
 
 a flagellum ; the Radio-flagellata, with or 
 
 without a lorica, having a flagellum, and 
 
 ray -like pseudopodia ; and the Flagellata- 
 
 Pantostomata proper, which have a flagellum 
 
 and the food incepted anywhere. A host of 
 
 genera belong to this sub-order and Monas 
 
 may be represented by 
 
 Monas Dallingeri, -^^th of an inch 
 in length. It has one flagellum, which is 
 flexible when young, and rigid towards the 
 base in old specimens (Fig. 35). 
 
 Cercomonas has a caudal filament besides 
 a flagellum (Cercomonas typica, Fig. 3). 
 
 The genus Cladonema, as the name im- 
 plies, has a branching form, and the ovate 
 bodies are attached to thread-like pedicles. 
 There are two flagella (Fig. 36, A, B). 
 
 Anthophysa, a genus belonging to the 
 same family, has small individuals -^V^th 
 to ^oV^th of an inch in length, and is in the 
 form of clusters of fifty or sixty bodies at 
 the ends of branching horny pedicles. These 
 have contractile vesicles (Fig. 36, c, D). 
 
 Shipidodendron splendidum (Fig. 37) 
 is in masses, y^th of an inch long, and has 
 its bodies with two flagella. These are in a 
 
 Fig. 37. RHIPIDODENTRON SPLENDIDUM. 
 
 branching maSS, like a fan in shape. A , colony ; B, animalcule bifurcating ; c. isolated mouad. 
 
374 
 
 NATURAL HISTORY. 
 
 The second sub-order comprehends Saville Kent's division of the collared monads (Choano-flayellata}, 
 with individuals varying from TI7 Vo th to ^oVo th of an inch in length, and some of which resemble the 
 collared cells of sponges. It consists of three families. In the first the animalcules are naked, and 
 either attached or free ; the genera Monosiga, Codosiga, and Astrosiga are examples (Plate 72, 
 Figs. 1 8). The forms of the second have a lorica, which may be solitary, as in Salpingaeca and 
 Lagenseca, and united in Polyneeca (Plate 72, Figs. 9 18). 
 
 In the sub-order of the Flagellata, with a definite region for inception of food (Eustomata), the 
 most interesting examples are the genera Noctiluca and Euglena. The first is one of the greatest 
 producers of the phosphorescence of the sea. 
 
 Noctiluca miliaris, from J^th to ^th of an inch in diameter, is peach -shaped, and has a distinct 
 meridional groove to its hyaline body. The mouth fossa is at one end of the groove, and has on one side a 
 
 Fig. 38. A, NOCTILUCA MILIARIS; B, SAME WITH BUDS (from Photograph after Broofo) ; 
 
 C, IK SECTION. (After Huxley.) 
 n, nucleus; /, flagellum; t, tentacle; d, denticle; an. anus. 
 
 hard projecting ridge, close to one end of which arises the flagellum. Close by arises a tentacle about as 
 long as the body, and there is a rod-like induration of the cuticle, extending in a straight line from the 
 aboral extremity of the gi'oove. The endoplast is oval. They exist in countless multitudes, and their 
 greenish-silvery light is produced just underneath the ciiticle in irregular flashes. They increase by 
 transverse fission, accompanied by encystment and loss of the flagellum and tentacle. 'Under certain 
 circumstances, the endoplast breaks up, and the protoplasmic contents of the cyst collect in one spot 
 and form by division into many minute nodular masses. These cause the cuticle to rise, and finally 
 they penetrate it and develop flagella. They become detached and swim as germs (Fig. 38). 
 
 Conjugation is also observed. The Noctilucse live on minute floating Algae, which may be seen 
 amongst the vacuoles of the irregular endoplasm. 
 
 CLASSIFICATION. CLASS INFUSORIA. 
 
 ORDER TENTACULIFEIIA 
 
 ClLIATA 
 
 ClLIO-rLAGELLATA. 
 
 FLAGELLATA . 
 
 Holotricha. 
 Heterotricha. 
 Peritrieha. 
 Hypotricha. 
 
 ( Pantostomata. 
 < Choano-flagellata. 
 ( Eustomata. 
 
 The writings of Claparede and Lachmann, Stein and Huxley, have been used by the author ; 
 but his greatest obligations are to Mr. Saville Kent, whose excellent Manual of the Infusoria has 
 been quoted largely, and often word for word, 
 
 P. MARTIX DUNCAN. 
 
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