LIBRARY OF THE UNIVERSITY OF CALIFORNIA BIOLOGY LIBRAE Ctass 9 ZOOLOGY; Systematic: TUB GENERAL STRUCTURE, HABITS, INSTINCTS, AND USES OF THE PRINCIPAL FAMILIES OF TFIE A3MAL KINGDOM; AS WELL A8 OF THE CHIEF FORMS OF FOSSIL REMAINS. WILLIAM B. CARPENTER, M.D., F.R.S., LECTURER OX NATURAL IIISTOUY AND COMPARATIVE ANATOMY AT ST. THOMAS'S HOSPITAL. A NEW EDITION, THOROUGHLY REVISED, BY W. S. DALLAS, F.L.S. &o, 1 c • IN TWO VOLUMES VOL. II. ' LONDON: BELL & DALDY, G, YOKE STKEET, COVENT GARDEN, AND 186, FLEET STIIEKT. 1867. \J1 BIO R G LONDON: MHNTED BT W. CI.OWKS AND *,XS, srASIK«>Ul» OTRECT AXP OHARJNG CROSS. CONTENTS OF YOL. II. CHAPTER VII. PAGE OF THE CLASS OF FISHES ...... 1 ORDER I.— SELACHU . . . . .29 ORDER II. — GANOIDEI .... 39 ORDER III. — TELEOSTEI . . . . .43 A. — PLECTOGNATHI . 4i> B. — LOPHOBRANCHII . . . . .47 C. — ACANTHOPTERI .... 48 D. — PHA.RYNGOGNATHI . . . .62 E. — ANACANTHINI .... 65 F.— PHYSOSTOMI . . . . .68 ORDER IV.— CYCLOSTOMI .... 76 ORDER V. — LEPTOCARDI . . . . .78 CHAPTER VIII. GKEITEEAL CHAEACTEES OF ABTIOTTLATED ANIMALS . *75 CHAPTER IX. OF THE CLASS OF INSECTS 84 SUB-CLASS A. — METABOLA. ORDER I. — COLEOPTERA . . . . . 117 ORDER II. — ORTHOPTERA .... 141 , first dorsal ; d8, second dorsal ; c, caudal; a, anal; o, opening of gill-covers. The anterior members, which correspond with the arms of Man and the wings of Birds, are fixed on each side of the trunk, immediately behind the head, and are called pec- toral fins. The abdo- minal members are less separated from each other, and are generally found on the lower side of the body ; they may be situated more or less forwards or backwards, from the under part of the throat to the com- mencement of the tail ; these are called ventral fins. The single fins occupy, as we have already said, the central line of the body ; and are divided into dorsal fins, anal fins, and caudal fins, according as they are placed along the back, under the tail, or at its extremity. They have all very nearly the same structure, and consist almost always of a fold of skin, supported by bony or cartilaginous rays ; very nearly in the same manner as tho wings of bats and dragons are sustained by the fingers or by the ribs, of the animals. 537. On the external surface of the body, large openings are seen on each side ; which are placed immediately behind the head, and which serve as an outlet for the water that has passed through the gills. In general there is only one on each side ; and its anterior edge is moveable, and resembles a flap or valve. 538. The skin is sometimes almost entirely bare, but it is generally covered with scales. Occasionally these scales have the appearance of coarse grains, at other times they exist as large tubercles or plates of considerable thickness; but in general they present the aspect of very thin laminae or plates, arranged in the manner of tiles upon a roof, and held together in the folds of the skin. We may compare them to our nails ; but they contain a much larger quantity of calcareous salts. The SKELETON OF FISHES. 3 colours with which these animals are adorned, astonish us by their variety and splendour. The silvery matter, which frequently gives to them so beautiful a metallic splendour, is secreted by the skin, and is composed of a number of small polished laminae. — Along each side of the body in most Fishes there is a single series of peculiar scales, eacli bearing a minute tube. This series of scales is commonly known as the lateral line, and its differences often furnish valuable characters for the determination of the genera and species of Fishes. The object of this curious arrangement is not yet well made out. The little tubes open into a canal which runs along beneath the lateral line ; this has generally been regarded as a glandular organ furnishing that slimy secretion with which the skins of all Fishes are covered. By modern Zoologists, how- ever, this slimy matter is considered to represent the outer coat of the epidermis ; and it appears that the lateral canals communi- cate with a curious arrangement of tubes situated in the head, and furnished with nerves, the use of which has not been ascertained. 539. The skeleton of Fishes is usually bony ; but in many cases, as in the Ray and the Shark, it remains permanentl}' in a fibre-cartilaginous or cartilaginous state ; and in some this frame- work possesses even still less solidity, and remains perfectly mem- branous : certain Lampreys are in this condition, and thus form a transition between the Vertebrated and Invertebrated animals. FIG. 346.— SKELETON OF THE PERCH. — The bones never have any medullary canal ; and the cartilage which constitutes their foundation is not the same, as that of the B 2 4 BONES OF THE HEAD OF FISHES. Mammalia and Birds ; for, when boiled in water, it does not give out any gelatine. 540. The skeleton is composed of the head, to which is joined a highly-developed apparatus which is subservient to respiration ; of the trunk ; and of the members. — The structure of the head is very complicated. At first is seen a central or median portion, composed of a great number of bones united together by sutures, and forming a kind of immoveable keel, with which are connected the bones of the jaw, the cheeks, &c. This median portion, of which the general form is very nearly that of a three-sided pyra- mid, with its summit directed forwards, has at its back part the cavity of the cranium, containing the brain. Its sides are hollowed out to form the orbital cavities, or; and in front are seen the aper- tures belonging to the olfactory apparatus, n; and a kind of large knob, formed by the vomer, and serving to support the upper jaw. (Fig. 347.) We may distinguish the bones corresponding with the occipital, the temporal, the sphenoid, the parietal, the frontal, the ethmoid, and the vomer ; but most of these are composed of several --\— op t p io FIG. 347. — Bones of the head of Pike ; c, cranium ; or, orbit ; n, nasul cavities ; im, intermaxillary bone ; m, superior maxillary bone ; t, lateral partition, separating gills from mouth ; p, to, op, bones of operculum, or gill-cover. pieces, which never acquire the union that takes place at an early period among the Mammalia and Birds.— At the front of this cranial portion of the head is placed the upper jaw, which is sometimes immoveably fixed, but generally preserves great freedom of motion ; we may distinguish in it on each side an intermaxillary bone, placed near the median line, and a maxillary bone, which extends side- ways, and which is moveable upon the first. 541. A chain of small bony pieces extends on each side, from BONES OP THE HEAD OP FltfUES. 6 the anterior angle of the orbital cavity to its posterior angle, and thus completes the circle of the orbit. Further inwards is seen also on each side a kind of vertical partition, (Fig. 347 2,) which is suspended to the skull, and which separates the orbits and the cheeks from the month. It is formed by bones cor- responding with the palatine, pterygoid, and tympanic bones of i I co ca cm h r b I F,0. 348 Bones of the head of the Perch, after the removal of the jaws, lateral par- tition, and operculum, on one side, to show the interior of the mouth, and the hyoid apparatus; c, cranium; or, orbit; v, vomer (armed with teeth) ; im, superior maxil. lary ; dp, teeth implanted on the palatine arch ; mi, lower jaw ; I, lingual bone ; b, lateral branches of the hyoid apparatus ; s, process for the attachment of these to the lateral partition ; r, r, branchio-stegal rays ; a, branchial arches ; ph, superior pharyn- geal bones ; ar, articular surface by which the lateral partition is attached ; o to ft, bony framework supporting the pectoral Gn,p ; o and o', scapula divided into two pieces ; h, humerus ; ab, bono of the fore-arm ; ca, bone of the carpus ; co, coracoid bone. the. higher Vertebrata. At its under part it gives attachment to the lower jaw ; and behind it is prolonged in such a manner, as to form a kind of rnoveable flap, which protects the respiratory apparatus, and is termed the operculum or gill-cover. The lower-jaw is formed of three pieces on each side. Within the lateral partitions just described, and lying at the bottom of the mouth, is found a framework of very complicated structure, 6 BONES OF THE HEAD OF FISHES. which serves for the support and protection of the gills, and which appears to resemble the hyoid bone of higher animals enormously developed. (Fig. 348.) The bone of the tongue, /, is continued backwards by a series of pieces on the central line ; and is articulated on each side with a lateral branch of great length and thickness, which, by its opposite extremity, is suspended (as it were) to the internal face of the before- mentioned partition. These lateral branches, formed of several bones, carry at their lower border a series of flattened rays, r, r, curved backwards, which unite with the opercular bones to complete the walls of the branchial cavities, and which are known under the name of branchio-stegal rays. Behind these branches we meet with four pairs of bony arches, a, passing off from the central portion of the hyoid apparatus. These are first directed backwards ; they then curve upwards and inwards, and are at last fixed to the base of the cranium by a series of small bones, ph, termed the superior pharyngeal. These arches support the gills, and are thence called branchial arches. Lastly, at the entrance of the resophagus, are seen two inferior pharyngeal bones ; which are usually so placed, as to apply themselves against the superior pharyngeal just mentioned. 542. Such is generally the complicated structure of the bony head of Fishes. Some anomalies, however, are occasionally ob- served; thus amongst the Sword-fishes and some other allied species of Tunny, the upper jaw is prolonged, so as to constitute a kind of beak, like a spit or the blade of a sword : which serves these fish as a TIG. 349.— SWORD-FISH. powerful weapon to attack the larg- est marine animals. We shall not dwell here on the comparison of the different pieces of which the head of Fishes is composed, with the bones of the head of the Mammalia ; as some points connected with this subject must still be regarded as uncertain ; and the de- tails necessary to render it intelligible would lead us too far. 543. The vertebral column, which immediately follows the head, only presents two distinct portions, the one dorsal, the BONES OP THE TRUNK OF FISHES. 7 other caudal (Fig. 346) ; for here there is neither neck nor sacrum. The body of the vertebrae has a peculiar form, being hollowed before and behind into a conical cavity ; these two cavities sometimes unite in such a manner, as to form a con- tinuous passage ; and the double conical cavity, which is formed when two vertebrae are placed together, is filled with a soft sub- stance. The ring destined for the passage of the spinal marrow is surmounted by a spinous process ; and on each side there is generally seen a transverse process more or less distinct, which, beneath the abdominal cavity, extends outwards, and is usually united with the corresponding rib ; but which, in the caudal portion of the column, is directed downwards, and often forms with that of the opposite side a ring, from the lower part of which arises a long spinous process, similar to that which is situated on the dorsal side of the vertebrae. — The ribs are some- times entirely absent ; at other times they surround the abdo- men, and amongst a small number of Fishes they are joined to a series of single bones, which ought to be considered a sternum. They often bear one or two pointed projections, which are directed outwards, and penetrate into the muscles. There are also, sometimes, similar processes, which spring from the bodies of the vertebrae ; and it is thus that, in some tribes, such as amongst the Herrings, the small bones of Fishes become very numerous. Lastly, we find on the central line of the body a number of bones, termed interspinous (Fig. 350), which are usually applied against the extremities of the spinous processes of the vertebrae, and which articulate at their opposite ends with the rays of the median fins. These rays are sometimes pointed bones, which are then term- ed spines: but they are sometimes ossified only at F.o. 350.-DOR8AL Fm, supported on spiny rays, thejr ^ the remainder »•, r, and these resting on interspinous bones, 1. 1. being formed of a series of little cartilaginous pieces, jointed together ; and often branch- 8 BONES OP THE EXTREMITIES OF FISHES. ing at their summit ; these are termed articulated or soft rays ; the caudal fin is entirely formed of them (Fig. 346) ; and some- times there are no others. 544. The lateral fins, which represent the members, are ter- minated by rays similar to those of the vertical fins, and analo- gous to the fingers. In the pectoral fin are seen, at the base of these appendages, a transverse series of four or five small bones (c a, Fig. 348), which arc analogous to those of the carpus ; and these, in their turns, are fixed to two flat bones, a 5, which seem to be the radius and ulna widened. This apparatus is supported by a kind of bony girdle situated immediately behind the ears, on which the operculum or gill-cover is fixed ; and it consists of three bones, extending from the cranium to the hyoid apparatus, and prolonged backwards into a pointed process. The principal piece which enters into its composition, is that which bears the fore-arm, and which may consequently be regarded as the hume- rus, h ; it is united below with that of the opposite side and with the central prolongation of the hyoid apparatus ; and it is connected with the cranium by two bones (o, 0'), which are regarded by Cuvier as analogous to the scapula ; and lastly, the pointed process which is prolonged over the sides of the body, is ordinarily formed of two pieces, and may be compared to the coracoid bone, co. — The posterior member is less complicated; the rays of the ventral fin are only supported on a single bone, usually of triangular form, which is frequently attached to the central portion of the osseous girdle of the anterior member, and which, in other instances, is merely suspended by the muscles, having no bony connexion with the skeleton of the trunk. 545. In Cartilaginous fishes, such as the Rays and the Sharks (of which the Dog-fish is a common species), the arrangement of the skeleton differs from that which we have already described, and exhibits a great resemblance to that of the still cartilaginous skeleton of the Tadpole. The skull is not divided by sutures, and is only composed of a single piece ; this, however, is formed in other respects very nearly like the skull of ordinary Fishes. The upper jaw is formed by pieces analogous to the palatine bones and the vomer ; the maxillary and the intermaxillary do • LOCOMOTION OF FISHES. 9 not exist, and are only found in a rudimentary state, hidden under the skin. The lower jaw has in like manner only one piece on each side, and the opercular apparatus is altogether wanting. The vertebral column is sometimes chiefly formed of a single tube, pierced on each side for the passage of the nerves, but not divided into distinct vertebrae. The bodies of the vertebras are also frequently pierced through, so that the gelatinous substance which fills up the intervals of these bones forms a continued line through the whole column. The arrange- ment of the bones of the shoulder, of the pelvis, and of the fins, varies. Lastly, the hyoidean apparatus which supports the gills is usually formed very nearly in the same manner as amongst ordinary fish ; but in the lowest groups of this class (amongst the Lampreys for example) the branchial arches are absent. 546. The greater number of Fishes swim with great agility ; we are told that the Salmon, for example, advances sometimes with a rapidity of twenty-six feet in a second, and travels in one hour the space of from twenty to twenty-five miles. In general, it is through lateral strokes on the water, by the alter- nate bendings of the tail and the body, that they can move in this manner ; and the muscles which are destined to bend the vertebral column laterally, are so developed, that they usually constitute the greatest part of the mass of the body. The fins on the central line, that is to say, the caudal, the dorsal, and the anal, serve to increase the extent of this kind of oar : but the lateral fins — the pectoral and the ventral — act but little in progression, or forward movement ; and their principal use is generally to influence the direction of the course, and especially to support the animal in equilibrium. 547. A peculiarity in the organisation of Fishes, which is a great assistance to them in swimming, is the existence of a kind of bag filled with air, and constructed in such a manner as to be capable of being compressed at will. This swimming bladder is situated in the abdomen, under the spine, and fre- quently communicates with the ossophagus, or with the sto- mach, by a canal, through which the air contained in its interior can escape ; but this fluid does not appear to penetrate into it by 10 LOCOMOTION OF FISHES. f this passage, for it rather seems to be the product of a secretion, having its seat in a glandular portion of the walls of the reser- voir itself, which is sometimes completely closed. By the move- ments of the ribs, this elastic vessel is more or less compressed ; and, according to the space that it occupies, it gives to the body of the fish a specific gravity, equal, superior, or inferior, to that of the water ; and thus enables it to remain in equilibrium, to descend, or to rise, in this liquid. It has been remarked that it is often absent, and that it is generally very small, in the species destined to swim at the bottom of the water, or even to bury them- selves in the mud, such as the Rays, Soles, Turbots, and Eels. 548. Amongst a small number of Fishes, the pectoral fins have an extreme development, and thus permit the animal to support itself for some minutes in the air after it has leaped out of the _, _ FIG. 351.— DACTYLOPTERCS, ON3 OF THE FLYING FIOH. water. The Dac- tylopterus affords an example of this construction. There are some, which, by crawling, or by repeated leaps, can advance upon the ground. Some have been mentioned which can climb trees ; but these examples are very rare. 549. In treating of the organs for movement amongst Fishes, we must not omit to mention a very singular apparatus, which is seen in some of these animals, and which enables them to adhere with great firmness to foreign bodies. This is a flattened disc, which covers the upper part of the head, and which is composed of a certain number of cartilaginous and moveable plates, directed obliquely backwards (Fig. 352). The Fish of the genus Echineis are the only FIG. 352.— SUCKING- species which present this mode of organisation ; D.SCOFTHEREMORA.,^ one rffa^ ^liich lives in the Mediter- ranean and in the Atlantic, and which has been for a long time NERVOUS SYSTEM OF FISHES. 11 FIG. 353— REMORA. celebrated under the name of /femora, or Sucking-Fish,(Fig. 353) has been the subject of many amusing and absurd fables. It has been pretended that this small fish supports itself by a kind of suction through the disc just de- scribed ; and the power of stopping a large vessel in rapid progress has been attributed to it. A species allied to the preceding is very common in the waters of the Isle of France ; and it appears that, upon the coasts of Caffraria, it is employed in fishing, by allowing it to pursue fish, and then drawing it back, by means of a line attached to its tail, as soon as it has fastened itself upon its prey. 550. The life of a Fish is passed almost entirely in seeking its subsistence, and in flying from its enemies. Its external Senses only appear to give it a few obtuse impressions ; and its faculties are more or less limited. It shows no industry, nor any remarkable instinct ; its brain is very slightly developed, and its organs of sense are very imperfect. The cavity of the skull is small compared to the size of the body ; and the brain does not nearly occupy it. Be- tween its sides and the brain is found a spongy and fatty mass of a considerable size, particu- larly in adult individuals. The lobes which compose the brain are placed in a row, one behind the other ; in front we see the olfactory ganglia, oZ, often sepa- rated from the rest by a pedun- cle or foot-stalk ; next the cerebral hemispheres, ch ; then the optic lobes, op, which are often larger than the preceding ; then the cerebellum, ce ; and, behind all these parts, the lobes belong- ing to the medulla oblongata, sp. Via. 354.— BRAINS OF FISH an. A, Cod ; B, Shark. 12 ORGANS OF SENSE OF FISHES. 5ol. The nature of the integuments of Fish necessarily renders their sense of feeling very imperfect ; and deprived as they are of prolonged members, and particularly of flexible- fingers adapted to take hold of objects, it is only by means of their lips that they can exercise the sense of touch. The fila- ments which are often seen around the mouth, appear to inform them of the contact of bodies. The sense of taste must also be very nearly absent ; for their tongue is scarcely moveable, and is not fleshy ; it receives very few nerves, and the food never remains long in the mouth. The apparatus for smelling is of a much more complicated structure ; but is not arranged so as to allow either air, or the water serving for respiration, to pass through it. The nasal fossa only consists of two cavities, closed at the back ; each generally opens outwards by two nostrils, and is furnished by a pituitary membrane folded in a very remarkable manner. The ear is nearly always placed completely within the cavity of the skull, upon the sides of the brain ; and simply consists of a vestibule surmounted by three semicircular canals, at which the sonorous undulations can only arrive after having put into vibration the common integuments and the bones of the cranium. In general we see nothing that can be compared to the external ear, to the membrana tympani, or to the drum. Lastly, the eyes are very large and nearly immoveable ; they have no true eyelids, nor lachrymal apparatus. The skin is continued over the eye, and is thin enough to be traversed by the light. The cornea is almost flat ; the pupil very large, and but little or not at all contractile ; and the crystalline lens is sphe- rical. These organs generally do not usually present any pe- culiarity as to their position ; but amongst some fish there is a remarkable anomaly. Thus, amongst the Soles, Plaices, Turbots, and other flat-fish, they are not placed as usual on both sides of the head, but are both situated on the same side ; and this kind of mou- TEETH OP FISHES. 13 FIG. 3^6 — HKAD OK SHAKK. strosity coincides with a defect of symmetry in other parts of the body. 552. Fishes are very voracious ; there are only a few which live principally on vegetable matter ; and generally they swallow without any selection all the small animals which come within their reach. Some species are destitute of teeth, but amongst the greatest part, they exist in several rows, as in the mouth of the Shark, for example; and they are more commonly found, not only in the two jaws, but also on the palate, implanted on the vomer and palatine bones, — on the tongue, — upon the interior edge of the branchial arches, — and even in the back of the mouth upon the pharyngeal bones, which surround the entrance of the oeso- phagus. They have never any roots, but are fixed to the bones which support them ; they fall off nevertheless — probably by a mechanism analogous to that of the fall of the horns of the stag — and arc replaced by new teeth, which arise sometimes beneath, sometimes by the side of the old ones. The teeth with which the jaws are armed, only serve, in general, to hold or to crush the prey ; those situated at the bottom of the mouth are rarely (in existing fishes at least) disposed in such a manner as to reduce it. Their form varies very much ; sometimes they are so fine and closely set, that they present the appearance of velvet ; whilst in other instances they constitute strong hooks, plates with cutting edges, or rounded tubercles. 553. In the Lampreys, the mouth, instead of having the usual arrangement, presents a very singular structure. The cartilages, which amongst the Rays, &c. form the jaws, are here united into rings, and support a fleshy disc, the surface of which is furnished with teeth, whilst its centre is occupied by the mouth. The tongue also is supplied with teeth, and moves forwards 14 ORGANS OF NUTRITION OV FISHES. and backwards like a piston ; so that the animal can make use of this apparatus, either to fix itself upon another body, or to pump up the fluids which may form a part of its nourishment. It is commonly supposed that the Lampreys attach themselves by suction to the bodies of other Fishes, and then eat into their substance, but it seems more probable FIG.357.-MQUTHOFTHE fo()d animals. 554. The mouth is not surrounded by any salivary gland. The oesophagus is short; the stomach and the intestines vary in size and form. The liver is generally large, and of a soft tissue ; the pancreas is nearly always replaced by peculiar coecal append- ages placed around the pylorus ; the position of the anus varies much ; sometimes it is found under the throat, at other times under the tail. The kidneys are extremely large, and extend themselves on both sides of the vertebral column, through the whole length of the abdomen. Their excretory passages end in a kind of bladder, whose external opening is placed immediately behind the anus and the orifice of the reproductive organs. The digestive process appears to be performed very rapidly ; and the chyle is absorbed by numerous lymphatic vessels, which empty themselves by several trunks into the venous system near the heart. 555. The blood of Fishes, as already mentioned, is red; and the globules have an elliptical form, and are of consider- able dimensions. The heart is placed under the throat, in a cavity divided from the abdomen by a kind of diaphragm, and protected by the pharyngeal bones above, by the branchial arches on the sides, and in general by the humeral girdle behind. It is composed of one auricle, which receives the venous blood collected into a large sinus situated in its neighbourhood ; and of a ventricle placed beneath it, and giving rise at its anterior extremity to a branchial artery, which is swollen out at its origin into a bulb. This vessel soon divides into lateral branches, which are distributed to the gills ; and the blood, after having CIRCULATION OP FISHES. 15 traversed these organs, passes towards the head by another vessel, which in like manner runs along the edges of the branchial Branchial Artery Arterial Bulb»»v Venous Sinus1*— — Vena Porta, Liver, &c Intestine Vena Ca , Vessels of the Gills Dorsal Artery — Kidneys - Dorsal Artery or Aorta. Fro. 358.— CIRCULATING APPARATUS OF FISH. archos. These canals then send out some branches to the neighbouring parts, and are united together again to form a large dorsal artery, which passes backwards, beneath the vertebral column, and spreads its ramificationo to all parts of the- body. 16 RESPIRATORY APPARATUS OF FISHES. Finally, the venous blood is not all directly returned into the sinus, which we have before mentioned ; for that of the intes- tines and of some other parts, before being sent back into the heart, is distributed by the portal vein through the liver. We see, then, that the blood, in passing through the circle of the circulation, entirely traverses the respiratory apparatus, as amongst the Mammalia and Birds ; but in this course it only passes once into the heart, which consequently renders its pro- gress much slower. The heart itself corresponds in its functions to the right half of the same organ amongst the higher Yertebrata. 556. The Respiration of Fishes is effected by means of the air dissolved in the water ; and takes place at the surface of a multitude of projecting and very vascular membranous plates, fixed on the external edge of the branchial arches, the position of which has been already pointed out. In general there are on either side four gills, each composed of two rows of lengthened plates. In several of the Cartilaginous fishes, there are five, and in the Lamprey we find seven. Amongst nearly all the Osseous fishes these plates are simple, and fixed at the bottom only ; in a small number, such as the Hippocampus, commonly call- ed Sea Horse, thev are, on FIG. 359.— HIPPOCAMPUS. the contrary, ramified, and somewhat resemble bunches of feathers. Lastly, amongst the greater part of the Cartilaginous fishes, such as the Rays and Sharks, they are fixed to the skin by their external edges, as well as to the branchial arches by their internal. 557. The water necessary for respiration enters into the mouth, and by a movement of deglutition is forced through the openings which exist between the branchial arches, and thus arrives at the gills ; after bathing the surface of these, it escapes outwards by the opening of the gills. We see, in fact, the animal alternately opening the mouth, and raising its operculum. Amongst those fish whose gills are free at their external edge, it is sufficient to have one of these openings on each side ; but when the gills are fixed, it is necessary for the exit of the water te RESPIRATION OP FISHES. 17 nave an opening for every one of the spaces between the gills. Thus, in the Shark we find five, and in the Lamprey (Fig. 285) seven pairs. We can therefore know the arrangement of the respiratory apparatus, by the single inspection of its external openings. It is also observed that amongst some fishes, the water does not pass directly from the mouth into the respiratory cavity by the openings situated between the branchial arches, hut arrives there by a canal situated beneath the oesophagus, something like the trachea of the higher animals ; the Lampreys show this kind of structure. 558. Fish consume but a small quantity of oxygen ; some, however, are not satisfied with that which is dissolved in the water, and come to the surface from time to time to breathe air. There are even some which make use of it by swallowing it, and converting its oxygen into carbonic acid as it passes along the intestine ; the Loach of our ponds shows us an example of this singular phenomenon. When fish remain out of the water, they die in general very quickly from asphyxia ; not because they want oxygen ; but because the branchial plates, being no longer supported by the water, fall together, and thus cannot so easily be traversed by the blood ; and because these organs, when dried up, become unfitted to perform their func- tions. Thus, the fish that perish the most rapidly by exposure to the air have their gill- openings very wide, which facilitates the evaporation at the surface of the gills ; whilst those which resist it the best, have very small apertures, or else possess some receptacle, where they can preserve sufficient water to moisten these organs. The different fish which compose FIG. 360.— RESPIRATORY APPARATUS OP AW4BAS. the family of the Anabati- dae or Labyrinthiform Pharyngeans, are very remarkable in this respect, and owe their name to the cellular reservoirs of VOL. n. c F8 RESPIRATION AND HEAT OF FISHES. water placed above their gills. These reservoirs, situated under the operculum, and formed by the plates of the pharyngeal bones, effectually serve to retain a certain quantity of water, which keeps the gills- moist when the animal is in the air, and enables it to live there for some time : hence these fish are accustomed to leave the rivers and ponds, which are their usual abode, and convey themselves to considerable distances by crawling in the grass or on the ground. Those which present this labyrint'hiform apparatus in its highest degreo of complica- tion, and which have received the name of Anabas, not only FIG. 361.— ANABAS. remain very long out of the water, but can even, we are told, climb up trees. The greater part of the fishes of this family inhabit India, China, and the Moluccas. One species, the Gourami, which originally belonged to China, and which is much esteemed for its savoury flesh, has been naturalised in the ponds of the Isle of France and of Cayenne. . 559. As already stated, Fishes produce scarcely any heat ; that is, their temperature is usually but little above that of the medium they inhabit. The Tunny, Sword-fisfi, and their allies, however, constitute an exception to this rule ; for they are able to sustain a fixed temperature of about 90° ; and they are distinguished from other Fishes by the greater redness of their blood, which results from the larger proportion of red corpuscles. Several of this class have the singular power of developing Electricity, and of giving very strong shocks to the animals which touch them. The Torpedo, the Malapterurus, the Mormyrus, and a species of Gymnotus, are thus constituted ; and it is a remarkable thing that the electrical organ presents a very different conformation in each of them. ELECTRICAL FISHES; — GYMNOTUS. 19 FIG. 3II2.— GYMNOTUS. 560. It is the Gymnotus, or Electric Eel, which possesses this curious power in the highest degree. It inhabits Southern America ; and very much resem- bles the ordinary Eels, except that it has no fins along the back, and that its skin is without any visible scales. This fish attains about six feet in length ; its .body is long, and of uniform size, and its skin is covered with a viscid matter. It is very com- mon in the small streams and pools, which are met with here and there in the immense plains situated between the Cordilleras, the Orinoco, and the Banda- Oriental of South America ; and we find it also in the rivers Meta, Apure, and Orinoco. — The electric shocks which it gives at pleasure, and in any direction that it chooses, are sufficient to overcome men and horses ; and the Gymnotus has recourse to this means to defend itself against its enemies, and to kill at a distance the fish that it wishes to eat; for water, as well as metals, transmits the benumbing shock of this singular animal, — in the same manner as lightning-conductors convey the elec- tricity of the clouds from the atmosphere to the ground. Its first discharges are in general weak ; but when it is irritated and agitated, they become stronger and stronger, and are then terrible. When it has thus struck repeated blows, it becomes exhausted, and requires rest, for a longer or shorter time, before it recovers its power of giving fresh shocks. We are told that it employs this time in reloading its electrical organs, and that the Americans profit by this circumstance to take it without danger. In order to do this, they drive wild horses into the ponds inhabited by these fish ; which, receiving their first shocks, are soon stunned and overcome, or even killed ; they then seize the exhausted Gymnoti with nets, or with harpoons. 561. The apparatus by which the Gymnotus produces these disturbances lies along the back of the tail, and consists of c 2 20 ELECTRICAL APPARATUS OF TORPEDO. four longitudinal bundles, composed of a great number of parallel membranous plates very closely approaching each other ; these are nearly horizontal, and are united by an infinite number of other smaller plates placed vertically throughout. The small prismatic and transverse cells formed by the union of these plates, are filled with a gelatinous matter ; and the whole apparatus receives very large nerves. 562. The Torpedo is a flat cartilaginous fish, very much re- sembling the common Rays. Its body is smooth, and represents \ \ n? ^ n s FIG. 3 •>•:!- — COMMON \ TOHPEDO. \ *nr FIG. 364.— ELECTRICAL APPARATUS OP IHE TORPEDO :— c, brain ; me, spinal cord : o. eye and optic nerve ; e, electric organs ; np, pneumo-gastric nerves, proceeding to the electric organ; nl, branch from the preceding, covering the lateral nerve; n, spinal nerves running to the pectoral fins ; b, gills. very nearly a circular disc, whose anterior border is formed by two prolongations of the snout, which go on each side to join ELECTRICITY OP TORPEDO AND MALAPTERURUS. 2! Ihe pectoral fins; leaving between these organs, and the head and gills, an oval space, in which is placed the electrical apparatus of these fish. This apparatus is composed of a multitude of membranous vertical tubes, pressed one against the other, like the cells of bees, and subdivided by horizontal par- titions into small cells filled with mucous matter ; it is supplied by several very large branches of the pneumo-gastric nerves. It is in these singular organs that the electricity is produced, by which the Torpedo can give violent shocks to those who touch them, and produce the same phenomena which in physical experiments result from an ordinary electric current ; such as sparks, che- mical decompositions, &c. These fish arc less powerful than the Gymnotus ; but can nevertheless strike with sufficient force to benumb the arms of those who touch them ; and it is pro- bably by this means, that they seize their prey. It has been ascertained that this property is dependent on the posterior lobe of the Encephalon; and that by destroying this lobe, or by cutting the nerves which spring from it, the power of producing these shocks is destroyed. Several species exist in the seas which wash the whores of Europe. 563. The electrical Silurus or Malapterurus inhabits the Nile Fio. 365.— ELKCTRIC MALAPTERURUS. and the Senegal ; its length is from aboi»t ten to fourteen inches; and it appears to derive the power of giving electrical shocks from a particular tissue situated between the skin of the sides and the muscles, and having the appearance of a laminated ceHular tissue. The Arabs give to this fish the name of Raasch, which signifies thunder. 564. Fishes multiply by means of eggs ; and the number of these is sometimes immense, several hundred-thousands being often produced at a time. In general they have only a mucila- 22 MIGRATIONS OF FISH. ginous envelope, and are fertilized after they are laid. Some of these animals are, on the contrary, ovo-viviparous ; but whatever may be the manner in which the young fish are brought into life, they are from the moment of their birth completely abandoned to themselves, and many of them perish during the early period of their existence. There are a few species, however, such as the Gobies and Sticklebacks, which make regular nests for their young, composed of vegetable materials ; and tend them with great care. 365. It is to the simultaneous development of an incalculable number of eggs deposited in the same place, and to the instinct which induces different fish to follow each other, that we are to attribute the union of certain species in immense and closely- packed legions, called by fishermen skoals offish. We can hardly term these unions, societies ; the individuals of which they are composed do not assist one another; the same wants to be satis- fied keep them in the same locality, or remove them from it ; and if we see them occasionally following an individual as a guide, it is probably the consequence of a tendency to imitation, which always accompanies the first dawnings of intelligence. 566. However it may be, these animals, thus united in troops, often make long journeys, sometimes to gain the sea, sometimes to ascend rivers or to change their climate. Certain fish lead an almost sedentary life, and remain always in the locality where they were produced ; others are always wander- ing, and a great number of these animals periodically make journeys of greater or less length. At the time for spawning, they generally approach the coasts or enter the rivers ; and in this manner they sometimes effect an extremely long passage. Every year, towards tke same period, large numbers of migrat- ing fish arrive in the same places ; and it is generally believed that several of these species regularly migrate from the north towards the south, and from the south towards the north, fol- lowing a determined route ; but perhaps it would be more true to believe, that when they disappear from the shores, they only retire into the greater depths of the sea. The Herring is one of the most remarkable fishes in this respect, as well as the most celebrated on account of the importance of the fisheries of which MIGRATION OF HERRINGS. 23 it is the object. It inhabits the northern seas, and arrives every year in innumerable legions upon different parts of the coasts of Europe, Asia, and America, but never descends below the 45th degree of north latitude. Some naturalists think that all these shoals of herrings periodically retire beneath tlie ice of the polar seas, and set out from this common retreat in an immense column, which, by subdividing itself, is spread out over nearly all the coasts situated above the parallel which we have men- tioned. They have even gone so far as to trace upon the chart the journeyings of these shoals ; but this long migration, and this common rendezvous in the arctic regions, are far from being demonstrated ; and there is reason to believe that these events do not take place in this manner. It is very near our coasts that the herrings deposit their eggs, and it is probable that the young very soon retire into the depth of the sea, and there direct themselves towards the north, where they meet in great abundance with the small Crustacea and Animalcula, which are fitted to serve them as food. In the spring, other wants bring them towards the shore, and cause them to seek shallower and warmer water. They collect themselves into immense shoals, and descend towards the south ; but after having arrived in the Baltic, upon the coasts of Holland, and even as far as Brittany,' we do not see them retake the route to the north, to pass the winter under the ice of the pole, and to recommence in the following spring their pretended periodical journey. 567. However this may be, in the months of April and May, Herrings begin to show themselves in the waters of the Isles of Shetland ; and, towards the end of June and July, they arrive there in an incalculable number, forming large shoals, which sometimes cover the surface of the sea to an extent of several leagues, and which are several hundred feet in thickness. Soon afterwards, these fish are spread along the coasts of Scotland and England. During the months of September and October, they give place to larger fish ; and from the middle of October until the end of the year, they abound on the north coast of France, principally from the Straits of Calais to the mouth of the Seine. In July and August, they generally remain in the 24 MIGRATIONS OF HERRINGS AND SALMON. open sea ; but they then come into shallower water, and seek a convenient place for laying their eggs, where they remain until towards the month of February. The older Herrings deposit their spawn the first, and the younger ones afterwards ; but temperature and other circumstances also appear to have some influence on this phenomenon ; for in particular localities, we find eggs during nearly the whole year. After this period they are thin and but little esteemed ; fishermen then call them " shotten herrings."'* Their multiplication is prodigious ; there have been found more than sixty thousand eggs in the abdomen of one single female of moderate size. We are told that their spawn sometimes covers the surface of the sea for a great extent, and at a distance appears very much as if saw-dust had been spread there. Very little is known of these fish at an early period. 568. The Pilchard, the Mackerel, the Tunny, and the Anchovy, are also Fish of passage, which periodically visit the coasts, and give rise there to important fisheries. The Salmon is equally remarkable for its voyages : it inhabits all the northern seas, and every summer it enters the rivers in large numbers, and ascends nearly to their source. In these migrations the Salmon follow a regular order : forming into two long files united in front, and conducted by the largest female, who commences the march, whilst the smaller males form the rear-guard. These troops generally swim with a great noise in the middle of the stream, and near the surface of the water, if the temperature is mild, but nearer the bottom if the heat is great. In general the Salmon advance slowly and by leaping ; but if some danger appears to threaten them, the rapidity of their swimming is so great, that the eye can hardly follow them. If a dyke or a cascade opposes their progress, they make the greatest efforts to overcome it. By supporting themselves against a rock, and violently bending their body in a bow, they throw themselves out of the water, and jump sometimes to a height of from 10 to 16 feet into the air, so as to fall again clear of the obstacle which impeded them. The Salmon thus ascend rivers nearly to their source ; and then seek in the small streams and quiet places a . tin N: • MIGRATIONS OF SALMON. — FISHERIES. 25 bottom of sand and gravel, fit to receive their eggs. In the course of the autumn the eggs are deposited in a hole, which the female digs in the sand. The male then comes to fertilise em. They then remain through the winter in the fresh- water, nud descend to the sea with the early spring floods. The Ming Salmon grow very quickly ; and when they have attained to about the length of a foot, they leave the rivers to proceed to the sea, which they quit in turn t6 enter the streams, when they have attained the length of 16 or 18 inches, which is towards the middle of the summer that follows their birth. We have already seen that the Swallows, which at the approach of the cold season migrate towards the south, every year return into the same places. It appears that the Salmon has the same instinct. To ascertain this, a naturalist, named Deslandes, placed a ring of copper on the tail of twelve of these fish, and set them at liberty in the river Auzou, in Brittany. Soon afterwards they all disappeared ; but the following year, five of these Salmon were caught in the same place ; the second year, three ; and the year after, three more. 569. The habits of Fish show but few curious peculiarities ; but the history of these animals ought nevertheless to interest us, if only on account of the fisheries to which they give origin. At a period which is not very far removed from our own, this branch of industry occupied a fifth of the population of Holland ; and for the herring-fishery alone, that country covered all the northern seas with its vessels. In England it has supported a con- siderable number of good and hardy sailors ; and even in France, where it has less importance, there are computed to be thirty or forty thou- sand fishermen, of which nearly a third Fio. 366. — COD. venture every year as far as Iceland and Newfoundland to seek for the Cod, a large and excellent fish, which abounds in those parts of the sea, and which is found also, in comparatively small numbers, in our own seas. 26 CLASSIFICATION OF FISHES. •• 570. Until very recently the classification of Fishes most generally received was that of Cuvier, who made this group his peculiar study. After maintaining its ground as the system of Ichthyology for many years, this classification has recently been nearly superseded by one proposed by Professor Miiller of Ber- lin, which appears to furnish a much better means of arranging the numerous species of Fishes in natural groups ; and this will be adopted, with some modifications, in the present work. As, however, the system of Cuvier was, up to such a recent period, the one to which all authors referred in treating on Fishes, and the large and splendid work on those animals by MM. Cuvier and Valenciennes is arranged in accordance therewith, the fol- lowing short statement of its principal groups will perhaps prove useful to the reader. 571. The first division of the class is into the Osseous and Cartilaginous Fishes ; and this division has reference not only to the quantity of earthy matter in the skeleton, but also to the number of pieces of which the jaws are composed. The sub- class of Osseous Fishes is divided in the first instance into the groups Acanthopterygii, or spiny-finned, and Malacopterygii, or soft-finned, Fishes. In the former, the first portion of the dorsal, or the first dorsal fin (when there are two), always have spinous rays (§ 543); of which there are also some in the anal, and at least one in each ventral. In the latter, all the rays, with the occasional exception of the first dorsal or the pectorals, are soft or jointed. The Acanthopterygii are only subdivided into fami- lies ; but the Malacopterygii are divided into three orders, ac- cording to the position of the ventral fins. If these are situated under the abdomen, the fishes are Abdominal; if attached to the shoulder, they are Sub-brachial; and if wanting, they are Apodal. Each of these orders, especially the first, contains numerous families. Besides these Cuvier admitted two other small orders of Osseous Fishes, namely the Lophobranchii with tufted gills, and the Plectognathi in which the bones of the upper jaw and face are immovably attached to the cranium. 572. The sub-class of Cartilaginous Fishes is primarily divided into those having the extremities of the gill-filaments unattached CLASSIFICATION OF FISHES. 27 (as in Osseous Fishes) ; and those having them fixed. The former group constitutes but a single order Sturion€*s but the latter is again subdivided into those which have the jaws move- able and adapted for mastication, Plagiostomi; and those which have them soldered into a ring for suction. The latter are termed Cyclostomi, or circular-monthed Fishes. 573. In the system of Miiller above referred to, the primary division of the class of Fishes in accordance with the nature of the skeleton is done away with, as it is found that, by adopting this as the first point in classification, nearly allied Fishes are often widely separated ; and this is especially the case when the Fossil Fishes are taken into the account. The classification of Pro- fessor Miiller admits five primary groups of Fishes,* which he calls sub-classes, but which the majority of subsequent writers have agreed to regard as orders. Of these the first four unmis- takeably exhibit all the characters of vertebrated animals, pos- sessing a distinct vertebral column either of a bony or cartila- ginous texture ; a spinal cord dilated anteriorly into a brain, which is enclosed in a bony or cartilaginous brain-case (or skull) ; and a regular muscular heart composed of two chambers. The fishes of these four orders, however, present several important differences amongst themselves. Those of two of them have the bulb of the aorta, or the enlarged part of that vessel which issues immediately from the heart, covered with a strong muscular coat, which, by its contraction, appears to act in some sort as a second ventricle, giving an additional impulse to the blood on its expul- sion from the centre of the circulatory system ; whilst, to prevent the retrogression of the blood under this additional pressure, the inner wall of this part is furnished with numerous valves. The intestine in these Fishes also is provided with a curious spiral valve, attached by one edge to its walls, whilst the other projects freely into the cavity of the intestine ; thus forming a regular spiral canal, through which the alimentary matters are compelled to pass, on their way to the anus. These orders are, I. SELACHII, * Omitting the Dipnoi, a small order including the different species of Lepi- dosiren, which we have already referred to as belonging to the Batrachia ($ 534), but which form a sixth group of Fishes according to Professor Miillor. 28 CLASSIFICATION AND DISTRIBUTION OF FISHES. including the Sharks and Rays; the gills are fixed, and the water which has been made use of in respiration passes out through a series of openings corresponding in number to the gills and placed on the sides at the back of the head. The skeleton in these is always cartilaginous. II. GANOIDEI, or Enamelled Fishes, in which the gills are free like those of the ordinary Fishes, and concealed by an oper- culum. — In the other two orders the arterial bulb is furnished with thickened, but not muscular, walls ; its interior contains no valves, although a pair of these organs exists at its junction with the heart ; and the intestine is destitute of a spiral valve. III. TELEOSTEI, or Bony Fishes, with a bony skeleton, com- plete jaws, and free branchiae. IV. CYCLOSTOMI, or Lampreys, with a cartilaginous skeleton, no true jaws, a round sucking mouth, and sac-like branchial or- gans, opening by a series of small holes on each side behind the head. — The fifth order, that of the V. LEPTOCARDII, or Lancet Fishes, which includes only a single small species, forms the lowest step in the series of Ver- tebrated animals. The vertebral column is reduced to a mere gelatinous band, which supports a simple spinal cord, scarcely exhibiting any dilatation at its anterior extremity ; and the heart is entirely wanting, the circulation of the blood being effected by the pulsation of the larger vessels. 574. The class of Fishes is probably the most numerous of the whole Vertebrated series, both in regard to the number of families, genera, and species which it contains, and in regard to the number of individuals of the same species. The structure of a very large proportion of it has been but very imperfectly investigated ; and of the habits of these animals still less is known. Instead, therefore, of giving a technical description of every family, such as will be found in Systematic Treatises on Zoology, we shall confine ourselves to a notice of those groups which are of most general interest, either on account of pecu- liarities in their structure, or their importance to Man. It has been calculated that, exclusive of lakes and rivers, the seas oc- cupy full seven-tenths of the earth's surface. These seas yield DISTRIBUTION OF FISHES.- ORDER SELACIIII. 29 food even to the depth of several hundred feet ; and, as there is no obstacle in the water to bar the movements of Fish, we see that their pasture-grounds are almost unlimited in extent. Different tribes are formed to inhabit different situations ; thus we have some Fish adapted to live in fresh-water only, — others which can only live in salt-water, — and others, again, which can pass from the one to the other without inconvenience. Of fresh- water fishes, some are the inhabitants of rivers, others of lakes, whilst others prefer small streams. Of the marine fishes, some keep near the shore, whilst others pass most of their lives in the open sea ; some, again, float near the surface ; whilst others never rise much above the bottom. It is probable that we might regard the deeper parts of the ocean as divided (so to speak) into strata., each tenanted by certain species of fish ; for it is quite certain, that there is a particular range of depth, in which each species is usually found, and beyond which it seldom strays, either towards the surface or the bottom of the ocean. It is among the Fishes of shallow waters, and those which habitually tenant the higher stratum of the deep seas, that we find the most beautiful display of colours ; those of deep waters are for the most part comparatively dull in tint. This differ- ence is probably due to the absence of light, which seems neces- sary to the development of the most brilliant colours ; for the diminution in the intensity of the sun's rays, as they traverse water, is very rapid. What may be the absolute depth of water, at which all light ceases, and death and darkness reign, we have no direct means of ascertaining. It varies, of course, with the latitude ; since, the more obliquely the sun's rays fall upon the water, the less will be the depth to which they will penetrate. ORDER I. SELACHII. 575. Although Cuvier, taking the degree of ossification of the skeleton as his guide, placed the Selachii with the rest of the 33 ORDER SELACIIII; GENERAL CHARACTERS. cartilaginous fishes, below the« forms with a true bony skeleton, in which he has been followed by most subsequent writers, includ- ing even Professor Miiller, there seems to be sufficient reason for removing them from this degraded position, and placing them at the head of the whole order. In their general organisation they certainly stand higher than any other Fishes ; the development of the brain, and especially that of the cerebral hemispheres, is far superior to that of the other members of the class ; and this in- dicates a greater degree of intelligence. In some respects, in- deed, they approach the Reptiles ; and this appears to have been to a certain extent perceived by Linnaeus, as he arranges the whole of the Cartilaginous Fish, and a good many of the more singular Osseous forms, in his class of Amphibia. 576. The skeleton is always of a cartilaginous nature, ex- cept in a few species, in which the vertebral column is replaced by a gelatinous cord, called the chorda dorsalis, analogous to that which is met with in the embryonic states of other Fishes. The cartilaginous vertebrae of the majority of the order exhibit the ordinary conical cavities on their anterior and posterior sur- faces (§ 543), and their processes are inserted into small sockets, which are the small round holes seen in the dried back-bones of Sharks, sometimes manufactured into walking-sticks. The fins are usually of large size, and supported by strong rays ; amongst which some occasionally acquire the texture of dentine, or the fundamental substance of the teeth. The pectoral and ventral fins are always present, and the former are frequently of enorm- ous size, whilst the latter are furnished with peculiar filamentous appendages in the males of many species. The tail is always of considerable length and strength, and usually furnished with large fins, which are arranged in such a manner that the fleshy part of the tail reaches the extremity of the organ, generally forming the principal part of its upper branch. The Fishes in which this unsymmetrical structure of the tail occurs are called heterocercal ; they belong exclusively to this and the following order. The skin is sometimes entirely naked, sometimes beset with asperities of dentine ; these are sometimes of small size, and cover nearly the whole skin ; whilst in other cases they form large ORDER SELACHII; GENERAL CHARACTERS. 31 spines, scattered more or less abundantly over the surface of the body. The head is never covered with bony plates. 577. The structure of the bulb of the aorta has already been noticed (§ 573). The gills are completely fixed, the branchial arches being immoveable, and the gill-laminae attached by one of their margins to a series of partitions. These form several separate branchial sacs, into each of which the water penetrates from the pharynx through a separate slit, and from which it issues by a corresponding external aperture. Of these orifices, which are situated behind the head, there are usually five on each side ; but some Fishes have six or seven ; whilst in the curious Chi- nMeras, the water used in respiration is discharged through a single aperture, although the structure of the branchiae is the same as that of the typical species of the order. 578. By a peculiar arrangement of the reproductive organs, the majority of the Fishes of this order produce living young ; but a considerable number are oviparous, although in all cases the eggs are fecundated before their deposition. The eggs of the oviparous species are enveloped in curious oblong, horny shells, which are generally provided with filamentous appendages at the angles ; which are said, by clinging to sea-weeds and other sub-marine objects, to protect the young animal from being driven about and injured by the force of the waves. The empty cases are frequently cast up on the sea-beach ; they are well known under the names of mermaid's purses or sea-purses, and generally regarded by seaside visitors as some curious kind of sea-weed. 579. Besides the ordinary Sharks and Rays, this order in- cludes a singular small group of fishes, the Chimaeras, of which only a very few species are known. These, however, differ from the ordinary Selachii in so many remarkable characters, that they are regarded as forming a distinct sub-order, leading towards the ordinary fishes. The PLAGIOSTOMI, or typical Selachii, are readily distinguished by their possession of several branchial openings on each side ; whilst in the HOLOCEPHALI, or Chimceras, the water passes off from all the branchiae of each side by a single orifice. The latter form only a single family ; but the Plagiostomi are divided into two primary groups, which are further subdivided 32 THE EAYS. — FAMILY RAIID.E. into numerous families. The first of these groups is the tribe of the Rays (Raiina\ including six families ; whilst the second tribe, that of the Sharks (Squalina), includes no less than ten families. It will, however, only be necessary to allude particu- larly to the more important of these numerous families. 580. The Rays usually have the body so flattened, that the pectoral fins seem like a continuation of it; and these meet in front of the snout, and are prolonged backwards as far as the ventral fins ; thus giving to the whole body a nearly circular form. The eyes are situated on the upper side of the body, as in the ordinary Flat-fish (§ 551); but it will be observed that the plan of construction of the Rays and Skates is entirely dif- ferent from theirs, the two margins being here composed of the edges of the pectoral fins, whilst in the Flat-fish they are formed by the dorsal and anal ; and the Flat-fish habitually lying on one side, whilst the Rays lie on the abdominal surface, where we find their mouth and gill-openings. The position of the latter on the ventral surface is, in fact, the most characteristic distinction between these Fishes and the Sharks, in which the branchial apertures are placed on the sides of the body. The body is terminated by a long slender tail, which bears all the perpendicular fins (dorsal, anal, and caudal), but the caudal is sometimes wanting. These Fish live for the most part near the bottom of the water, on beds of sand or mud. When disturbed, they glide along in an undulating manner, with a slight motion of the pectoral fins ; and if attacked, they defend themselves by lashing violently witli the tail, which is often armed with sharp spines. They are all oviparous. In their habits they are ex- ceedingly voracious, feeding on fishes and Crustacea, and on naked or testaceous molluscous animals. The teeth are flattened and lozenge-shaped, forming a sort of mosaic ; and so powerful are the jaws, that they are capable of crushing the shell of a Crab with the greatest ease. 581. In the RAIID^E, or True Rays, the body is of a lozenge shape, with the snout pointed, and the pectoral fins forming rounded angles. The tail bears two small dorsal fins. This family includes all the best-known species of Rays, and several THE STING RAYS, EAGLE RAYS, AND ELECTRIC RAYS. 33 of them are constantly caught and brought to market in this country. One of the commonest is the Thornback, so named from the skin of its back being covered with a variable number of thorny tubercles of singular structure. This Fish is taken in abundance in the spring and summer, when it visits the shal- lows for the deposition of its eggs ; and it is an excellent article of food. It often attains a large size. 582. The TRYGONID^E, or Sting Hays, have no dorsal fin ; but the tail is armed with a single strong spine, notched on botlr sides, with which the Fish is enabled to inflict severe wounds upon its captors, although it does not appear that, as the ancients supposed, these are of a venomous nature. — The CEPHAL- OPTERID^, or Fin-headed Rays, which are nearly allied to the preceding, are distinguished from all the other Rays by a pair of curious little fins which stand out like horns from the FIG. 367,-STixG-RAY. head. These Fish, one species of which is found in the Mediterranean, often attain an enormous size. — In the two preceding families the teeth are of comparatively small size ; but in the MYLIOBATID^:, or Eagle Rays, so called from the great size of the pectoral fins, which not unaptly represent a pair of broad wings, the jaws are covered with broad hexagonal plates. In these fishes, the tail, the length and slenderness of which has obtained for them the name of Whip Rays, is armed, as in the Trygonidce, with a long serrated spine ; and in the Mediterranean, where one of the species occurs commonly, the fishermen dread this so much, that they cut off the tail of the fish as soon as pos- sible after its capture. 583. The TORPEDINID^E, or Electric Rays, of which a good many species are known, are distinguished from all the other rays by the rounded form and smoothness of their bodies. The common Torpedo is occasionally met with on the Channel-coast of England ; but it is more common in warmer seas, especially the Mediterranean. Its electrical powers have been already alluded to (§ 562). 584. In the RHINOBATIDJE, or Shark Rays, we meet with a 34 THE RAYS ;— RHINOBATID.E.— THE SHARKS. curious union of the characters of the Sharks and Rays ; the body being of an elongate spindle-shape, with the pectoral fins small, and of much the same form as in the Sharks, and the first dorsal fin situated above the ventrals. From the position of the gill-openings, and the nature of the teeth, however, they evidently belong to the Rays. They are found principally in the seas of warm climates ; and one Brazilian species is said to possess elec- trical powers. The most remarkable form is the Pristis, or Saw- fish ; so named from the extension of its snout into a long flat blade, furnished with a FIG. 368.— SAW-FISH. TOW of sharp spines, resembling teeth, on either side. With this formidable weapon the Saw-fish attacks the largest Whales, and inflicts very severe wounds. It sometimes attains the length of twelve or even fifteen feet. This Fish is very widely distributed, being found in the Arctic, Antartic, and tropical seas ; but it seldom approaches the shore. 585. The tribe of Sharks, as already indicated, differs from that of the Rays, in having the body of an elongated spindle- shape, the gill-openings placed on the sides of the body, and the teeth large and adapted for cutting. The nearest approach to the Rays is made by the family SQUATINID^:, the Angel, or Monk-fish, in which the body is somewhat depressed, and the pectoral and ventral fins large and broad, so that the Fishes re- semble the Rays a little in their external appearance. The common Angel-fish, or Monk-fish, is found not unfrequently in the British seas. It grows to the length of seven or eight feet, and, like the Rays, swims close to the bottom of the water, feed- ing voraciously upon the Flat-fish. — The SCYMNID^E, or Liches, are destitute of an anal fin, but possess two dorsals, neither of which are furnished with spines. The lobes of the caudal fin are nearly equal, and the head is furnished with a pair of small spiracles. The Greenland Shark, an inhabitant of the Arctic seas, is the best known species of this family. It attains a THE SHARKS; SPINACID^; GALEIDJB ; LAMNIDJE. 35 length of about fourteen feet, and is a deadly enemy to the Whales, attacking and biting them with great severity. It ap- pears to feed to a great extent upon the floating carcases of these gigantic Mammalia, biting large pieces out of them witli its enormous jaws, which measure nearly two feet across. It is a constant attendant upon the Whalers when they are engaged in cutting up their captures, but never appears to touch the men, although they often slip into the water amongst a crowd of Sharks. Its tenacity of life is very remarkable. The Greenland Shark is very subject to be attacked by a parasitic animal, be- longing to the class of Crustacea, which attaches itself to the eyes. The parasite measures from one to two inches in length, and its almost constant presence may give some countenance to the belief of the Whalers that the Shark is blind, as it never attempts to escape from a threatened blow with a lance or knife. The Greenland Shark sometimes occurs near the north- ern coasts of this country. 586. The SPINACID^E, or Picked Dogs, resemble the preceding Fishes in most of their characters, but have the dorsal fins furn- ished with a strong spine. The common Picked Dog-fish of our seas is so abundant, that as many as twenty thousand of them have been taken in one seine. It is about three feet long, and is said to be good food. The Picked Dog is also said to employ the spines of his dorsal fins as weapons, by bending himself into the form of a bow, and then striking out with great force. — The GALEID^E, or Topes, are distinguished from the preceding by the possession of an anal fin, and the absence of spines in the dorsals ; their caudal fin is very unsymmetrical. Two species, the common Tope and the Smooth Hound, are abundant in our seas ; the former has triangular, sharp, serrated teeth, like those of the rest of the Sharks ; but the latter has the jaws covered with a sort of mosaic, as in the Rays, and, like these, it feeds principally on Crustacea. 587. The LAMNID.E, or Porbeagles, have the tail nearly symmetrical, two unarmed dorsal fins, an anal fin, and two large spiracles ; the branchial apertures are all placed in front of the pectoral fins. The snout is of a pyramidal form. The common D 2 36 THE PORBEAGLE SHARK; NOTIDANID.E ; CESTRACIONTID.-E. Porbeagle Shark is about eight or nine feet in length, and is not uncommon in the British seas. Its English name seems to be compounded of Porpoise and Beagle ; for it bears some re- semblance to the former in shape, whilst it corresponds with the latter in its habit of hunting in packs. It is voracious in its habits, swallowing entire Fishes of two feet in length. The Basking Shark, which is also found in our seas, is a much larger species, and indeed is the largest of existing fishes, measuring sometimes no less than thirty-six feet in length. It is, however, by no means ferocious in its habits, and appears to feed principally upon small marine animals. It receives its name of Basking Shark, and also that of Sun-fish, which is applied to it in some localities, from its habit of floating at the surface of the water in calm warm days. Its branchial apertures are very large. — The NOTIDANID^E, which are closely allied to the Lamnidse, have only a single dorsal fin, and their branchial apertures are six or seven in number. Two species are found in the Mediterranean ; none of them seem greatly to exceed three feet in length. — The CES- TRACIONTID^E, of which only a single existing species is known, although the remains of extinct forms are very abundant in some —WHITE SHARK. of the earlier formations, have pavement-like teeth ; the front teeth are pointed, whilst the hinder ones are converted into regu- FAMILY CARCHARIDJE; WHITE SHARK, FOX SHARK. 37 lar flat grinders. The recent species is found in the Eastern seas, especially about the coasts of Australia. 588. In the CARCHARID.E, or True Sharks, to which we now come, the spiracles, which exist in the preceding families, are wanting, the dorsal fins are destitute of spines, and the an- terior one is placed nearly as far forward as the pectorals, whilst the tail is usually very unsymmetrical. Of the true Sharks, there are several species, of which the White Shark is the most notorious. It sometimes attains the length of twenty-five or thirty feet, and its mouth is sufficiently wide to enable it to receive the thigh or even the body of a Man. This species inhabits most of the seas of warm latitudes ; but it is rarely or never seen near our own shores. — The Fox Shark, or Thresher, FIG. 370.— Fox SHARK. is remarkable for the great development of the upper lobe of the caudal fin, into which the vertebral column is prolonged, this being nearly as long as the entire body. This Fish is occasionally met with on our own coasts, and sometimes attains the entire length of from twelve to fifteen feet. Its gape is not so wide, nor are its teeth so formidable in proportion to its size, as those of the preceding; but its tail is a powerful weapon, and it is exceedingly bold and voracious in its disposition. It has been stated on good authority, that it is not uncommon for a Thresher to approach a herd of Dolphins which may be sporting in unsus- picious security, and by one splash of its tail to put them all to flight, like so many hares before a hound ; yet the Dolphin is six times the bulk of the Thresher. — The Blue Shark bears more resemblance to the White in its general form, but is much smaller, not exceeding six or seven feet in length. It is very common off 33 HAMMER-HEADED SHARK; DOG-FISHES. — HOLOCEPHALI. the Cornish coast, and is extremely troublesome to the fishermen during the Pilchard-fishing season, cutting their lines and nets, and devouring the fish. — This family contains many other forms, more or less departing from the ordinary type ; amongst which we may mention the curious Zygcena, or Hammer-headed Shark ; FIG. 37L— HAMMER-HKADKI) SHARK. which resembles the ordinary Sharks in the form of its body, but has its head prolonged into the form of a double-headed hammer, with an eye in the middle of each extremity. It is occasionally met with in European seas, attaining the length of twelve feet ; and larger ones are said to inhabit the tropical ocean. 589. The SCYLLIID^E, or Dog-fishes, have a pair of spiracles, two dorsal fins placed behind the ventrals, and an anal fin ; their branchial apertures, which are of small size, are situated partly above the base of the pectoral fin. The species of this family are of small size, and exceedingly abundant ; three occur off our coasts. They are oviparous, depositing their eggs in the curious cases already alluded to (§ 578) ; and it is the empty cases of the eggs of these Fish which are so commonly thrown up upon our beach. 590. The sub-order of the HOLOCEPHALI, including only the single family of the CHIM.ERID.E, or Chimaras, differs from the THE CHIMERAS.— ORDER GANOIDEI. 39 Plagiostomi, as already stated, in the arrangement by which the water passes away from the branchiae ; the branchite themselves have the same structure as those of the Sharks, but the five pass- ages which convey the water from the branchial chambers unite so as to form a common external orifice, which is covered by a sort of rudimentary operculum. Thus these curious Fishes evidently form a transition towards those which are constructed on the ordinary type, in which the gills are free and covered by a movable operculum. The vertebral column in these Fishes is represented by a chorda dorsalis ; the upper jaw is wanting, and the superior teeth, of which there are four, are supported upon the front of the cartilaginous skull ; the lower jaw has only two teeth. They are oviparous, and lay large, flattened eggs, en- closed, like those of the oviparous Sharks and Rays, in a strong horny case. 591. The best known species is the Northern Chimcera, an inhabitant of the seas of high northern latitudes, which occurs, however, occasionally upon our shores. It is a Fish of a most extraordinary aspect, of a silvery colour, spotted with brown, with an obtusely conical snout, and a very long tapering tail. It usually measures three or four feet in length, and feeds princi- pally upon small fishes, usually following the shoals of Herrings in their migrations ; from which circumstance it has received the name of the King of the Herrings. It also feeds on Crustacea and other small marine animals. Another species is found in the southern seas, which is rendered remarkable by a singular cartilaginous process at the extremity of the snout, bearing some resemblance to a hoe. ORDER II.— GANOIDEI. 592. The order of Ganoid Fishes includes some remarkable living forms, which appear to constitute an intermediate group between the Cartilaginous Fishes just described and the Osseous or typical Fishes. The number of these Fishes now in existence is small, but in early periods of the geological history of our 40 ORDER GANOIDEI; GENERAL CHARACTERS. planet, the members of this order constituted almost the only re- presentatives of the class of Fishes in its waters ; and their fossil remains, preserved in the older strata of the earth, show the abundance and astonishing variety of forms which must formerly have existed in the waters of the ancient world. Some remarks upon these will be found in the paragraphs devoted to fossil Fishes, at the end of this chapter. 593. The character upon which the order of Ganoid Fishes was originally founded, and that to which its name refers, consists in the nature of the covering of the skin in most of its members ; this is composed usually of bony scales or plates, coated with a thin layer of enamel, so that the Fishes are, as it were, encased in a suit of bony armour. A somewhat similar structure, however, occurs, as we shall see, in many Fishes belonging to the following order; and these were accordingly included by Professor Agassiz, whose principal object was the facilitation of the study of fossil Fish, in the order of Ganoidei, as originally proposed by him. The primary characters adopted by Professor Miiller for the distinction of the order, as he circumscribed it, consist, as already stated, in the muscular coating of the bulb of the aorta, and the presence of valves in its interior, and in the existence of a spiral valve in the intestine ; whilst these Fishes are distinguished from the Selachii, in which these characters also occur, by their free branchiae and movable opercula. 594. In other respects the Ganoid Fishes exhibit a gradual transition from forms very nearly allied to the Selachii, to others which exhibit perhaps a still closer relationship to the true bony Fishes. The skeleton is sometimes cartilaginous, the vertebral column being even represented in some species by a gelatinous dorsal chord, and sometimes perfectly ossified; the skin is sometimes quite naked, sometimes covered with the bony plates above mentioned, and sometimes with horny scales with or without a coating of enamel ; but in most cases the head, at all events, is covered with enamelled plates of bone. The tail is sometimes heterocercal, sometimes symmetrical ; and the fin-rays are sometimes soft and flexible, sometimes divided like the soft rays of the fins of bony Fishes, and sometimes spinous. Each ORDER GANOIDEI; ACIPKXSERID.E. 41 opercuium usually bears a supplementary branchia, and below this there is frequently a false gill, which only receives arterial- ized blood. The top of the head is often furnished with a pair of spiracles, which also occur in some Sharks. 595. The recent Fishes of this order form five families. Two of these belong to the cartilaginous section of the order, the Chondrostei of Professor Miiller, — these are the ACIPENSERID^E, or Sturgeons ; and the SPATULARID^, or Leaf -nosed Sturgeons. The others belong to the Holostei of Miiller, possessing a true bony skeleton, — these are the LEPIDOSTEID^E, or Bony -pikes ; — the POLYPTERID^E, or Fin-pikes ; and the AMIID^E, or Bald- pikes. 596. In the ACIPENSERID^E, or Sturgeons, the body is more FIO. 372.- BELUGA. or less covered with bony plates, arranged in longitudinal rows ; and the head is armed with the same. The mouth is situated beneath the elongated muzzle, and is small, toothless, and pro- trusible ; in front of it a few longish barbs hang down from the snout. The air-bladder is very large, and communicates by a wide opening with the gullet ; and in this, and other points of their internal conformation, the Sturgeons show a considerable approach to the Lizards, whence they are ranked among the Sauroid fishes. The tail is very unsymmetrical. Sturgeons, like Salmon, ascend large rivers for the purpose of spawning ; and they are the subject of valuable fisheries. They are more abundant in the Continental rivers than in those of Britain ; id are particularly numerous in those which fall into the Black and Caspian seas. The common Sturgeon attains the length of six feet; but the great Sturgeon, or Beluga, has been found twelve or even fifteen feet in length, and weighing from 1200 to 3000 Ibs. The flesh of the former is very palatable and whole- some, resembling veal in its character ; that of the latter, how- 42 SPATULARIDJE. — LEPIDOSTEID.E, OR BONY-PIKES. ever, is not esteemed. The Sterlet is a smaller specie?, about two feet long ; which is found in the Russian rivers, and is con- sidered a great delicacy. All the species are valued on account of the excellent Isinglass which is yielded by their air-bladders ; and their roe is salted and prepared by the Russians, forming a dish termed caviare. More than 400,000 Ibs. of this have been prepared in the Caspian fishery in a single year. 5P7. The little family of the SPATULARIDJE includes a few fishes, nearly allied to the Sturgeons, in which the skin is quite naked ; they are also rendered remarkable by the production of the snout into a long leaf-like organ, often nearly as long as the whole body. The hinder margins of the opercula also are pro- duced far back, forming an acute angle, which reaches nearly to the middle of the Fish. The mouth is wide, and very different in its structure from that of the Sturgeons. These singular Fishes are found only in the large rivers of North America. 598. The LEPIDOSTEID^E, or Bony-pikes, constituting the first family of the recent Ganoid Fishes with an osseous skeleton, have the body of an elongated form, closely resembling that of the common Pike of our lakes and rivers, but covered with a num- ber of lozenge-shaped bony plates, arranged in oblique series, in which each plate overlaps the one beneath it, whilst it is attach- ed to its neighbour in the next row by means of a peculiar pro- cess. The jaws in these curious fishes are very narrow and elongated, and armed with a double series of conical teeth ; the tail is unsymmetrical, and both margins of the caudal fin, as well as the anterior margins of the other fins, are protected by a double series of sharp bony scales called fulcra. The head bears a pair of spiracles. One of the most remarkable peculiarities in the structure of these Fishes is presented by the vertebral column, which is composed of vertebra?, the bodies of which are united by regular articulations ; a structure which is only met with elsewhere amongst the Reptiles. The Bony-pikes inhabit the fresh waters of America, extending as far to the north as the great lakes. Several species have been described, some of them attaining a length of about three feet ; their flesh is said to be very good. POLYPTERID.E ; AMIID.E. — ORDER TELEOSTEI. 43 599. In the POLYPTERID^E, or Fin-pikes, the body is also covered with rhomboidal bony plates, but the fins are not furn- ished with fulcra. The head has a pair of spiracles, and the tail is slightly unsymmetrical. But the most singular character presented by these Fishes is the structure of the dorsal fin, which, instead of being continuous, is separated into a considerable num- ber (twelve to sixteen) of strong spines, distributed at short in- tervals along nearly the whole of the back, and each bordered behind by a small soft fin. Two species of this curious group are known, — one of them inhabits the Nile, and the other the Senegal. 600. The AMIID^E, or Bald-pikes, forming the last family of recent Ganoid Fishes, approach far more closely than the pre- ceding Fishes to the ordinary bony fishes. The skin is covered with small, rounded, horny scales, coated with enamel ; the cau- dal fin is scarcely unsymmetrical, and is destitute of fulcra, as are also the remainder of the fins; and even the peculiar structure of the arterial bulb, and of the intestine, is exhibited with far less distinctness than in the preceding groups, which may be re- garded as the existing types of the order. The species of this family, which are few in number and of small size, are peculiar to the rivers of South America ; they are said to feed principally upon small Crustacea. ORDER III.— TELEOSTEI. 601. We now come to the order of true Bony Fishes, which may be regarded as the typical order of the class. The general characters of the-e will be sufficiently understood from the com- parative statements already given, but they may be shortly re- capitulated as follows. The skeleton is almost always perfectly ossified, the only exceptions to this rule being presented by a few fishes, of which the skin is usually covered with bony plates, in which the vertebral column and its appendages are cartila- ginous ; but even in these the skull is completely ossified. The 44 ORDER TELEOSTEI; CLASSIFICATION. skin is usually covered with horny scales, but sometimes quite naked, and in a few instances more or less protected by bony plates. The gills are quite free, and protected by a movable operculum, which is often rather complicated in its structure ; the bulb of the aorta is thickened, but not muscular, and destitute of the internal valves of the Selachian and Ganoid Fishes ; and the intestine exhibits no trace of the spiral valve. 602. This order contains the great majority of the existing species of the class of Fishes, and its study is proportionately difficult, both from the number of groups into which it is neces- sary to subdivide it, and the difficulty which often occurs, as in all large groups of animals, in finding good characters for its subdivision, the different families often melting into each other so insensibly that it is hard to say where one ends and the other begins. 603. The great variety of organisation presented by the Bony Fishes has induced their division into six primary groups, or sub-orders, each including several families. These are, — A. PLECTOGNATHI, in which the bones of the upper jaw and face are firmly attached to, or amalgamated with, those of the skull. B. LOPHOBRANCHII, with the branchial filaments arranged in little tufts along the branchial arches, and the face produced into a long snout. In both these groups the opercula are confined by the skin, so that only a small aperture is left for the escape of the water. In the remaining groups, the bones of the upper jaw and face are more or less moveable, the gills are not tufted, and the opercular aperture is usually large. C. ACANTHOPTERI, with spinous rays in the anterior part of the dorsal fin, or in the first dorsal when there are more than one, and the inferior pharyngeal bones (§ 541) distinct. The air-bladder, when present, is completely closed. D. PHARYNGOGNATHI, in which the inferior pharyngeal bones are completely amalgamated, and usually armed with teeth. The air-bladder is closed. E. ANACANTHINI, with no spinous rays in the fins, and a completely closed air-bladder. PLECTUGNATIII; FAMILY G*M>UrMJMJC,3 ; DiOUOiN, SUN-FISH. 45 F. PIIYSOSTOMI, with soft fin-rajs, except the first in the dorsal, anal, and pectoral fins, which are occasionally spinous ; and an air-bladder which communicates with the pharynx by an open duct. A. — PLECTOGNATHT. $ 604. This group, which in many particulars seems to ap- proach the Selachian and Ganoid Fishes, includes only two families, distinguished by the mode in which the jaws are armed. In the first of these, the GYMNODONTES, or Fishes with naked teeth, the jaws are covered with plates of a substance resembling ivory. These are reproduced as fast as they are destroyed by wear ; and they constitute very efficient instruments for grind- ing down the food on which these animals live, — which consists of Crustacea and sea-weeds. To this family belong the Globe- fishes; which are so named from their power of distending them- selves into a spherical form, by inflating with air a large sac contained in the abdomen. When thus distended, they float along the water with the back downwards, swimming onwards by means of their pectoral fins ; and they are covered with a series of large spines, which are raised up when the body is thus inflated, so as to form a very efficient means of defence. From this last circumstance, these Fishes have been sometimes termed Pjarcupine-fish. There are three genera in which this curious power exists ; the Diodon (two-toothed), in which there is no furrow or division in the jaws, so that each seems like a single tooth ;— the Triodon (three-toothed), in which there is a division in the centre of the upper jaw ; so as to divide it, as it were, into two teeth; — and the Tetraodon (four-toothed), in which there is a division of this kind in each jaw. Besides these, this family contains the Orthagoriscus, or Sun-fish (so named from its rounded form), which looks like the anterior half of a fish cut in two in the middle. It has the power of floating with its head and eyes above water ; but not of distending itself with air ; in this state it moves along sideways, very slowly, however ; anil appears like a dead or dying fish. The Sun-fish (or Moon-fish, as it is sometimes called) attains a considerable size ; of the short 46 FAMILY BALISTID.E; FILE-FISHES, TRUNK-FISHES. species, which is most remarkable for its peculiarity of form, in- dividuals have been frequently caught measuring four feet in length, and nearly as much in breadth, and weighing 400 Ibs. ; and it has been stated occasionally to attain double that weight. 605. In the second family, that of BALISTID^E, or File-Jishes, the jaws are armed with a small number of distinct teeth, which are inserted into sockets in the jaws; the skin is Either rough, or covered with very hard scales, — whence their name, — and the mouth is prolonged into a sort of pyramid. In their general form, and in the brilliancy of their colours, they bear a consider- able resemblance to the Chaetodons (§ 613) ; and, like them, they inhabit the seas of warm regions, keeping near the surface, or in the neighbourhood of rocks. Some of them are remarkable for the appendages with which the body is furnished, which are especially striking in the Balistes peniciUi- gerus; their use, how- ever, is entirely un- known.— The Ostra- cions, or Trunk-fishes, should probably be placed in a distinct family, so remarkably are they distinguished by the mode in which the body is protected. The head and body are covered with plates of bone, soldered together in such a man- ner as to form an inflexible cuirass ; leaving only the tail, the tins, the mouth, and a small margin of the gill-opening, capable of motion, — all of which movable parts pass through openings of the cuirass. The greater part of the vertebrae also are soldered together. There are no ventral fins, and the Irs 1 and anal are small and are FIG. 373.— UALISTES PEMCILLIGERUS. J IG. 374.-TRVNK-FI8H. LOPHOBRANCHII ; FAMILY SYNGNATHID/E, OR TIPE-FISIIES. 47 placed fnr back; there is little flesh ; but the liver is large, and abounds in oil. The surface is often armed with spines. No sprcies of th( se singular Fish are known in the British seas. B. — LOPHOBRANCHIT. 606. This small group is separated from all other Osseous Fishes by the structure of the gills ; which, instead of hanging from the branchial arches in fringes of parallel fibres, disposed like the teeth of a comb, are set upon them in small round tufts, arranged in pairs. From this peculiar conformation, its name, which signifies tuft-gillcd, is derived. The gills are defended by a large operculum, which is attached by a membranous covering on all sides, except at one part where a small hole is left for the escape of the water. These fishes are also distinguished by having their body covered with shields or small plates, which often give it an angular form. In general they are of small size, and often without flesh. They form only a single family, that of the SYNGNATHID^E, or Pipe Fishes. They do not present many points of general interest ; but there are certain peculiar- ities in their organisation, which are very interesting to the Naturalist. In the Syngnathus, or Pipe Fish, which has a pro- longed muzzle like that of the Fistulariae (§ 607), the eggs are not deposited as in other Fishes, but are conveyed into a sort of pouch, formed by a doubling of the skin under the body of the male ; this pouch is under the abdomen in some species, and at the base of the tail in others. In this pouch the eggs become matured ; and when the fry are ready to escape, it opens and allows them to pass out. This contrivance reminds us of the pouch of the Marsupial Mammalia ; but there is this striking difference, that in the latter it is the Female which affords this protection to the young, whilst in the Pipe Fishes it is the Male. It has been asserted that, even after the young have quitted the pouch, they will return to it again ; and that the parent shows great attachment to them. The Hippocampus (Fig. 359} has a prehensile tail, unfurnished with any finny expansion ; and is 48 ACANTHOPTERI ; FISTULARIDJE ; TRIGLIDJE. enabled by its means to climb or hold on by the stalks of marine plants. It is only in the dead specimen, that the neck acquires the peculiar bend, which gives its head the resemblance to that of a Horse, from which its name is derived. The Pegasus, though furnished with a snout, has the mouth beneath it ; the pectoral fins are large, and are spread out in a wing-like manner ; whence these curious Fishes have derived their name, which signifies Flying Horses. C. ACANTHOPTERI. 607. This group, which must be regarded as including the types of the class of Fishes, is subdivided into a great number of families, the most important and remarkable of which alone will require to be especially noticed. In the family of the FISTU- LARID.X, or AULOSTOMID^:, commonly known as Sea Snipes, and Trumpet Fishes, the snout is produced into a long tube, at the apex of which the mouth is situated, much in the same way as in the Syngnaiki and other Lophobranchiate Fish. The skin is usually clothed with small scales, but sometimes naked ; and in one genus the back is covered with large plates. The Sea Snipe, the only Fish of this family that has ever been seen on the British coasts, is about four or five inches in length, and of a rather broad form, which has obtained for it the name of the Bellows Fish. The first dorsal fin is placed rather far back, and its first ray is produced into a long and strong spine. In the genus Amphisyle, in which the back is plated, this spine is placed quite at the extremity of the body, in a line with its axis ; and the second dorsal and caudal fins are situated in front of it on the lower surface of the fish. In the true Fis- tularias, which inhabit the Eastern seas, the body is elongated and cylindrical, and the first dorsal is represented by a series of five spines along the back. 608. The TRIGLID^E, or Fishes with shielded cheeks, are dis- tinguished by having the chain of small bones which forms the lower part of the orbit (§ 541) greatly dilated, constituting FAMILY TRIGLID^ ; GURNARDS, BULL-HEADS, STICKLEBACKS. 49 several large plates which cover the cheeks. The head is also usually armed with spines. Among these we may mention the Triylce, or Gurnards; of which we have several species on our own coasts ; they are known by the square form of their heads. The pectoral fins are usually large ; and in an allied genus, the Dactylopterus, or Flying Gurnard, they are of sufficient size to support the animal for a time out of the water (Fig. 351). The Gurnards emit a curious grunting or croaking noise at intervals, when taken out of the sea ; this they continue for some time, and it is from this that their name is derived. They are very tenacious of life ; and mostly swim near the bottom of the water. The swimming-bladder is usually large, and furnished with powerful muscles for its compression. To this group also be- longs the Coitus, or Bull-head, which has a large and horizon- tally-flattened head, eyes looking upwards, and its skin almost destitute of scales, and of a dusky hue : it lurks among stones in the beds of rivulets ; and its food consists of aquatic insects or small worms. The Scorpance, or Hog Fish, have the head flat- tened sideways, armed with spines, and adorned with curious membranous lobes and filaments ; they are marine fishes, asso- ciating in shoals, and haunting the rocky shores. Allied to these is the Sebastes, or Norway Haddock, which inhabits the northern seas, and is an important article of food ; the Greenlanders use its long spines as needles. Also belonging to this group is the Gasterosteus, or Stickleback, of which there are several species, some inhabiting salt water, and others fresh. The body has no proper scales, but is more or less plated at the sides ; and the abdomen is covered by a sort of cuirass, formed by a union of the pelvic and humeral bones. The common name of these fish is derived from the circumstance, that instead of possessing two dorsal fins, they have only one, the anterior being replaced by a set of sharp spines varying in number ; whilst the ventral fin is in the form of a sharp spine without any rays. These fishes are active arid rapacious, attacking other fishes with great ferocity, and devouring almost any small animal that comes within their reach. The Fifteen-spined Stickleback has been seen to undergo remarkable changes in its hue, under the influence of terror. VOL. II. £ 50 FAMILY PERCID.E ; PERCH, BASSE. The Sticklebacks are also interesting from the care taken by the parents of their eggs and young ; the former are deposited in a sort of nest made of fragments of vegetable matter, which serve as a habitation for the young for some time. The nest is made by the Male fish, which also watches over the safety of his pro- geny, and boldly attacks all intruders. 609. The principal and most typical family of this group is that of the PERCID^E, or Perches^ in which the body is more or less oblong, and covered with hard rough scales ; and the oper- cula and preopercula are toothed or spinous. The ventral fins are placed on the breast or throat. The branchiostegal rays are generally seven. Of this family our common Perch is a well- known example. The Perch is one of our commonest fresh- water Fishes, abounding in rivers, lakes, and ponds, especially such as are clear, lurking under the banks, and in other quiet situations. It is spread throughout the whole of temperate Europe, and is even found in Lapland ; other species are found in America, and in the tropical parts of the Old World. The food of the Perch consists of insects, worms, and small fishes, which it devours with great voracity ; and it may be rendered sufficiently tame to take these from the hand. Like the Carp, it is very tenacious of life ; and will live for many hours if packed in wet moss, and occasionally refreshed with water. The "Basse is a marine Fish, nearly allied to the Perch, in its general structure ; it is found on the whole line of our southern coast ; and associates in shoals, which at the spawning time fre- quent the mouths of rivers, and even advance up the stream to a considerable distance. It will not only live but thrive in fresh- water, if well supplied with food ; which, in its natural haunts, consists of small fishes and crustaceans. In the Polynemi, the ventral fins are placed a little behind the pectorals, and the latter have their rays produced into long filaments, which hang loosely on each side of the body, and are sometimes prolonged to twice its length, giving the Fish a very beautiful appearance. The Fishes of this genus are found in the seas of tropical climates ; they are usually very brilliant in their colours, and are regarded as most delicious articles of food. The Mango Fish of the Ganges TRACHINID-E ; WEEVER, STAR-GAZER ; MULLID^E. is a species of this genus ; as is also the Suleah-fish of Bengal, to which attention has been directed, as affording in its air bladder a large supply of excellent isinglass. 610. TheTRACHiNiD^E, or Weavers, which are included amongst the Percidce by many authors, have the ventral fins placed on the throat, and the scales smooth. In this group we find the Tra- chinus, or JVeever, which has the first ray of the dorsal fin ex- tended into a very long spine, and has also a strong spine on each operculum. This fish lies in the mud, and inflicts severe wounds with its dorsal spine, which the fishermen believe to have a poisonous power ; the bad character of the wound, how- ever, merely results from the rugged nature of the instrument which inflicts it. Something of the same kind is the case with the Perch ; the sharp spines in its dorsal fin having been known to lacerate the fingers of those who handle them incautiously. Another curious genus of this group is the Uranoscopus, or Star-gazer ; so called because the eyes are situated on the upper surface of the nearly cubical head, and directed towards the heavens. Within the mouth, behind the tongue, is a long nar- row slip, which the fish can protrude ; and which serves as a bait to attract the small fishes on which it preys, whilst it is it- self concealed in the mud. One species inhabits the Mediter- ranean ; but none of them are eaten. 611. The MULLID^E, or Surmullets, resemble the Perches in the position of their fins ; but their scales, which are large and easily detached, are nearly smooth ; their opercula are unarmed, and their branchiostegal rays are only four in number. They are marine fishes, some of them inhabiting our own coasts, and others of larger size being natives of tropical seas. The Mullus, or Surmullet, which has been in great repute among epicures from the time of the Romans, who used to feast tbeir eyes upon the changes of colour which the Red Mullet undergoes in dying, before they devoured its flesh, belongs to this family. This genus is quite distinct from that of the Mullets properly so called. The common Red Mullet is taken abundantly upon our coasts. 612. We may pass over the next three families with but little notice. They are all nearly allied to the Perches. The SPHY- E '2 52 SPHYILENIDJE ; SCLENIDJS ; SPARID^E ; CELETODONTIDJE. E, have the opercula unarmed, the scales, which extend over the sides of the head, smooth, and the ventral fins placed upon the belly. They are elongated, active, and predaceous fishes, with the jaws armed with formidable teeth; they live principally in the seas of tropical climates, although one or two species are found in the Mediterranean. The Barracuda of tropical America is a large and powerful fish, the bite of which is much dreaded ; its flesh, however, is a very palatable article of food. — The SCI^INID^E, or Maigres, also have the sides of the head scaly, but the scales are rough ; in the arrangement of the fins and the possession of teeth on the opercula they resemble the Perches, but the bones of the palate are not furnished with teeth. The Maigres are of large size, and very rapacious. They swim in little shoals, uttering a peculiar grunting noise, which is said to be audible even when the Fishes are at a considerable depth in the water. The common Maigre of the Mediterranean occurs occasionally on the British coasts. — The SPAKID^;, or Sea- Breams, are also large Perch-like fishes, which closely resemble those of the preceding family, differing from them principally in the want of spines on the opercula. They are generally found in warm climates. The teeth are sometimes acute, and sometimes broad and rounded, and adapted for crushing the shells of Mollusca. 613. From these we pass to the CH^ETODONTID^E, sometimes called SQUAMIPENNES, or Scaly-jinned fishes ; which are thus designated, from the soft, and even the spiny, portion of the dorsal fins being so covered with scales, as not to be easily dis- tinguished from the rest of their bodies. The body, too, is usually itself much compressed, or flattened laterally. The Chcetodons, which constitute the types of this family, are beauti- fully-coloured fishes of singular figure, abounding in the seas of the hotter climates. Their most common tints are black and yellow; but metallic blues and greens are not unfrequent. Sometimes the colours are disposed in spots; but mostly in stripes or bands. They generally haunt rocky shores ; and their flesh is considered excellent food. One species of this family, the Chelmon rostratus, is remarkable for the manner in which it FAMILY SCOMBERIDJE; — MACKEREL; TUNNY. 53 obtains its insect prey, by shooting drops of water from its long snout, so as to bring them down within its reach. Another fish of the same family, called the Archer (Toxotes jaculator), will in this manner shoot drops of water to the distance of three or four feet, rarely missing its aim. These fish inhabit the seas around Java ; and other species are found in different parts of the Indian seas. 614. The next family, SCOMBERID^E, or the Mackerel tribe, is one of the greatest importance to Man, from the large supply of wholesome and palatable food which it affords him. It consists of a number of species varying considerably in size ; but distin- guished by possessing a smooth skin, usually covered with a multitude of small smooth scales ; and by having a 1 irge and vigorous tail and caudal fin. They are divided into several groups, according to the form of the fins, tail, &c. In the first of these are associated the common Mackerel, the Tunny, and others, which are distinguished by having the hinder rays of the dorsal and anal fins separated into small fins. The Mackerel is remarkable for the beauty of its colours, in which it is almost pre-eminent among British fishes ; and for the rapidity with which it dies and becomes tainted, when removed from the water. The periodical appearance of large shoals of this fish upon our coasts, was formerly imputed to its migration from north to south. But many facts are opposed to this idea; and there can be little doubt that it is an inhabitant of the deeper parts of the seas around our island through the whole year, and that its appearance on our coasts is solely due to its seeking the shore, for the purpose of depositing its spawn. It is during the months of May and June that this takes place ; and these months, therefore, constitute the most active season for Mackerel fishing. This fish is most abundant on the southern coasts of England ; but instances have been mentioned, in which large shoals have been met with even off the coast of Greenland. — The Tunny is a rare fish on the shores of Britain ; but it is very plentiful in the Mediterranean, and has been known and celebrated from the remotest period of antiquity, at which we have any mention of Fish by particular names. It is a far larger and stouter fis.h 54 8COMBERID.E ;— BONITO ; SWORD-FISH. than the Mackerel, though bearing a general resemblance to it in form ; a specimen, which was caught when chasing Herrings into Loch Fyne, measured 7 ft. 10 in. in length, and weighed 460 ,lbs. ; but in the Mediterranean it FIG. 375. -TUN-NY. grows to a length of nearly twenty feet, and a weight of half a ton. The Tunnies, like the Mackerel, are dispersed through the ocean during most of the year ; but in the summer they resort to the shores in vast shoals ; and a fishery of great importance is then carried on along the north coast of the Mediterranean, and in the island of Sicily. The flesh of the Tunny, both fresh and salted, forms a considerable part of the food of the common people of those shores ; and the fishery constitutes a large source of profit to those who reside on the coasts. The Bonito or Striped Tunny, also a native of the Mediterranean, and a rare visitant on our shores, is a very hand- some fish, though smaller than the common Tunny ; it is further distinguished by its great activity and voracity, being one of the chief enemies of the Flying-fish; and, in common with the Tunny, it can sustain a higher temperature than most other members of its class. 615. Another remarkable group of Scomberida?, sometimes re- garded as constituting a distinct family, consists of the Sword- fish and its allies, which have the muzzle elongated into a spike, terminating in a sharp point, and forming a very formidable wea- pon. These fishes, of which there are several species.are FIG. 376.— SWORD-FISH. usually furnished with a high dorsal fin, by the agency of which they are enabled to propel themselves through the water with great energy. They sometimes attain the length of lo or even 20 feet ; and they do not hesitate to attack very large fishes (the Tunny, for example), PILOT-FISH. FAMILY ZENID.E. 55 transfixing them with their powerful spear. Instances are on record, in which even Men have been thus destroyed ; and it has not unfrequently happened that a Sword-fish has struck a ship, and has driven its sharp weapon through the planking. In the Mediterranean, where one species of Sword-fish is not uncom- mon, it is regularly pursued by the fishermen ; and its flesh is much esteemed in some places as an article of food. It is seldom seen, however, in large numbers together. — A third group of the Scomberidse is characterised by having the rays of the first dor- sal fin not connected, but existing as separate spines. Of this group we shall only stop to notice the Pilot-fish; which has been, from very ancient times, the sub- ject of many ficti- tious statements. By the ancients it was regarded as a sacred fish, from no 377.— PILOT-FISH. its being supposed to indicate their true direction to doubtful voyagers ; whilst by sailors of the pre- sent day it is commonly regarded as a guide to the Shark in its pursuit of prey, and is said to tempt it to take the bait which has been thrown out for its capture. Certain it is, however, that the Pilot-fish will often follow the wake of ships for many hundred miles ; thus an instance has been known, in which a vessel was accompanied by two of this species, during its whole voyage from Alexandria to Plymouth, which occupied 87 days. The common Pilot-fish of the Mediterranean and Atlantic does not much exceed a foot in length ; but there is a species on the South American coast, which occasionally attains eight or nine times those dimensions. 616. The family ZENID^E strongly resembles the preceding; but differs from it in the high and compressed form of the body. Many of the species composing it are remarkable for the fila- mentous prolongations of their fins. This is the case with one of the types of the family, the Zeus or Dory, the peculiar form and ing 56 FAMILY ZENID.E; — DORY; BLEPHARIS. aspect of which will be better understood from the accompany! figure, than from any technical description. This fish has been in great repute amongst epicures, even from the time of the Romans ; it is not very com- mon upon our own coasts, being nearly restricted to Devon and Cornwall ; but it is more abun- dant in warmer la- titudes. The name John Dory, by which it is com- monly known in this country, is evidently a corruption of the French jaune dore, or golden yellow ; which applies to the colour FIG. 378.— THE DORY. FIG. 379.— BLEPHARIS. of its lighter parts when the fish is alive. Another fish of thia family, no less remarkable for its form, is the Blepharis ; of which ; TEUTHID^; NOTACANTHID.E ; CEPOLID^. 57 one species, inhabiting the West Indian seas, is known under the appellation of the Cobbler-fish, probably on account of the long thread-like appendages for which it is so conspicuous. The use of these curious appendages is altogether unknown. 617. The CORYPH^ENID^E, or Dorados, which have fre- quently been placed amongst the Scomberidce, are distinguished by their compressed bodies, surmounted by a very high dorsal fin, running nearly all the length of the back, and all the rays of which are flexible, although the anterior ones are undivided. The anal opening is placed very far forwards, the abdominal cavity being of small size ; and the anal fin, which is of great depth, usually extends forward nearly to the pectorals. The ven- tral fins are very small, or entirely wanting. These Fishes are exceedingly active and voracious ; they are for the most part inhabitants of the seas of warm climates, but one species is found in the Mediterranean. This is the Dorado, the Dolphin of the ancients ; it is a large and splendidly-coloured fish ; celebrated for the velocity of its movements, and for the variety of tint which its surface exhibits under a play of light. The changes of hue which it undergoes when dying, were a source of great admiration to the luxurious Romans ; by whose poets this Fish was much celebrated. It is one of the greatest enemies of the Flying Fish. The Dolphrh of the moderns is not a Fish at all, but a Cetaceous Mammal (§ 211). 618. Three other small families, allied to the Mackerels, re- main to be noticed. Of these, the TEUTHIDJE seem to unite the Mackerels with the Chaetodons ; but they are distinguished from both by their possession of several prickles, or a large sharp spine, on the sides of the tail. With this spine some of the species can inflict severe wounds when incautiously handled ; and a West Indian species is called the Surgeon from this circumstance. The Teuthidas are among the few Fishes which live on sea-weeds. The NOTACANTHIDJS are of an elongated eel-like form, and have the caudal extremity surrounded, as in the Eels, by a continuous fin. In the CEPOLID^E, or Ribbon-fishes, the body is also greatly elongated, but it is at the same time much compressed. The dorsal fin is very long, often running the whole length of the back j but 58 ANABATID^E. — MUGILID^E; MULLETS. the caudal fin, when present, is always distinct from the dorsal. They are found, but not abundantly, in most seas, and some of them attain a large size; the Gymnetrus Banksii, a British species, being sometimes twelve feet long. 619. The peculiar structure of the succeeding family, ANA- BATID^E, has been already mentioned (§ 558) ; and it adapts them to a mode of life which the circumstances of this climate do not render necessary. In cold or temperate regions, the ponds and streams, which are capable of supporting fish at all, are not dried up, except in seasons of extreme drought: but in tropical coun- tries there are many situations, in which there is an ample supply both of food and water for Fish during the rainy season ; but a complete deficiency of both, when this is succeeded by the periodical drought. Such receptacles can only be tenanted by Fish, which, like the Anabas, are furnished with the peculiar pharyngeal apparatus (Fig. 360) for keeping the gills moist ; since, when one pond or stream is dried up, they can migrate in search of another. In the course of these journeys, they climb up steep banks, and even trees ; and by a remark- able instinct, they seem always to travel towards the nearest water. This family contains a considerable number of genera, all of which are inhabitants of fresh-water ; none have been hitherto found except in the south-ea^t of Asia and the adjacent islands, and in Southern Africa. 620. This family is succeeded by that of MUGTLID^E, or the true Mullets; which are distinguished by several remarkable peculiarities of structure. Their body is nearly cylindrical, and is covered with large scales ; the head is broad and flat, and is covered with large angular sca'y plates ; and the stomach is fur- nished with fleshy walls, giving it a resemblance to the gizzard of a Bird. The Mullets associate in large shoals, and chiefly inhabit the mouths of rivers, where they are often seen making high leaps. They feed upon small Crabs and other Crustacea, which they swallow entire ; and the almost total want of teeth is compensated by the powerful gizzard, which serves to grind down their food. The Grey Mullet is one of those fishes, which, habitually living at the mouths of rivers, where BLENNIID.E ;— BLENNIES , SEA-WOLF. 59 the salt and fresh waters mix, will thrive well in the latter alone. 621. We may next mention the BLENNIID^E, or Blennies, which are elongated Fishes, having a single dorsal fin, almost entirely sup- ported simple upon flexible rays. The ven- tral fins are placed in front of the pectorals, and have only two or three r;iys in each. They live in small troops near the coast ; and they can exist for some time without water (their gill-openings being small), especially if kept in moist grass. Many of this family retain their eggs until they are hatched within the oviduct ; so that the young are produced alive, fully formed, and capable of finding their own subsistence. The Anarrhicas, or Sea-Wolf, must be referred to this family, al- i lot. 380.— BLENNV. FIG. 381. ANAIIRHICAS LUPUS. though differing from it in possessing no ventral fins, and in having the jaws and palate armed with large tubercular teeth. — This fish may be almost regarded as replacing the Sharks in the Arctic seas ; for it attains the length of six or seven feet, and is extremely voracious and bold. Its body, though massive, is adapted for active and energetic motion ; and its powerful bite makes it a very formidable enemy. It often enters the fisher- men's nets, for the purpose of plundering them of the entangled 60 GOBIID.E ; — GOBIES ; LUMP-FISH ; REMORA. fish ; and when the fishermen attack it, and it cannot dart through the net, it fights like a Lion. On the east coast of Scotland it is not an unfrequent visitor ; and its appearance and habits cause it to be regarded with great dislike ; nevertheless its flesh is wholesome and palatable. It is understood to prey indiscriminately upon Fishes, Crustacea, and shelled Mollusca ; its jaws and teeth being capable of breaking the hardest shell. 622. In the family GOBIID.E, or Gobies, we find the same simple flexible rays in the dorsal fin as in the preceding group ; but the ventral fins are united beneath the chest, forming a sort of conical sucker, which the Fish seem to use for the purpose of occasionally attaching themselves to solid bodies. They live, like the Blennies, near the shore, and prefer a clayey bottom, in which they excavate canals, wherein they pass the winter. In spring, they prepare a sort of nest, with sea-weed ; in which the young (often produced alive, as in the Blennies) are protected ; and the parents exert themselves considerably to bring them food and to defend them from their enemies. Several species of Goby exist in the European seas ; but none of them are of much size, or of any direct value to Man. In other seas numerous genera exist, more or less allied to the Gobies of our own coasts. The family of the Gobies includes two singular forms of Fishes which require some notice. One of these is the Cyclopterus, or Lump-fish, a curious, shapeless creature, of a purplish black tint, with thick fins and rows of tubercles along the back and sides. The ventral fins form a large and powerful sucker, by means of which the Fish adheres with astonishing firmness to any object under water. Pennant says that a pail containing several gallons of water could be lifted by the tail of one of these Fishes which had attached itself to the bottom. — The Remora, or Sucking-fish, also belongs to this family ; although its ventral fins are only united at the base. Its singular sucking disc has been already referred to (§ 549). 623. There are certain spiny-finned Fishes, in which the carpal bones are so elongated, as to form a sort of arm or wrist, to the extremity of which the pectoral fin is articulated. This conformation (an approach to which is seen among some of the FAMILY LOPHIID.E; FISHING FROG. 61 Gobies) gives to the Fishes which possess it a very strange appearance ; and enables them, in some instances, to leap up suddenly in the water, and seize the prey which they observe above them ; in other cases to leap over the mud, somewhat after the manner of Frogs. From the very peculiar genus Lophius, or Fishing Frog, in which this character is combined with some offiers of a very extraordinary nature, the family may be designated as that of LOPHIID^E, or Anglers. The com- mon Angler of our own coasts has an enormous flattened head, which constitutes the chief bulk of the Fish ; and a tail so com- pressed on each side, that the creature seems composed of little else than head and tail. On the former, in front of the eyes, are two long rays or filaments of a horny substance ; and there are also four others of a similar nature, but shorter, on the head. The mouth also is furnished with numerous worm-like append- ages ; which seem to represent the tentacula or prolonged lips of many Invertebrated animals. This animal is described as concealing itself amongst marine plants, or behind hillocks of sand, rocks, and stones ; when it opens its great mouth and attracts small fishes as they swim past, by giving a wriggling motion to the appendages just mentioned, which causes them to mistake these for worms ; so that, in attempting to seize them, they fall an easy prey to their subtle and voracious enemy, being speedily engulfed between its enormous jaws. The hideous appearance of its monstrous and constantly-open mouth, well armed with teeth, has gained for the Angler ,the vulgar name of Sea Devil. There are few parts of the British shores where it is not to be occasionally met with ; and when captured in nets along with other fishes, it speedily begins to swallow its companions. On some coasts it is sought for, on account of the live fish in its stomach. In the Museum of the College of Sur- geons in Dublin, there is a skeleton of an Angler, about two feet and a half in length, in the stomach of which is the skeleton of a Cod. two feet long, — in whose stomach again are contained the skeletons of two Whitings of the ordinary size, — and in the stomach of each Whiting there lay, when it was first examined, numerous half-digested little fishes, which were, however, too 62 CHIRONECTES. — PHARYNGOGNATHI. small and broken-down to admit of preservation. The Frog- fish, with all these contents, had been taken by the fishermen, and offered for sale in the market as an article of food, without any reference at all to the size of its stomach, which was not at all unusual. The contained fishes must have been all swallowed on the morning on which the Angler was taken : as they were all, with the exception of the smallest, equally fresh and undi- gested.— The Chironectes, or Hand- fish, bears a strong resem- blance to the common Angler in its structure and habits ; but its fins are still more capable of motion, enabling it to walk along the ground almost in the manner of quadrupeds, — the ventral fins, however, in consequence of their advanced position, serving as the fore-legs, and the pectoral fins performing the office of hind- legs. In some of the muddy estuaries of the north coast of Australia, from which the tide ebbs far back in the dry season, these Frog-fishes are abundant, and capable of taking such vigorous leaps, that those who have visited these places have, at first sight, mistaken them for birds. Their gill-open- ings are very small ; and they can live out of the water for two or three days. They have the faculty of inflating their large stomachs with air, so as to give themselves the form of a bal- loon,— in this respect corresponding with the Diodon. D. — PHARYNGOGNATHI. 624. The Pharyngognathi, or Fishes in which the inferior pharyngeal bones are united, are sometimes furnished, like those of the preceding group, with spinous rays in the dorsal fin, whilst in other cases these rays are wanting. By Cuvier and the sub- sequent writers, therefore, these fishes were divided between his two principal groups of bony fishes, the Acanthopterygii and Malacopterygii. Of the four families composing the group, three exhibit the structure of the fins characteristic of the former group, but the spinous rays of the anterior part of the dorsal fin are usually furnished with a peculiar little membranous ap- pendage near the extremity, which does not occur in any other fishes. WRASSES; PARROT-FISH; GAR-FISH. 63 625. The LABUID.E, or Wrasses, forming the first family of the spiny-finned species, have fleshy lips, smooth scales, and an uninterrupted lateral line. The lower pharyngeal bones are completely fused together, and furnished with broad grinding teeth. The mouth is protrusible and armed with large teeth, and the colours are for the most part very brilliant. Several species are found upon our own coasts, but they are not in much repute, and are known among the fishermen by the name of 'k Old Wives of the Sea." They chiefly frequent rocky shores, and for this reason are often called Rock-fish. — This family also includes the remarkable genus Scarus, or Parrot-fish ; which is furnished with large convex rounded jaws, and these are covered with hard, scale-like teeth, which succeed each other from the rear to the front in such a manner, that the bases of the newest form a cutting edge. Numerous species of these Fish inhabit tropical seas ; many of them are remarkable for the brilliancy of their colours. These Fishes appear destined to restrain the ex- tension of the stony Corals, on the newest layers of which they are enabled, by the immense strength of their jaws and teeth, to browse without difficulty, — digesting the animal matter it con- tains, and setting free the carbonate of lime in a chalky state. — The POMACENTRID^E, or Spiny Wrasses, have the lower pha- ryngeal bones fused together like the Wrasses, but their scales are rough, their lateral line is interrupted, their preopercula are toothed or spinous, their lips are not fleshy, and the spinous rays of the dorsal fin are destitute of membranous appendages. They are found in the seas of hot climates. — The CHROMIDJE, on the contrary, are generally inhabitants of the fresh waters ; they re- semble the preceding in many respects, but possess a smooth preoperculum and the fleshy lips of the true Wrasses. Their pharyngeal bones are united by a suture. Unlike the Labridcr, which are very indifferent eating, these Fishes appear to be good, and one species which is caught in the Nile is looked upon as one of the best fishes produced by that river. 626. The soft-finned species of this group all belong to the family of the SCOMBERESOCID.E, or Gar-fish, the scientific name of which has reference to the resemblance presented by its mem- 64 GAR-FISH; FLYING-FISH. bers to both the Mackerels and Pikes. The body is usually much elongated, the skin is covered with small scales, the ven- tral fins are placed on the abdomen, and the dorsal and anal fins are removed very far back towards the caudal. The Gar-fish, or Sea- Pike, has a very elongated mouth, which is well furnished with teeth. It is quick and active in the water ; swimming with considerable rapidity near the surface, and leaping and gambolling as if in the exuberance of vivacity. This Fish comes in shoals to the southern coast of Britain, in the months of April and May ; and from its appearing a short time before the Mac- kerel, it is termed by the fishermen the Mackerel-guide. It is not in much esteem as an article of food. — To this group also belongs the JExoccetus, best known as the Flying-fish ; which is remarkable for the enormous development of its pectoral fins, and for its power of sustaining itself upon them out of water. It is necessary to bear in mind that the term Flying-fish has been applied to this genus, in common with the Flying Gurnard (§ 608) ; and that, although really so different, they have been continually confounded together in the accounts of voyagers. The term Flying-fish ought to be restricted to the Exocoetus ; which is the one that best deserves it. Various species exist in different parts of the seas of warm latitudes ; and our own coast has been occasionally visited by them. As elsewhere stated (ANIM. PHYSIOL. § 667), their flight through the air seems en- tirely to depend upon the impulse they receive from the stroke of their fins upon the water, at the moment of quitting it. They are to a certain degree supported by their wing-like fins, while sailing through the air ; but they do not seem able to raise or to propel themselves by striking them against it. The most usual height of their flight is from two to three feet ; but they have occasionally been known to spring to a height of fifteen or even twenty feet. The utmost length of their flight seems to be be- tween two and three hundred feet; and its extreme duration about thirty seconds. •• Few spectacles are more beautiful than the sudden rise of a shoal of Flying-fish from the gently-undu- lating surface of the tropical ocean, — their scaly surface and ex- tended fins glistening in the bright sunshine with all the varied FLYING-FISH.— FAMILY GADIDJE. 65 hues of the rainbow, — and the graceful curves in which they move at last terminated by a return to their native element, from which they presently again spring up with renewed vigour. These airy excursions are commonly regarded as occasioned by the pursuit of Dorados, Bonitos, and other fishes of prey ; but this is probably by no means the case, for the Flying-fish seem frequently to .rise from the water for the mere sake of exercis- ing, with pleasure to themselves, those powers of movement with which they are endowed, — just as we see other fishes gamboling about in their usual medium. Whilst in the air, they are often seized upon by the long-winged sea-birds. E. — ANACANTHINI. 627. The fishes of this group are distinguished by the total absence of spinous rays from all the fins, and by the possession of a completely closed air-bladder. Their ventral fins are usu- ally present, and situated either on the breast or throat ; the fishes presenting this structure were called by Cuvier Mala- copteryg'd Sub-brachiati. Of the four families included in the group, however, two are destitute of ventral fins. The two fami- lies in which the ventral fins exist must be reckoned amongst the most valuable of Fishes. In the first of these, that of the GADIDVE, or the Cod tribe, the body is long, rather slender, taper- ing off into a long and powerful tail ; the skin is covered with small soft scales, and the fins are of large size. They live, for the most part, in the seas of cold and temperate climates, and are exceedingly active and voracious, feeding upon most of the smaller aquatic animals. From their considerable size, and their tendency to congregate in particular localities, as well as from the wholesomeness and good flavour of their flesh, they are pro- bably of more importance to man than any other family of Fish. The Cod-fishery on the banks of Newfoundland sends a vast supply to almost every part of the world ; and the amount caught on the British shores is also very considerable. The appearance and quality of the fish vary considerably, according to the nature 66 COD; HADDOCK, ETC. — PLEUB,ON7ECTID.E, OR FLAT FISH. of the ground on which it is taken. Their reproductive powers are enormous ; the roe of a single female having been estimated to contain nine millions of eggs. Nearly allied to the Cod, are the Haddock, Whiting, Hake, Ling, Rockling, Coal-fish, and others. The first of these is considered as the most delicate of the whole family, when fresh ; but it does not take salt well ; and for pre- servation, the Cod and Ling excel the rest. The Burbot, or Eel- pout, a fish nearly allied to the Ling, inhabits the rivers and lakes of some parts of Europe and Asia. It is found in some English rivers. 628. The second family consists of the PLEURONECTID.E, or Flat-fish. These present several remarkable peculiarities of structure ; by which they are distinguished, not only from all other Fishes, but even from all other Vertebrated animals. Their body is extremely compressed, or flattened at the sides; the animal, however, does not habitually swim with these sides erect in the water, but usually lies flat on the bottom, one side being in contact with it, and the other being directed upwards. The lower side is generally white, whilst the upper is brown ; and the former is commonly (but erroneously) regarded as the belly of the fish, and the latter as its back. The dark colour of the upper surface harmonises with that of the bed on which the fish lie ; so as to enable them to conceal themselves from their foes, or to watch for their prey, without being themselves ob- served. Individuals are occasionally met with, in which both sides are coloured alike ; these are said to be " Doubles." It is usually the coloured side which is doubled ; though it is occa- sionally the white one. By a change in the position of the head, both the eyes are brought round to the right side, so as to look upwards, when the fish is lying on the bottom ; this change may be designated as a sort of twisting round ; but it also in- volves an unequal development of the bones on the two sides of the head, which shows itself in the mouth. Of the pectoral fins, too, one is usually larger than the other. The dorsal fin is con- tinued along the whole of the ridge of the back, from the head to the tail ; and the anal fin usually forms a like continuous ex- pansion below, sometimes uniting with the ventral fins. The FLAT-FISH; — TURBOT, ETC. 67 anus is thus brought very close to the head, and the abdominal cavity is exceedingly small, so that the greater part of the body of the Flat-fish consists of the compressed tail. These fishes have no air-bladder, and they seem to have little power of rising from the bottom. When disturbed, they will raise themselves into a vertical position, so as to show their white sides; and they then dart along with great rapidity ; but they soon return to their usual posture, and glide along with a sort of undulating motion, at a little distance from the bottom. The Flat-fishes are very tenacious of life ; and the flesh of all of them is very palatable. That of the Turbot is considered as the most delicate afforded by any marine fish. Although most of the species are exclusively marine, yet the Flounder and some others occasion- ally ascend rivers, and thrive in brackish, or even in quite fresh water. The Plaice, Flounder^ Turbot, Dab, Fluke, Brill, Sole] and other well-known fish of this family, are closely allied to each other, both in structure and habits ; and they are all in- habitants of British seas. The Halibut, also an inhabitant of the Northern- seas, is larger than any one of these, attaining a length of six or seven feet, and a weight of 400 or 500 Ibs. Its flesh is rather coarse and dry, but it admits of being salted. In some of the Mediterranean species, the eyes look towards the left side, instead of towards the right; the latter, though the ordinary rule of the family, is sometimes departed from in other species ; the individuals that exhibit the unusual formation being said to be " reversed." As an instance of the extent and im- portance of the Fisheries, of which this family is the object, it may be mentioned that the Dutch draw about 30,0001. per annum for the supply of Turbot alone to the London market ; and it is estimated that, of the whole quantity brought to Billingsgate, the Dutch is not more than one-fourth. 629. The Apodal species, or those in which the ventral fins 68 AMMODYTIDJE. — SILURID.E. are wanting, are generally of an elongated form, somewhat re- sembling that of the Eels, with which indeed they were arranged by Cuvier. They may be readily distinguished from the Eels, however, by the freedom of their opercula ; these in the Eels are confined by the skin in such a way as only to leave a small aper- ture.— In the AMMODYTIDJE, or Sand-lances, the caudal fin is distinct and forked ; and the skin, which is naked, is of a beauti- ful silvery lustre. They are small Fishes which frequent our coasts, burying themselves in the sand to a depth of six or seven inches during the time that it is left dry by the ebb tide. They are used as baits by the fishermen, who drag them out of the sand by means of iron hooks and rakes. — The OPHIDIID^E are still more Eel-like in their appearance ; their perpendicular fins forming a continuous border round the posterior extremity of the body. They are sometimes destitute of pectoral fins. Two or three species have been taken on the British coasts, but most of them inhabit the Mediterranean ; none attain a large size. F. — PHYSOSTOMI. 630. In this, the last group of the Bony Fishes, the air-blad- der is connected with the pharynx by a sort of duct, a character which only occurs elsewhere amongst the Ganoidei. Their fins are always supported by soft rays, but in some cases the first ray of the dorsal, anal, and pectoral fins is spinous. The ventral fins, when present, are always situated on the abdomen. This group includes nearly the. whole of our fresh-water Fish, and an im- mense number of species which inhabit the seas ; some of the latter are of the highest importance to Man. 63 1 . The first family is that of the SILURID^E, or the Silures, distinguished by the want of scales ; the skin is naked, but fre- quently has bony plates imbedded in it. The mouth is surround- ed by tentacles ; the first ray of the pectoral fin is very strong and bony, and the Fish can, at pleasure, lay it flat on the body, or keep it fixed in a perpendicular direction, in which case it becomes a formidable weapon, capable of inflicting very trouble- SILURID.E. — CYPRINIDJS; CARP. 69 some wounds. There is, however, no sufficient reason to believe that these are venomous. A singular point in the organisation of these Fishes consists in the existence of a chain of small bones connecting the air-bladder with the ear. In many cases the se- cond dorsal fin exhibits tht adipose structure characteristic of the Salmon family. The Siluridae inhabit the fresh waters, and are generally confined to warm climates. The common Silure, however, is a native of Europe, and occurs abundantly in some of the large rivers of the continent. It is a large Fish, measur- ing from six to eight feet in length. — The Malapterurus, remark- able for its electrical powers, has been already noticed (§ 563). 631*. The CTPRINID^E, or Carps, have the mouth small, and the jaws toothless ; but the pharyngeal bones are armed with strong teeth, which work against some horny plates supported upon a process of the lower part of the skull. The body is clothed with scales of variable size ; the dorsal fin is single, and the air-bladder, which is divided into two parts by a constriction, is connected with the ear, as in the Siluridce, by a series of small bones. They are inhabitants of the fresh waters, and. are exceed- ingly numerous both in species and individuals, and appear to be distributed over most parts of the world. They feed upon aquatic plants, worms, and insects ; the plants constituting their principal diet during the summer, when their flesh is very indif- ferent. A few of them also feed upon small Fishes. The com- mon Carp does not appear to be a native of this country, but to FIG. 3.i3.— HARBEL. have been introduced from the South of Europe ; it thrives very well, however, in the most sluggish parts of rivers, and still bet- 70 BARBEL, ETC. — ANABLEPS. — ESCCID.E. ter in ponds, sometimes attaining the length of four feet. The beautiful little Gold and Silver Fish belong to a small species of Carp, which is very much disposed to pass into varieties. — The Barbel is another well-known large species, which sometimes attains the length of three feet ; ifr inhabits rivers, and is only found in those which have a connexion with the sea. It keeps at the bottom of the water, working in the sand or mud with its snout in search of insects and worms. — The Gudgeon, Tench) Bream, Roach, Chub, Dace, Bleak, and Minnow, which are all well-known pond and river Fishes, belong to this family, as does also the Loach, which passes the cold weather buried in the mud. 632. Nearly allied to the Carps are the P.ECILIID^E, in which the jaws are armed with numerous small teeth ; the air-bladder is simple, and the chain of bones uniting it with the ear is wanting. They are small fishes, inhabiting the fresh waters of hot coun- tries. A few of them are viviparous. — The Anableps, or Four- eyed Loach, belonging to this family, is remarkable for being apparently possessed of four eyes. This is not, however, really the case ; for although the cornea and iris are divided by trans- verse bands, so that there are two pupils on each side (ANIM. PHYSIOL. § 533), yet the other parts of the eye are single. This is one of the viviparous species. — Another small family, that of the CHARACINID^E, seems to unite the Carps to the Salmonidae ; like the latter, they have an adipose dorsal fin, and teeth in the jaws ; but the air-bladder is divided into two parts, and furnish- ed with a series of bones, as in the Carps ; and some other pecu- liarities of internal structure indicate their affinity to those Fishes. They are found in the fresh waters of tropical countries, and some of them are of considerable size and very voracious. 633. The family of the ESOCID^E, or Pikes, is nearly allied to the Cyprinida% but differs in having the jaws and palate armed with a formidable ar- rangement of teeth, and in the FIG. 384 .-PIKE. . . ,, . 1 . , , position ot the dorsal and anal fins, which are placed very far back on the elongated body. All the known species are inhabitants of the fresh waters of tern- PIKE.— MORMYRID.E.— SALMONID^E. 71 perate countries. The common Pike is well known as being one of the most voracious and destructive of all the smaller Fishes. M. Jesse mentions that eight Pikes, of about 5 Ibs. weight each, consumed nearly eight hundred Gudgeons in three weeks ; and that one of these devoured five Roach, each about four inches in length, within a quarter of an hour. The Pike not only makes havoc among other Fish, but will devour frogs, water-rats, field- mice, and the smaller aquatic birds ; and instances are on record iu which it has even attacked Man. It grows rapidly, and often attains a weight of thirty or forty pounds. It also appears to be very long-lived, having been known to attain the age of ninety years, and having in one instance (there is reason to believe) lived to the patriarchal age of 267 years, and attained the enormous length of nineteen feet. — The MORMYRID^E, a small family nearly allied to the Pikes, are distinguished from all the other bony Fishes by the amalgamation of the intermaxillary bones. They have the head covered with a thick naked skin, which closes the opercula, with the exception of a small perpendicular slit. They are found in the Nile and Senegal, and their flesh is said to be excellent. 634. In the SALMONID.E, or Salmons, all the rays of the first dorsal fin are soft or jointed ; and the second dorsal is entirely adipose, being merely a fold of skin inclosing fat. The species of this family are at once distinguished from the SiluridsE, in which an adipose fin sometimes occurs, by having the body co- vered with scales ; they are generally very muscular, and pos- sessed of great strength ; and they are voracious in their habits, feeding rather upon Insects, small Crustacea, &c., than upon other Fishes, The different subdivisions of the group vary con- siderably in regard to the position of the fins, and the degree in which the mouth is armed with teeth. Most of them frequent the estuaries of rivers, and ascend the stream at regular periods to deposit their spawn in its higher parts ; and it has been ascer- tained that the same fish and their descendants resort in suc- cessive years to one particular locality. Nearly all the members of the family are clouded with transverse dusky patches when very young, and undergo considerable changes in their livery 72 SALMON; TROUT; SMELT. before they arrive at their full growth. Hence there is much difficulty in determining their species; which is increased by the circumstance, that the male, in many instances, appears to be capable of propagation long before arriving at its full growth. The Salmon of our own rivers is one of the largest of the whole family ; but in consequence of the eagerness with which it is pursued by fishermen, it does not often attain its -full size in this country. Enormous specimens, however, are now and then captured ; a weight of 40 Ibs. does not seem very uncommon ; and in 1821, a specimen was exhibited in London, weighing 83 Ibs. The usual time at which the Salmon leaves the sea, is the autumn ; it remains in the rivers during the winter ; and returns to the sea, after having deposited the spawn, in the spring. The young fry, termed Smalts, are carried down to the sea in the montHa. of April and May. In some rivers, however, they do not make their ascent until the winter ; and in others they even delay it until the spring. These variations appear to depend upon differences of temperature in the rivers themselves ; since, when these are very cold, the fish avoid pass-ing the win- ter in them. Before depositing its spawn, the Salmon makes a furrow with its nose in the gravelly bed of the river; and its eggs, when deposited in this, are carefully covered up. The common Trout is entirely a fresh-water fish, delighting in rivers which have a rapid current, and abounding also in many stream- fed lakes ; it lurks during the day in the deep pools, under the shadow of large stones, or under precipitous banks ; and becomes active towards evening, when it begins eagerly to pursue its prey, which seems to consist especially of Insects and aquatic Larvse, and of small Crustacea, — but also of small fishes, and the ova of the larger ones. — The Char is considered as having the most delicate flavour of any of the fishes of this family ; it is a lake fish, and is not very common in this country. — The Smelt resembles the Salmon in its habits, but is much smaller ; it has been found, however, to thrive very well when confined to fresh water. — Several other genera exist in various parts of the world ; some of them approach other families in their general structure and are exclusively marine in their habits. A few curious ma- CLUPEID^ ;— HERRING, PILCHARD, &C. /3 rine Fishes, nearly allied to the Salmons, constitute the family SCOPELID^E. They differ from the Salmonidae in the structure of the upper jaw, and also in the absence of an air-bladder. 635. The family of CLUPEID^E, or Herrings, and their allies is one of the highest importance to man. These have a scaly body like the Salmon's, but no adipose dorsal fin ; and there is also a difference in the arrangement of the bones of the jaws. They are for the most part marine fishes ; only a few species, as the Shad and White Bait, ascending rivers periodically like the Salmon. The habits of the common Herring, in regard to its reputed migrations, have been already noticed (§ 566) ; not- withstanding the very circumstantial account given by Pennant, and copied by later authors, it seems now to be well established that the only migration of the Herring is from the deep seas to the shores at the spawning season, and from the shores to the deep seas when this is over. It is a curious and perplexing cir- cumstance that the shoals of Herrings do not continue to resort to the same localities ; but that they will leave some parts of the 'coast which they had been accustomed to visit with regularity, and make their appearance on others which they bad not pre- viously frequented. Their food consists of small Crustacea and Fishes ; and it appears tjiat they do not spare the young of their own race*, five small Herrings having been found in the stomach of a large female. They usually swim near the surface of the water ; and, like other fishes whose habit is the same, their gill- openings are large, their respiration considerable in amount, their muscular energy great, and their demand for oxygen so constant, that, when taken out of the water, they speedily die. The Pilchard, Sprat, Shad, White-Bait, Sardine, and Anchovy are all more or less closely allied to the Herring, — the last de- parting from it most widely. The range of the Pil- chard, which abounds on the FIG. 385.— ANCHOVY. r* • -\ Cornish coast, is more southern than that of the Herring ; and the Anchovy and 74 HERRING AND PILCHARD FISHERIES. Sardine replace the Herring in the Mediterranean, where it is unknown. The importance of the Herring and Pilchard Fisheries is very great. Some notion of it may be formed from the fact, that more than 500,000 barrels of herrings only have been cured in one year; of which more than half were exported. The num- ber of persons to whom this Fishery gives employment in various ways must, therefore, be very considerable, though it cannot be exactly estimated ; and the value of the product as an article of export trade is very important. The total number of persons directly employed in the Cod and Herring fisheries of Britain, as Fishermen, Coopers, Curers, &c., was nearly 87,000 in the year 1836. Of the extent of the Pilchard fishery some idea may be formed from the fact, that about 12,000,000 of these fish have been sold for home consumption alone in a single year ; and it is said that more than this number have been brought into one port in a single day. The average produce of the Cornish Pilchard Fisheries is said to be no less than 60,000,000 of fish. The principal centre of the Herring fishery is at Yarmouth in Nor- folk ; that of the Pilchard fishery is the neighbourhood of the Land's End. 636. In the remainder of the Physostomi the ventral fins are entirely wanting. These are at once^ known by their long, slender, snake-like bodies, covered with a soft skin, and having the scales very minute, and often almost invisible. The gill- orifices are very small, and are prolonged far back, so that a sort of long passage is formed from the branchial chamber to the sur- face of the body. In this manner the gills are so much sheltered, that the fish can remain out of the water for a considerable time, without those organs being rendered unfit (by becoming dry) to carry on the respiration. Of course, the access of water to the gills cannot at any time be so free as it is in fishes with large gill-openings ; and their respiration may be habitually less. It is in animals with a feeble respiration, as has been already re- marked in the case of Reptiles, that we find the greatest tenacity of life ; and every one knows the difficulty with which the Eel is killed — the most cruel injuries being sustained by it without the loss of its vitality. MUR.ENIDJE, OR EEL-TRIBE. — GTMNOTID.E. 75 637. In the MURJENID^E, or True EeJs, the upper jaw is formed solely of the intermaxillary bones, and the branchial apertures are placed on the side of the head. The ordinary Eels, of which there are several species, inhabit ponds, rivers, and the brackish water at the mouths of rivers. In the autumn they make their way to the sea in vast numbers ; for the purpose, it is be- lieved, of depositing their spawn. Myriads of minute Eels, three or four inches long, are seen in the spring, making their way up rivers, and dispersing into the tributary streams as they proceed ; but whether the parent Eels thus return is un- certain. It is well known that the Eels which inhabit inland lakes and ponds, whence they cannot escape to the sea, are able to breed without this migration ; but it appears that their season is somewhafc later, the water in such situations being colder than that of the sea in the early spring. Eels frequently quit the water, in warm, damp nights, and wander over the grass ; either in quest of worms, frogs, or other food ; or in order to change their locality. — Many of this family are chiefly marine ; though they occasionally stray into the mouths of rivers ; this is the case, for instance, with the Conger, which is one of the largest of the whole group, sometimes measuring six feet in length, and being as thick as a man's leg. — The Ophisurus, or Snake Eel (so called from its strong resemblance to a serpent) of the Medi- terranean, attains the same length, but is not so thick. In the genus Murcena, and its allies, the pectoral as well as the ventral fins are wanting; and the gill-openings are extremely small. This, too, is a Mediterranean fish ; it was much esteemed by the ancients, who kept it carefully in ponds ; and there is a well- known story of a cruel master, who caused his offending slaves to be flung alive into the ponds, to feed the Muraenae. The com- mon species grows to the length of three feet or more ; its sur- face is mottled brown and yellow ; and it is very voracious and 638. The GYMNOTIDJE, or Electric Eels, have been separated from the preceding family on account of the less complete in- closure of the gill-covers by the skin, and the structure of the upper jaw, which is partly formed by the maxillary bones. The 76 ELECTRIC EEL. — ORDER CYCLOSTOMI. electric powers of the Gymnotus have been already mentioned (§ 560) ; the other species of the family, of which a considerable number inhabit the fresh waters of South America, appear to be destitute of any electrical properties. The last family is that of the SYMBRANCHUXE, in which the gill-passages unite, so as to open externally by a single orifice on the lower surface of the neck ; this is sometimes divided by a longitudinal partition. Like the Gymnotidae, they are inhabitants of the fresh waters, and are confined to tropical climates. With these we close the long series of the bony Fishes. ORDER IV.— CYCLOSTOMI. . 639. The Fishes of this Order exhibit a very imperfect structure of the skeleton. So far are they from having a jointed vertebral column, that this is replaced, in the highest among them, by a sort of cylinder of cartilage, which represents the bodies of the vertebrae, but which does not show any definite division into segments. There are no ribs, nor are there either pectoral or ventral fins ; there is, in some, however, a kind of fin beneath the tail, but this has no rays. The body is usually elongated, and nearly cylindrical ; and terminated by a circular mouth adapted for sucking. The branchial organs form little sacs, on the walls of which the blood-vessels ramify. 640. In the PETROMYZONID^, or Lampreys, there are seven gill-openings on each side ; there are strong teeth in the ring of the mouth ; and the inner part of the disc, which may be con- sidered as the lip, is also beset with hard tooth-like tubercles. FIG. 386 — LAMPREY. The tongue, which moves backwards and forwards like a piston. PETROMYZONID.E MYXINID-E. 77 and which is the principal instrument in the act of suction, is also furnished with two longitudinal rows of small teeth. By means of this sucker, the Lamprey is said to attach itself to the bodies of the largest fishes, so as speedily to pierce through their integuments, and prey upon their substance. It seems far more probable, however, that the Lampreys feed entirely upon small aquatic animals. The largest species, which attain the length of two or three feet, are marine ; the smaller, which chiefly in- habit rivers, are sometimes called Lamperns. According to some recent researches of Dr. August Miiller, the young of the Lam- preys are very different in structure from their parents, being in fact the Fishes described by Ichthyologists as forming the distinct genus Ammoccetes. The most singular circumstance revealed by his observations is that the Ammoccetes do not gra- dually acquire the mature characters during their growth, but first attain the full size of the adult Lamprey, and then pass through a rapid change, so as to resemble the larvae of Insects. 641. The members of the family MYXINIDJE, or Hags, have not even a cartilaginous ring around the mouth, its borders being entirely membranous, and furnished with only one tooth. The mouth is surrounded by eight cirrhi, or tendril-like feelers ; which remind us of the arms of the Cuttle-fish in miniature. This fish is destitute of eyes ; and does not seem, indeed, to have any other special organ of sensation than these cirrhi. The commonest species is known to British fishermen under the name of the Hag; it is found in the interior of other fishes, whose bodies it has entered for the purpose of devouring them ; and it seems to attack in preference those which have been hooked, and which, consequently, are not able to defend themselves. As many as six Hags have been found in the skin of a single Had- dock on the Norway coast (where this species is more abund- ant than on our own), the flesh of which they had almost entirely consumed. It is usually from twelve to fifteen inches in length, and of the thickness of the little finger ; and its whole tissues are so soft, that it would not have been supposed capable of in- flicting any serious injury. The quantity of mucus which it can secrete from its surface is enormous ; it has been asserted, that 78 ORDER LEPTOCARDII. if a Hag be placed in a pitcher of sea-water, it will speedily convert this into a semi-transparent jelly ; and that, if placed in a fresh quantity of water, it will change this in the same manner. ORDER V.— LEPTOCARDII. , 642. The most imperfectly formed of all Fishes is undoubt- edly the Amphioxus, or Lancelot, which of itself forms the last order of Fishes. It has even by many naturalists been removed altogether from the Vertebrated sub-kingdom, on account of the almost complete absence of what are usually regarded as the distinguishing peculiarities of that group. Nevertheless, an at- tentive examination of its structure shows, that it bears a closer resemblance to the true Fishes than to any other animals — ex- hibiting their conformation in (as it were) a degraded form. It is of very diminutive size, scarcely an inch in length, very slender, and almost transparent. The body is compressed later- ally ; and there are no pectoral, ventral, anal, or caudal fins, but only a narrow membranous border which runs along the whole of the dorsal and a part of the ventral surface, and expands at the tail into a lancet-shaped fin. There are no eyes, nor any vestige of any external organ, except the mouth, which is surrounded by very small cartilaginous points. There is scarcely any trace of a vertebral column, or of ribs ; 'yet the muscles are arranged with great regularity, on the plan of those of Fishes in general. The mouth leads into a large branchial cavity, in which currents are produced in the water by the action of cilia ; the entrance to the intestinal canal is at the back of this cavity, and the food is no doubt conducted to it by ciliary action. One of the most curious parts of its structure is the complete absence of cerebral hemispheres, and even of ganglia of special sense ; the spinal cord being, apparently, the only centre of its nervous system. Thus it may be characterised as one of those " experiments pre- pared for us by Nature;" exhibiting to us a case, in which the Cerebrum is never developed ; the phenomena of which closely FOSSIL FISHES; CLASSIFICATION. 79 correspond with the results that have been obtained by the arti- ficial removal of that organ. ( ANIM. PHYSIOL. § 465.) The heart also is entirely deficient, and the blood, like that of the Inverte- brate animals, is colourless. 643. The Geological distribution of this class presents many points of the greatest interest. As might have been anticipated from what is known of the history of the production of the present crust of the globe, we find remains of Fishes in the earliest formations, which distinctly exhibit the action of water, — that is, which were deposited as sediments in the bed of the ocean ; and this probably long before any land animals existed upon the surface of the globe. But the Fishes of this early date were, for the most part, formed upon a very different plan from those of the present epoch, so that there are very few of those now existing which bear any close resemblance to them ; whilst, on the other hand, the greater proportion of the species now exist- ing had no representatives among those which inhabited the primeval ocean. Many of the latter are known to us only by their scaly coverings, which are frequently preserved with the greatest perfection, when the internal skeleton has disappeared, — the scales having the hardness of bone or even of enamel, whilst the skeleton was cartilaginous. — As we ascend towards the newer formations, we find the character of the class gradu- ally changing, — the forms, which were predominant in the older rocks, disappearing one after another, and being replaced by others, which bear more resemblance to those now existing. It has been discovered by Professor Agassiz, that there is a general correspondence between the character of the scales and the in- ternal organisation of the fish ; and he has proposed that the arrangement of the class shall be founded in the first instance upon the form and structure of the Scales. This classification has not been accepted by Naturalists, but the advantages which it presents, in regard to the study of Fossil Fishes, give it a claim to our attention. — According to Professor Agassiz, all Fishes may be arranged under the four following groups : I. GANOIDIANS ; from the Greek yavoe, splendour. — The Fishes of this order are covered by scales or plates, composed 80 CLASSIFICATION OF FOSSIL FISH. internally of bone,4 and coated with enamel. The scales are regularly arranged, and entirely cover the skin with an almost impenetrable armour. — The Sturgeons and the Lepidosteus are almost the only living representatives of this order. II. PLACOIDIANS; from the Greek 7r\a£, a broad plate. This order contains Fish whose skin is covered irregularly with plates of dentine, often, of considerable dimensions, but sometimes reduced to small points. — Among existing Fish, this order com- prehends only the Sharks and Rays and their allies. The two preceding Orders are also characterised by the un- symmetrical tail ; which is now confined to the Sturgeons, the Sharks and Rays, and the Lepidosteus. III. CTENOIDIANS ; from the Greek KTELQ (genitive Krevog), a comb. The Ctenoid Fish are covered with horny or bony scales, jagged like the teeth of a comb on the outer edge. The Perch and many other existing genera are examples of this order, which contains but few fossil forms. IV. CTCLOIDIANS ; from the Greek KVK\OG, a circle. — The Fish of this last order have their scales smooth and simple at the margin, and often ornamented at the upper surface. The Her- ring, Salmon, &c., are referred to the Cycloid order ; which, with the preceding, includes the majority of the existing species. 644. Now the Fish of the oldest or Palceozoic strata belong almost exclusively to the^r^ of these divisions ; and an immense number of Ganoid Fish, forming several families, are exclusively met with in the Old Red Sandstone formation. Many of the forms presented by these are most extraordinary, — being totally unlike any with which we are acquainted among existing species, — and indicate an apparent mixture of the characters of the class of Fish with those of the Crustacea. Indeed as to the real nature of some of the species, even Agassiz was at first undecided, — so strong was the resemblance presented by them to certain forms of Crustacea, especially the Trilobites hereafter to be described ; and it was not until connecting links were dis- covered, that the nature of them could be certainly determined. The head and body of many of these Fish were covered by large hard plates; whilst the internal skeleton, from the GANOID FISHES OF OLD KKD SANDSTONE. *<)!) entire absence of any remains of it, seems to have been composed of soft cartilage. In the Cophalaspis (or buckler-head), the head was very large in proportion to the body, occupying one-third of its length, and being rendered of enormous breadth by two cres- cent-shaped wings, extending backwards and outwards. In the Ptericthys (or winged fish), the plates both of the head and body were very large, and consequently few in number ; it was fur- nished with a pair of wing-like fins, placed far forwards, and terminating in a kind of hook, or strong curved point ; and the tail, which occupied more than a third of the total length of the animal, was straight, pointed, and covered with small tubercu- lated angular scales. " Most probably the tail was employed as the principal organ of locomotion ; the pointed fins being elevated at the approach of danger, and the animal in this way rendering itself as unapproachable and as difficult to be swallowed as its form would admit of." The Cocosteus had a body of triangular shape, tapering away towards the tail ; and was covered almost entirely by a central plate, much larger than any of the others, having a continuous ridge along the middle of the back ; it was also furnished with a couple of defensive fins, situated near the head, like those of the Ptericthys. The tail evidently possessed a vertebrated structure ; and it was by this that the animal was most certainly recognised as a Fish, — its jaws and teeth having more the characters of the nippers of a Lobster or the mandibles of a Beetle. The teeth were chiselled, as it were, out of the solid bone of the jaw ; just as the teeth of a saw are cut out of a plate of steel : and the line of opening of the jaws was vertical, as in the Articulata, instead of being horizontal^ as in the Verte- brata. Remains of this fish are found very abundantly in some situations ; varying from a few inches to two feet in length. — The other Fishes of the Palaeozoic epoch were, for the most part, less widely different from those of the present day ; one remark- able genus may be mentioned, the Holoptychius, which exceeded most of the others in size, and was evidently adapted to prey upon them. The name of this fish is derived from the large undulating furrows marked upon the surface of its enamelled scales, which give them a most beautiful appearance ; these scales, VOL. II. G 70* SAUROID FISHES. by their strength and magnitude, seem as if they might have served for the armour of a Crocodile ten times the size of the fish. Its head, also, was inclosed within bony plates, whose upper surface was covered with rough tubercles of enamel ; and the jaws, likewise, were composed of bone, whose outer surface was polished, covered with enamel, and unclothed with skin. A row of thickly-set pointed teeth fringed the enamelled edges of the mouth, and corresponded to the lips of ordinary fish ; whilst within this was a second and wider range of teeth, at least twenty times the bulk of the others. This, and some other allied genera, were evidently the "pirates" of their day ; the extraordinary armature of their jaws being in conformity with the remarkable defences, with which the bodies of the fishes that served for their prey were endowed. 645. As we pass from the Old Red Sandstone into the newer rocks, we meet with a change in the characters of the Fish, whose remains are imbedded in them. All those just described, with the exception of the last, disappear ; and they are replaced by others. Still we find that of the Fish contained in the Mountain Limestone and the beds associated with it, a large proportion belonged to the order Ganoidians ; but, among these, the Sauroid fishes now predominate. These are at once dis- tinguished by the peculiar form of their teeth ; which are marked by longitudinal furrows like those of Crocodiles ; and which have a conical hollow at the base, in which the next tooth is prepared, as in. many Reptiles. So strong, indeed, is the resemblance of both the teeth and scales of several of the Fishes of this group to those of some Crocodilian animals, that, when first discovered, they were immediately referred to that class. The dimensions of the teeth of the genus Megalic- thys (large fish), far exceed those of any other fishes' teeth that have been yet examined ; one of them having been found to measure nearly four inches in length, with a breadth at the base of nearly two inches. The large teeth are accompanied by several very small ones, which alternated with them, and were distributed over the whole of the inside of the mouth. Scales of this fish have been met with as much as five inches in diameter. .meter. PLACOID FISHES OF CARBONIFEROUS SERIES. There is some reason to think, from the character of the other fossils with which its remains are associated, that tins Fish was an inhabitant of fresh water, like the comparatively diminutive Lepidosteus of the present day (§ 572). The Sauroid fishes pre- dominate in an increasing degree among the genera of the Ganoid order, as we rise through the newer strata ; and at last they become the only representatives of that order. It is between the Oolitic and Chalk periods, that we find the most remarkable change in the proportion which the Fishes of this group bear to those of other orders ; for, whilst the Oolite includes the remains of numerous fishes of the Ganoid order, — many of them Sauroid fishes of great size and strength, — we find but very few in the Chalk and later formations, and even these are of diminished size and ferocity; so that, by this gradual change, the order has now become nearly extinct, as already mentioned. 646. It is in the strata of the Carboniferous order, or the Mountain Limestone and the overlying beds of the Coal series, that we encounter the first appearance, in any considerable proportion, of the Fishes of the Second order, or Placoidians. These do not depart so widely from the forms with which we are familiar at the present day, as did the earlier Ganoidian Fishes ; but it is interesting to remark, that the greater number of the early Placoidians did not bear a resemblance to the Sharks and Rays which are most abundant at the present time, but to some that are now regarded as aberrant forms, separated from the rest by peculiarities of conformation. This is the case, for example, with the Cestracion Philippi, or Port-Jackson Shark ; which has the margins and inner surface of the jaws covered with flat pavement-like teeth, disposed in an oblique row ; whilst the front of the mouth is armed with sharp, angular, and pointed teeth, more resembling those of the ordinary Sharks. The latter are evidently adapted for seizing and retaining the food ; the former for crushing and bruising it. These teeth an: rarely found connected together in a fossil state. Now, of the fossil Fishes presenting these peculiarities, and referred on that account to the family Cestracionts, remains are found even in the 72* PLACOID, CTENOID, AND CYCLOID FISHES. Palaeozoic strata; they become more numerous in the Car- boniferous series ; they are very numerous in the Lias and Chalk formations ; but there they cease almost entirely, — the strata of the Tertiary series scarcely containing any of them, and the Port-Jackson Shark being the only representative of this family at the present day. — Intermediate between these and the ordinary Sharks was another family, to which the name of Hybodonts has been given. The teeth of this division were stronger and blunter than those of the true Sharks, but were not so much flattened as those of the Cestracionts ; and they seem to have been adapted for cutting, tearing, and bruising substances of considerable hardness. The Fishes of this family seem to have made their first appearance in the later part of the Coal forma- tions ; they were very abundant during the Oolitic period ; but ceased entirely at the commencement of the Chalk deposit. — Lastly, the ordinary Sharks, constituting the Squaloid family, which are distinguished by their sharp lancet-like teeth, have no representatives among the Fossil Fishes of older date ; but their remains are first found in the Chalk formations, and extend through all the newer strata down to the present time. — The Rays, also, of the earlier periods had teeth more flattened than those of later epochs ; and we find from their fossil remains, that some of the forms, which are now regarded as exceptional or aberrant, were formerly more abundant. Thus of the Myliobatis or Eagle-Ray (§ 584), of which five species are at present known, fifteen fossil species have been discovered. 647. The Ctenoid and Cycloid Fishes make their first appearance in the Chalk formation ; when all the previously- existing genera of the Ganoid and Placoid orders had become extinct, and when the new ones that were brought into existence were (as we have seen) far less numerous than before. There is, then, a sort of boundary line at the base of the Cretaceous or Chalk deposits, which divides the class of Fishes in a most remarkable manner ; — all those below that line, in the order of the strata, or (in other words) all those which existed at a period anterior to the deposition of the Chalk, having belonged to the two first orders, those with enamelled scales; — whilst by far the OEN'ERAL RELATIONS OP FOSSIL FISHES. *73 larger proportion of those existing at a subsequent time, as at the present epoch, belong to the two orders with horny scale?, which comprehend at least three-fourths of the 8000 living species of Fishes known to Naturalists. Of the fossils of these last orders, which abound in the formations of the Tertiary period, it is sufficient to say, that they may nearly all be referred to families which have been described as now existing ; that many of them belong to the same genera with recent Fishes ; but that it is doubtful if any of them are of the Baroe«JMCUl with those now tenanting our seas. 648. The sketch here given of the principal groups of Fossil Fishes, is sufficient to illustrate some very interesting points in the history of this class. In the first place, we see that the first- created Vertebrated animals so far resembled the Invertebrated classes, as to possess a very dense externa'l skeleton ; whilst their internal skeleton was so soft, as not to be capable of being pre- served ; and it appears to have been to the Crustacea, which are among the highest of the Articulated series, that these Fishes were most nearly related. On the other hand, among the Fishes of the present time, the Cyclostomata, which present the cha- racters of the Vertebrata in their most imperfect form (§ 585), •are rather analogous to the Annelida, or Worm tribe ; with which, indeed, some of them were actually classed by Linnaeus. — We may next observe, that the covering of dense enamelled scales, in which all the Fishes of the earlier formations were inclosed, rendered necessary a peculiar conformation in the mouths of those, which were destined to prey upon them and to restrain their multiplication. Thus we find the mouths of the predaceous Ganoid fishes, such as the Holiptychius and its allies, and in those of the Cestracionts and Hybodonts, a pavement-like cover- ing of flat enamelled teeth, adapted to crush the hardest sub- stances. But when the enamelled-scaled Fishes had given place to those furnished with a softer covering, we find these enamelled pavements of the jaws replaced by sharp cutting teeth, — the predaceous Ganoids disappearing altogether, and the Cestracionts and Hybodonts giving place to the Sharks. — What was the purpose for which all the earlier races of Fishes were provided 74' GENERAL RELATIONS OP FOSSIL FISHES. with the enamelled covering so often alluded to, and why these races should have given place at a later period to others so differ- ently constituted, we have no certain means of knowing. It has been suggested by Dr. Buckland, that the purpose of this cuirass may have been, to defend the bodies of the animals against waters that were warmer, or subject to more sudden changes of tem- perature than could be endured by animals, whose skin was pro- tected only by such thin and often disconnected coverings, as the membranous and horny scales of most modern Fishes. Such changes of temperature were more frequent, there is good reason to believe, in the earlier epochs of the Earth's history, than they are at the present time. 649. It may be further remarked, that the history of the Fossil Fishes most clearly proves, that the first-created forms of Animal life were not the least perfect, — as some have maintained ; and that there is not a regular succession of new races, increasing in elaborateness of structure, from the oldest to the most recent formations. For among the earliest races of Fishes, we find that those of the Sauroid family, which had many characters of eleva- tion, held a conspicuous place ; and that, when these were replaced by the class of Reptiles, which was called into existence as soon as there was any land for its habitation, they ceased to* exist, and were succeeded by races of Fishes which must be regarded as lower in the scale. 75' CHAPTER VIII. GENERAL CHARACTERS OF ARTICULATED ANIMALS. 650. THE animals of which is composed the Sub-Kingdom ARTICULATA, not only present an internal structure which is essentially different from that of the other three divisions of the Animal series, hut are likewise distinguished by external charac- ters, which are usually so definite and evident, that they may be almost always recognised at the first glance. Their entire body, in fact, is divided (more or less obviously) into segments ; and seems to he composed of a series of rings placed in a line. In some Articulated animals, this annular (ring-like) appearance results merely from a certain number of transverse folds, which furrow the skin, and encircle the body ; but in the greater num- ber, the animal is enclosed in a sort of solid armour, composed FIG. 387-— IULUS. of a series of rings, united one to another in such a manner as to allow them a certain degree of movement. This envelope has uses analogous to that of the internal framework of Vertebrated animals ; for it determines the general form of the body ; it protects the soft parts; it gives points of attachment to the muscles ; and furnishes them with levers, by their action on which the movements may be effected with precision and rapidity. Hence it may be termed an external skeleton. It must be borne in mind, however, that the hard substance of which it is composed has no analogy in structure, or in 76* GENERAL STRUCTURE OP ARTICULATED ANIMALS. mode of growth, with the bones of Vertebrated animals. It con- sists, in fact, of the skin, consolidated by the deposition of horny or calcareous matter in its substance ; and instead of being able to grow in all directions in the manner of bone, it undergoes very little change when it is once fully formed, and it cannot Jbe made to increase in size except by addition to its edges. 651. The different rings, or segments, of the body of an Arti- culated animal, always bear a strong resemblance to each other ; and sometimes, as in the lulus (Fig. 387), and the Scolopendra, or Centipede, they seem like actual repetitions of each other. Dorsal arch Dorsal oar Dorsal member I Ventral member Ventral arch Ventral oar FIG. 388 VERTICAL SECTION OF A SEGMENT OF AN ANNELIDE, BELONGING TO THE GENUS AMPHINOME. Each ring may bear two pairs of appendages, or members ; the one belonging to its dorsal arch, or the upper part of the seg- ment ; whilst the other belongs to the ventral arch, or the under part of the ring. In those Articulata in which the principle of "division of labour " does not yet manifest itself, — that is, in whose bodies we find a number of similar parts adapted to perform the same functions, instead of an assemblage of dif- ferent parts, constructed each for its own special purpose, — all the segments are provided with these appendages, and their number is sometimes extremely great. But in all the higher tribes, we find the appendages of certain segments attaining a high de- gree of development ; whilst, by a sort of compensating principle, the others present themselves 'as mere rudiments, or are not even at all discoverable. In general the appendages of the ventral arch are alone developed ; and the variety of forms which they APPENDAGES OF THE TRUNK. *77 present is greater, in proportion as the animal is more elevated in the scale. Thus we find them so modified as to become antenna, — those long, horn -like filaments, with which the head is furnished in Insects and Crustacea, — or to be subservient to mastication by being converted into jaws, or to take the form of legs, swimming organs, &c. Of this metamorphosis we shall hereafter notice some remarkable examples in the class Crus- tacea. Sometimes, the appendages of the dorsal arch are present throughout, and perform, like those of the ventral arch, the functions of limbs ; of this we find many examples amongst the Annelida. But in general, no more than two pairs pre- sent themselves ; these are situated on the segments constituting the centre of the body ; and they perform the functions of wings or of analogous organs ; as we shall hereafter see, when speak- ing of the class of Insects. The legs are generally 6, 8, 10, or 14 in number ; sometimes many hundreds may be counted ; and sometimes they are altogether deficient ; but when they exist at all, they are never fewer than six, which is the number that is characteristic of the class of Insects. Sometimes instead of distinct legs, we meet with strong bristly appendages, as in the Earth-worm ; or bundles of such bristles, in the midst of which one is occasionally a cirrhus or tendril-like appendage, constitut- ing a sort of rudimentary leg, as in many Annelida (Fig. 388.) 652. The tendency to'repetition ex- hibited by the segments of the body, is as remarkable in the disposition of the muscles and of the nervous system, as it is in the arrangement of the general envelope. In ffisophagu8 . Ct crop . d, &z. chylific stomach ; and the other *arA ; *> chylific stomach ; /, small intes- tine ; g, rectum ; h, biliary vessels. extremity is sometimes free, but sometimes fixed to the intestine, either near the first opening CIRCULATION IN INSECTS. 101 or close to the rectum. Lastly we find, towards the extremity of the intestinal canal, other secreting organs, that serve to elaborate particular liquids (such as the poison of the Bee's sting), which several Insects can throw out from the extre- mity of their abdomen, when they are irritated. 676. It would appear to be by simple absorption, that the chyle traverses the walls of the digestive tube and mixes with the Blood. This liquid is watery and colourless; it is not everywhere inclosed in vessels, but spreads itself out into the interstices, which exist between distinct organs, or which pre- sent themselves in the substance of their tissue. Insects are- destitute of a regular circulation. We can clearly see very rapid currents in certain parts of the body ; but the nourishing liquid does not perform a circle in such a way as to return constantly - to the point of its departure. There really exist amongst these animals only vestiges of a circulating apparatus. Fro. 425.— CIRCULATION w INSECTS. We see near the dorsal surface of the body a longitudinal tube (a, Fig. 425), which performs alternate movements of contrac- tion and dilatation, analogous to those of the heart among the higher animals. The nourishing liquid penetrates into it by lateral openings, furnished with valves to prevent its reflux ; and VOL. ii. i 102 CIRCULATION AND RESPIRATION OP INSECTS. being propelled forwards by the successive contractions of its different chambers, it passes out in front by a series of canals, of which some convey it to the head, whilst, others pass si4e- vvays and backwards (J), for the supply of the body with its appendages, the legs and wings. On returning from these parts, it re-enters the dorsal vessel, partly at its posterior extremity, and partly by the lateral orifices already mentioned. 677. It will be observed that, in this course, there is no special conveyance of the nutritious fluid, when rendered venous Head. 1st Pair of Legs — 1st Segment of Thorax Origin of Wing 2nd Pair of Legs —/t 3rd Pair of Legs Tracheae — Stigmata Fro. 426.— RESPIRATORY APPARATUS OF INSECT ' in its character by circulating through the tissues, to a particular RESPIRATION OF INSECTS. 103 organ for its aeration. If the Respiration of Insects were effected in the usual manner, by means of lungs, or at the external sur- face of the body, it would have been consequently extremely incomplete ; but the disadvantage which would appear to be the necessary result of this great imperfection in a function so import- ant as the Circulation, does not really exist. Nature lias made up the deficiency in the transmission of the blood, by conducting the air itself into all the parts of the body, by the aid of a multi- tude of canals, which communicate with the exterior, and which ramify minutely in the substance of the organs. These air- conveying tubes, known, as we have already said, under the name of trachea, present a very complicated structure : we can usually distinguish in them three coverings, of which the middle one is composed of a carti- laginous filament, roiled in a spiral, like an elastic spring. Sometimes they are simple ; but at other times they have a certain number of large dilatations, in the form of soft vesicles, which act as reservoirs of air. The openings by which the air penetrates into the tracheae are TUBE OF INSBCT* called stigmata or spiracles ; they are generally simple slits, like button-holes ; but sometimes they have two valves, which open and shut like the leaves of a folding-door ; and they are frequently furnished with a kind of sieve or grating, to prevent particles of dust, &c., being drawn inwards by the air. We usually see one pair upon the lateral and upper part of each segment ; but they are often concealed on the two last segments of the thorax. The means by which the air is renewed in the interior of this respiratory apparatus, appears to consist generally only of the movements of contrac- tion and dilatation of the abdomen. As we have already said, Respiration is very active amongst these animals : they consume a considerable quantity of air in comparison with their size, and they quickly die when they are deprived of oxygen ; but when they are in this state of apparent death, they may remain in it a very long time, without losing the power of being restored to life. G78. The greater number of Insects produce but very little 1C4 HEAT AND LUMiw^S IX OP heat ; but some of these animals, in certain circumstances, give out a quantity sufficiently considerable to raise their temperature perceptibly. This is the case with Bees, when they are disturbed in their hives ; and it is noticed that their Respira- tion then becomes very active. (See ANIMAL PHYSIOLOGY, §§410,411.) 679. Another most remarkable phenomenon, of which the cause is not fully known, is the production of light ; which is observed amongst some Insects. Of this the Lampyris, or Glow-worm, is an example, which is well known to almost every one who frequents our fields. The male has wings and is not luminous ; but the female, which is destitute of them, and which is often found on banks and hedges during the summer evenings, sheds a phosphorescent light that is often very brilliant. In another species of Lampyris which inhabits Italy, the indi- viduals of both sexes are at the same time winged and luminous ; but this singular property is especially remarkable among cer- tain Fire-flies, which live in the warm regions of America, and Fro. 428.— MALE AND FEMALE GLOW- , • i j i n • • ,i which produce, when flying in the WORM. darkness, a natural illumination of the most brilliant effect ; they are often placed by women in their hair as ornaments ; and we are told that the Indians use them to light themselves, when they travel by night. Among our Glow-worms, the light proceeds from certain spots situated upon the upper part of the two or three last rings of the abdo- men ; whilst among the Fire-flies, it comes from analogous spots placed upon the prothorax or corslet. It appears that the insect can vary at pleasure the intensity of this phosphoric light ; and that it continues during a certain time, when the animal is placed in a gas unfit for respiration, or even in a vacuum ; but that it is extinguished in cold water. 680. The sexes are distinct amongst these animals, and th< often exist very great differences between the male and ferns METAMORPHOSES OF INSECTS. 105 the common Glow-worm has already afforded us an example of this (Fig. 428). Nearly all Insects lay eggs ; some of them are, however, viviparous. At the extremity of the abdomen of the female, there is often a dart, a saw, or some other organ, fitted to make holes for the reception of the eggs (§ 667) ; and by an admirable instinct, the mother always lays them in a place, where her young will find near them the food which they will require ; and yet, in the greater number of cases, this food is not the same as she would seek for herself. During the early period of their lives, insects change their skin several times, and nearly always display some very singular phenomena, of which we have already seen an example amongst the Batrachian Reptiles. The greater number of them, at the time of their coming forth from the egg, neither resemble their parents, nor have the form which they will themselves acquire at a later period ; and before arriv- ing at a perfect state, they undergo changes so considerable, that we cannot better designate them than under the name of metamorphoses. 681. Insects, in general, pass through three very distinct states, known under the names of the larva state, the pupa or chrysalis state, and the imago or perfect state ; but the changes which take place are not always equally great ; sometimes these ch nges render the animal perfectly different, at other times they only consist in the development of wings ; and these vari- ous degrees of transformation are known under the names of complete, and of incomplete, metamorphosis. 682. The insects which undergo a complete metamorphosis, are always more or less vermiform (or worm -like), when they come from the egg, and when they are in a larva state ; their body is long, almost entirely soft, and divided into moveable rings, of which the regular number is thirteen. Sometimes they are completely destitute of feet ; at other times they are pro- vided with a variable number of these organs ; but the conform- ation of these is not at all analogous to that of the same parts in the adult animal. They have, nearly always, simple eyes, but they are sometimes entirely destitute of them ; their mouth 106 METAMORPHOSES OF INSECTS. is usually furnished with mandibles and jaws, whatever may be the form that it will afterwards assume ; and we often see the iirst of those orgins serving for locomotion, as well as for seizing FIG. 429.— LAEVA, FCPA, AND IMAGO OF fAPirio MACHACN. the food. These Larvae also differ in their form, and are some- times known under the name of Caterpillars, sometimes under that of Worms. — After having remained in this state for a longer or shorter time, and experienced several changes of skin, the wings begin to be formed beneath the skin, and the animal passes into the state of a pupa or chrysalis. During the whole length of this second period of their existence, these singular animals cease to take any food, and remain motionless. Some- times the skin of the larva, which in this case is never changed, dries up, and forms a kind of oval case, in the interior of which they remain shut up ; sometimes they are only covered by a METAMORPHOSES OF INSECTS.— SILKWORM. 107 thin pellicle, which lies over the external organs, follows all their inequalities of surface, and causes the insects to appear as if closely wrapped in bandages. 683. Before undergoing this change, the Larva often pre- pares a defence for itself ; and shuts itself up in a case, which it makes with silk, secreted by peculiar glands, and drawn out by means of a spinneret, a small tube attached to the lower lip. In other instances, it suspends itself by means of threads, or conceals itself in some hollow. It is, however, whilst the insect is in this state of apparent repose, that active operations are going on with- in the body, of which the result is the complete development of the entire organisation. Its interior parts become soft, and by degrees assume the shape that they will preserve ; the different organs, with which the adult animal ought to be provided, are developed under the envelope which conceals them ; and when this evolution is finished, it frees itself from this species of mask, spreads its wings, which are not long in acquiring firmness, and becomes a perfect insect or Imago. 684. As an example of this complete metamorphosis, we can- not make a better selection, than by taking the Bombyx Mori ; for this insect in its larva state pos- sesses for us an immense interest ; it is the silkworm, the rearing of which contributes so powerfully to the agricultural prosperity of the southern countries of Europe, and the FIG. ^.-SILKWORM, product of which gives origin to so much industry and wealth. This insect came originally from the northern provinces of China, and was not introduced into Europe until the sixth century. The Greek Missionaries brought some of its eggs to Constantinople in the 108 GROWTH OF THE SILKWORM. reign of Justinian, and, at the period of the first crusades, its cultivation was spread into Sicily and Italy ; but it was not until the time of Henry IV. that this branch of agricultural industry acquired any importance in the southern provinces of France, of which it now forms one of the chief sources of wealth. 685. The eggs of the Silkworm, when dry, have a gray-ash colour ; and with some care they may be preserved thus during a very long time without injury. In order that the work of incuba- tion may commence, and that the Iarya3 may be hatched, the eggs must be exposed for some time to a temperature of at least 60° Fahr. After having experienced an increasing heat for eight or ten days, they will become whiter ; and soon afterwards the larvag will begin to come, forth. These little animals, at the time of their birth, are only about a line and a quarter in length. Their body is long, cylindrical, annulated, smooth and commonly of a grayish colour ; at its anterior extremity we distinguish a head, formed by two hard and scaly tubercles, upon which are seen some black points, which are the eyes ; the mouth occupies the anterior part of this head, and is armed with strong jaws ; the three succeeding rings have each a pair of small scaly feet, and represent the thorax ; the abdomen is very much developed, and has no members upon its two first segments, but is furnished at the posterior end with five pair of fleshy tubercles, which resemble stumps, and which serve as so many feet. 686. In the south of France, these worms are called magnans; and the name of Magnanerie is given to the establishments in which they are reared. The first care that they require after their birth, is to separate them from their shells, and to place them upon frames, on which they find the food adapted for their support. For this purpose it is usual to cover the eggs with a sheet of paper, perforated with holes, through which the worms creep to get at the mulberry leaves placed above ; and when they are collected upon the boughs which are covered with these leaves, they are carried away upon the frames prepared for their habitation. The food of the Silkworm consists of Mulberry leaves ; and consequently it is on the cultivation of this tree, that the capability of rearing these insects depends. The White GROWTH OF THE SILKWORM. 109 Mulberry is the species the most generally employed for tnis purpose. It is a tree which grows to the height of fourteen or fifteen feet; it flourishes very well in all soils, and it is culti- vated with success even in the north of Europe ; but it never grows wild anywhere. The Mulberry came originally from China. Two Greek monks introduced it into Europe towards the middle of the sixth century, at the same time with the Silk- worm. Its cultivation was soon spread in the Peloponnesus, and gave to this part of Greece its modern name of Morea. Thence the Mulberries and the Silkworms were conveyed into Sicily under the direction of King Roger, and acquired a rapid extension in Calabria. Some French gentlemen who had accom- panied Charles VIII. into Italy during the war of 1494, having known all the advantages which that country derived from this branch of agriculture, wished to bestow the same upon their own country ; and brought some Mulberry trees from Naples, which they planted in Provence and Dauphine. About forty years since, the first of these trees planted in France was still to be seen at Allan, near Montelimart. At present the Mulberry trees cover a large part of the south of France ; they are even cultivated in the north ; and the success of some recent attempts appears to show, that they might be profitably cultivated in England. 687. Silkworms remain in the larva state for about thirty- four days ; and during this time they change their skins four times. The time comprised between these successive changes, constitutes that which the cultivators call the different ages of these little animals. At the approach of each change they become dull and cease eating; but after having cast off the skin, their hunger is increased. The quantity of food which they consume rapidly increases. It is computed that for the larv» proceeding from an ounce of eggs, there must be generally about seven pounds of leaves during the first age, which lasts five days; twenty-one pounds during the second period, which only conti- nues four days ; seventy pounds during the third period, which continues seven days ; two hundred and ten pounds during the fourth age, whose length is the same as that of the third age ; 110 GROWTH OP THE SILKWORM. and twelve or thirteen hundred pounds during the fifth period. It is on the sixth day of the last age, that the greatest voracity shows itself. The worms then devour two or three hundred pounds of leaves, and when eating make a noise which resem- bles that of a heavy shower. On the tenth day they cease eating, and prepare themselves to undergo their first metamor- phosis. We then see them endeavouring to climb upon the branches of small bundles of twigs, which have been carefully placed above the frames on which they have until then remained. Their body becomes soft, and a thread of silk comes out of their mouth, which they draw after them. They very soon fix them- selves, and throw around them a multitude of threads of extreme fineness ; and, suspended in the middle of this net- work, spin their Cocoon, which they form by continually turning themselves round in different directions — thus twisting round their body the thread which comes out from the spinneret, with which the lip is perforated. The silk, thus formed, is produced in glands, which have much analogy with the salivary glands of other animals ; and the matter of which it is composed is soft and glutinous at the time of its first appearance, but soon becomes hardened by the air. The result of the different twistings of this single thread, is to cause the different threads to adhere together, and to form an envelope, whose tissue is firm and shape oval. The colour of the silk varies; sometimes it is yellow, sometimes of a brilliant white, according to the variety of the worm which has produced it ; and the length of each thread often exceeds 1100 feet, but varies much, as does also the weight of the cocoons. The worms proceeding from an ounce of eggs may produce as much as 130 Ibs. of silk ; but such an amount is rare ; and from 70 to 80 Ibs. is the usual product. 688. In general, three days and a half or four days are suffi- cient for the larva to finish its Cocoon ; and if we then open this envelope, we see that the animal no longer presents the same appearance as before its seclusion. It has become of a brownish colour, its skin resembles old leather, and its shape is oval, a little pointed at its posterior extremity. AV'o no longer distin- guish a head or jaws ; but the poqteri ,c « -»\ •• mity is formed by METAMORPHOSES OP INSECTS. 1 1 1 two moveable rings, whilst in front we see an oblique band, representing the future wings of the perfect animal. The time during which the Bombyx remains thus shut up in a Chrysalis rio. 4ai.— CHRYSALIS or THE SILKWORM. FIG. 432.— SILKWORM MOTH. state, varies according to the temperature. If the heat is from 60 to 65 degrees, they come out of it in a perfect state on the eighteenth or twentieth day. In order to open the Cocoon, they moisten it at one extremity with a particular liquid, which they throw up from the stomach ; and then they violently strike their head against the part thas softened. When the Bombyx has thus finished its metamorphosis, it presents itself under the form of a Moth, with whitish wings ; its mouth is no longer furnished with jaws, as in its early state, but is prolonged into a rounded spiral trunk ; its legs are slender and lengthened, and its internal conformation differs as much from that of the Larva, as its external form. Almost immediately after this second birth, the Moths seek each other for the purpose of reproduction ; and the females subsequently deposit their eggs, of which the number sometimes amounts to more than five hundred for each of these insects ; and at last, after having lived in a perfect state for ten or twenty days, during which time they take no food, they die. 689. Among Bees we meet with still greater changes ; since in their Larva state they are completely destitute of legs, and resemble small worms. It is the same with Flies, Gnats, and a great number of other insects ; thus the vermiform animals which swarm in putrid carrion, and which are known under the name of Maggots, are nothing else than the larvae of the Meat-fly. The Gnats or Musquitoes, which fly in such large swarms, and 112 METAMORPHOSES OF INSECTS. FIG. 433. — G WAT AND LARVA. which render themselves so unpleasant to Man by their venomous punctures, live in the water during their larva state. They are then vermiform, destitute of limbs, and have the abdomen terminated by bris- tles and some appen- dages arranged in a radiated form (Fig. 333) ; and from their last ring arises a long tribe, by the aid of \vhich the animal draws in from the atmosphere the air which it requires. To breathe by this means, it suspends itself as it were from the surface of the water, with itt head downwards ; and we see it performing this movement at short intervals. The Chrysalis continues to live in the water, and to move about there ; but instead of breathing like the larvae, it draws in the air which it requires by means of two pipes, placed upon the thorax. It floats on the surface of the liquid ; and after having completed its metamorphosis, the per- fect insect uses the skin of the chrysalis as a boat, until its long legs and wings have gained sufficient strength to enable it to move on the surface of the water, or to fly away ; but if its body happens to be submerged, as often occurs when the wind upsets these frail barks, it is infallibly drowned. 690. The Insects with an incomplete metamorphosis also pass through the larva and chrysalis state, before arriving at the perfect state ; but here the larva only differs from the perfect insect by the absence of wings ; and the state of the chrysalis is only characterised by the gradual development of the wings, which, at first folded back and concealed under the skin, then become free ; but only acquire their full development at the period of the last change. We may mention, as examples of METAMORPHOSES OP INSECTS. 113 insects showing this kind 'of metamorphosis, the Grasshopper and the Ephemerae or Day-flies. These last display a remark- able peculiarity; since in general, insects change the skin for the last time, when they pass from the Chrysalis to the perfect state ; whilst the Ephemera experiences one more change, before arriving at its complete form, in which it only lives for the space of a few- hours. The larva of the Ephemera lives in the water, and differs very little from the adult, except in the shortness of its limbs, the absence of wings, and by the row of leaf-like ap- pendages which it bears on each side of its abdomen, and which it uses as organs of respiration and of motion in the water. The chrysalis only differs from the larva, by the presence of cases inclosing the wings. At the time when these organs should be developed, the in- sect comes out of the water ; and after having flut- tered about during some minutes, it takes its place upon an elevated object, and there performs some violent move- ments, by means of which it casts a way its enveloping membrane ; it is then only that its limbs attain their full length, and that the body acquires the colours which it will preserve. 691. Some Insects, although passing through the complete se- ries of transformations of which we have first spoken, appear, to a certain extent, to stop short in their development, never possessing any wings. The Fleas are thus circumstanced. When they come forth from the egg, they are destitute of feet, and have the form of small worms of a whitish colour. These larvae are very active, and roll themselves in a circle or a spiral. They soon become of a reddish hue ; and after having lived in this condition during 1'I'J. 434.— EPHEMERA VCLGATA ; LARVA, FUI'A, AN1) IMAGO. 114 METAMORPHOSES, INSTINCTS, AND CLASSIFICATION. twelve days, they shut themselves up in a small silky shell, of extreme delicacy, and are there transformed into a chrysalis ; at the end of about twelve days of seclusion, if the weather is warm, they come out of their envelope in a perfect state. 692. Again, there are some Insects which do not pass through any metamorphosis, and which are born with all the organs with which they will ever be provided ; but it is only among Apterous, or wingless, Insects, that this mode of deve- lopment exists. The Podura, which has been already referred to, and the Louse, are of this kind. 693. The class of Insects, which (as we have seen) is so remarkable for its organisation, is still more so in regard to the habits of the animals composing it, and the admirable instincts with which Nature has endowed a great number of them. The stratagems which they employ to procure themselves food, or to escape from their enemies, and the industry which they display in their labours, astonish all those who are witnesses of it ; and when we see them unite themselves into numerous societies, to make up for their individual weakness, helping each other by dividing the labour necessary for the prosperity of the commu- nity, providing for their future wants, and often even regulating their actions according to the accidental circumstances in which they find themselves placed, we are confounded at encountering amongst beings so small, and in appearance so imperfect, instincts so varied and so powerful, and intellectual combinations which so much resemble those of the reasoning powers. This subject will be more fully treated of in the latter part of the present volume. At present we must confine ourselves to a sketch of the classification of this group ; which, on account of the immense number of forms included in it, must be more slight than that which has been given of the preceding classes. 694. The subdivision of the Class into Orders is founded chiefly upon the structure of the Mouth, the conformation of the "Wings, and the nature of the Metamorphosis. Neither of these characters must be trusted to singly ; since within the limits of one group, we find considerable variation. Thus in almost every order, we meet with apterous or wingless insects ; an example of CLASSIFICATION OF INSECTS. 115 which we have already seen in the Glow-worm. Sometimes, as in that instance, the deficiency of wings is confined to one of the sexes — usually the female ; whilst in other cases, hoth sexes are destitute of these organs. Nevertheless there is a group, con- sisting of three small orders, in which the want of wings is the rule and not the exception ; and the insects brought together in these, are associated together on account of their resemblance to each other in general structure ; — -whilst, on the other hand, the wingless insects first alluded to are left among the orders in which they are placed, on account of their correspondence with other insects of those orders in the structure of the mouth, the nature of the metamorphosis, &c. 695. "We may divide the Class into two Sub-classes ; the members of the first of which (A) always undergo some degree of metamorphosis, and are usually possessed of wings in the perfect state ; whilst those of the second (B) undergo no meta- morphosis, and never become possessed of wings. — From the first sub-class may be separated one order, in which there are no wings ; and there then remain eight principal orders, which are classed according to the structure of the mouth and wings. SUB-CLASS A. Division a. — Winged insects undergoing metamorphosis. Order I. COLEOPTERA (Beetles). In these the mouth is formed for mastication ; the anterior wings are converted into hard elytra, or wing-cases ; the posterior wings are folded trans- versely (or cross- wise) during repose; and the metamorphosis is complete. Order IT. ORTHOPTERA (Grasshopper, Locust, fyc.). In these also the mouth is formed for mastication ; the anterior pair of wings is composed of a substance more resembling parchment; the posterior pair, when in repose, is folded longitudinally (or lengthwise) in the manner of a fan (Fig. 470) ; and the meta- morphosis is incomplete. Order III. PHYSOPODA ( Thrips). A small group closely al- lied to the Orthoptera and Neuroptera, but distinguished by the possession of delicate fringes round the elongated narrow wings. 116 CLASSIFICATION OF INSECTS. Order IV. NEUROPTERA (Dragon-fly, May-fly). In these, too, the mouth is formed for mastication ; but the anterior pair of wings, like the posterior, is membranous ; and the nerves of the wings form a close reticulation or network by their inter- lacement. The degree of metamorphosis is variable. ORDER V. HYMENOPTERA (Bee, Wasp, Saw-fly]. In these, the mouth is still furnished, as in the preceding, with prehensile mandibles, but the other parts are so formed as to be rather fitted for suction than for mastication ; the wings are all mem- branous, but the nerves do not form such a minute reticulation as in the preceding order ; the metamorphosis is always complete. The four preceding orders, in which mandibles are always distinctly present, form the group of MANDIBULATA ; the four succeeding, in which the mandibles are wanting or are completely changed in form, and in which the other parts are adapted for suction, being converted into a more or less complete haustellium or sucking-tube, are termed HAUSTELLATA. Order VI. LEPIDOPTERA (Butterflies and Moths}. These have the mouth furnished with a long trunk, coiled in a spiral when not in use ; the wings are all membranous, and are covered with minute scales, having the appearance of fine dust, but arranged with the most perfect regularity ; the metamorphosis is complete. Order VII. RHYNCHOTA (Bugs, Cicada, Lantern-fly, fyc.). In which the mouth consists of a jointed rostrum enclosing four bristles ; the wings are usually four in number ; and the meta- morphosis is incomplete. Order VIII. DIPTERA (Gnats, flies, #e.). In these there are but two wings ; the mouth is furnished with a sucking-tube ; and the metamorphosis is complete. Division b. Insects undergoing metamorphosis, but destitute of wings. This division includes but a single order. Order IX. APHANIPTERA (Flea, fyc.\ In this group, also, the mouth is formed for suction ; and the insects composing it are parasitic, living upon the juices of other animals. CLASSIFICATION OF INSECTS. 117 SUB-CLASS B. The small remaining section, consisting of Insects which un- dergo no metamorphosis, and are destitute of wings, includes three orders. Order X. ANOPLOURA (Louse). These are distinguished from the succeeding, by the absence of appendages to the abdomen, and by the suctorial nature of the mouth. Order XL MALLOPHAGA (Bird-lice). In these the abdomen is also destitute of appendages, but the mouth is formed for biting. Order XII. THYSANOURA (Spring-tails, fyc.). In these the abdomen is furnished with appendages, adapted for leaping. Besides these principal groups, there are some small interme- diate orders, by which the former are connected. These are not admitted, however, by all Entomologists. Thus the JEarwig tribe, which combines, in some degree, the characters of the Coleoptera and Orthoptera, is raised by many to the rank of a distinct order — DERMAPTERA, which leads from the first to the second order. Again, a separate order — TRICHOPTERA, has been formed to include the Caddice-fties, which are intermediate between the Lepidoptera and Neuroptera. And, lastly, there is a small group — STREPSIPTEKA, or RHIPIPTERA — which appears to be very closely allied to the Beetles, if indeed the Insects be- longing to it, which are all parasitic upon different species of Bees and Wasps, are not really members of the order Coleoptera. SUB-CLASS A. METABOLA ; or Insects undergoing a Metamorphosis. ORDER I.— COLEOPTERA, OR BEETLES. 696. The insects composing this Order, all of which are known under the common name of Beetles, are amongst the most numer- ous and best known of the whole class. The singular forms and brilliant colours exhibited by mftny of the species, the size of their bodies, the solid texture of their integuments, which facilitates their preservation, and the nature of their habits, which makes their capture more easy, have combined to render them an ob- VOL. n. K 18 GENERAL CHARACTERS OF BEETLES. ject of peculiar attention to Entomologists, many of whom have devoted themselves to this order exclusively. It is probable that from 30,000 to 40,000 species of Beetles alone now exist in the cabinets of collectors ; and we may safely affirm, that at least as many more yet remain to be discovered. 697. The conversion of the first pair of wings into elytra, or hard wing-cases, and the complete inclosure of the second pair by these, when the insect is at rest, constitute, as we have seen, the distinguishing features of the Order. The elytra, when expanded, are of little or no use in flight, generally remaining nearly motionless ; when closed, they meet along the back in a straight line, which is called the suture. The structure of the mouth, in this order, has been already described. The head is provided with two antennae, which vary in form, but which have usually eleven joints ; the form of these often differs considerably in the two sexes. The eyes are large and protuberant, espe- cially in the carnivorous species, and in those, the slowness of whose habits makes them need quick powers of sight, for the purpose of avoiding their enemies. Of the three segments of the thorax, the anterior one (commonly termed the corslet) is the only one that is visible from above ; the two others being covered by the wings and elytra, with the exception of a small triangular piece of the second segment (the scutellum), -which makes its ap- pearance in many species between the bases of the elytra. The two latter segments are firmly united to each other, and to the commencement of the abdomen ; and the chief movement of the parts of the trunk upon one another, is between the first and second segments of the thorax ; the latter being prolonged for- wards into a sort of footstalk, which is received into a cavity in the former, and thus serves as a kind of pivot for its movements. The abdomen usually consists of only six or seven segments ; the remainder of the nine, which properly form this part, being consolidated in the last. 698. Although the characters already mentioned are applica- ble to by far the greater number of insects included in th's Order, nearly all of them are subject to exceptions. Thus, there are many species, in which the organs of flight seem altogether GENERAL CHARACTERS OF BEETLES. 119 wanting, in one sex, at least, as in the female Glow-worm. In other cases, the elytra are fully developed, so as to cover the upper surface of the body ; but adhere together along the suture, so as to prevent the expansion of the wings, which are, consequently, never developed ; this is the case in the Blaps (Fig. 449). In other instances, again, the elytra, instead of simply meeting along the suture, fold over each other ; in others, they do not meet at all ; and there are some species in which the wings are folded, not transversely, but longitudinally, as in the next order. It is well for the Student to be aware that such exceptions exist in this, as in every other large natural group ; however definite its characters may generally be. In none of these instances is there an exception as to more than one or two of the characters in question ; the remainder conform to the usual type. 699. The Metamorphosis in this Order is invariably complete; and it is thus distinguished from all that approach it in the structure of its mouth, or in the character of the wings. The larvce are worm-like in their aspect ; the head is usually horny, the rest of the body soft. There is generally a pair of short jointed legs attached to each of the first three seg- ments, bearing some resemblance to those of the perfect insect. Those which pos- sess legs are usually active in their habits ; but there are others which, leading a retired life, and being born in the midst of their food (such as the Nut Weevil), no. 435.— LARVA, PUPA, AND PERFECT STATES OF CETONIA AURATA, OR ROSE-BEETLE. 120 SUBDIVISION OF BEETLE TRIBE. are destitute of members. The larvae of the carnivorous species have in general the most robust legs ; and in some of the herbivorous species these are assisted by fleshy tubercles, or pro-legs. A pair of these frequently exists on the last segment of the abdomen. Previously to undergoing its change, the larva often forms a case for itself, of bits of earth, or chips of wood, united by silken threads, or by gluey matter. The pupa, or chrysalis, is inactive, sometimes even for years, and takes no nourishment ; but the form of the future Beetle is plainly perceived, the different parts being encased in distinct sheaths. (Fig. 435). 700. There is much difficulty in forming a simple natural classification of this immense tribe, on account of the great num- ber of distinct species which it includes, and their strong general resemblance to each other. Hence it is often necessary to resort to characters of great minuteness as the ground-work of the system ; and it sometimes happens that, by the adoption of such a plan, tribes which are in reality closely allied in general struc- ' ture, are placed in different groups, whilst others are brought together which are in many respects dissimilar. The system here followed is founded upon that proposed by Latreille ; who took as the basis of his classification the number of joints in the tarsus or last portion of the foot (§ 664). The four following sections are thus formed. I. PENTAMERA (five-parted), in which the tarsi of all the feet are distinctly 5 -jointed. II. HETEROMERA (differently-parted), in which the tarsi of the first two pairs of feet are 5 -jointed, and the two posterior 4-jointed. III. TETRAMERA (four-parted), in which all the tarsi appear to be 4-jointed. (The fifth joint exists in these, although it is very minute, and concealed in one of the others.) IV. TRIMERA (three-parted), in which all the tarsi have three distinct joints. (A fourth of small size is also present.) Each of these sections contains several families ; of which the most important will now be noticed. It must be borne in mind, that the characters drawn from the number of joints in the tarsi, CARNIVOROUS BEETLES. 121 apply only to the majority of the species of the groups, so that most of them include some species which do not strictly fulfil the conditions implied in their names. 701. Section I. PENTAMERA. The first family of this sec- tion consists of Beetles which are exclusively carnivorous ; hunting after, and devouring, other insects ; and being carnivorous even in their larva state. These CARNIVORA are characterised by the possession of six palpi, — there being two to each of the maxillae (Fig. 415), — and by the termination of these jaws in a sort of claw or hook. Some of them are terrestrial, and others aquatic; in the former the legs are adapted only for running; in the latter, they are modified for swimming. The terrestrial divi- sion of the group, the tribe of the GEODEPHAGA, is composed of two very large families, the Cicindelidce and the Carabidce, charac- terised chiefly by the form and mode of attachment of the hook at the end of the jaws. The Cicindelidce. have the body usually of a dark or light-green colour, varied with shining metallic tints, and with white spots upon the elytra ; they frequent dry situations exposed to the sun, run very quickly, fly off when they are ap- proached, and alight again at a short distance. The larvaa burrow in the earth, forming a cylindrical hole of considerable depth ; in the process of excavation they use their jaws and feet, and load the concave back of their heads with the grains of earth which they have detached ; thus loaded, they as- cend, resting at intervals, and fixing themselves to the inner walls of their burrow by the assistance of two hooked tubercles on the back ; when Pv||r \ arrived at the orifice, they jerk off * their load to a distance. Whilst lying in ambush, the flat plate of the head exactly stops the mouth of the hole, forming a flat surface with the surrounding soil. When their prey comes within their reach, they rush upon it with great ferocity, and seize it between their powerful jaws ; and their voracity is even extended to larvae of FIG. 436. — CICINDF.LA CAMPESTRIS, AND LARVA. 122 CARNIVOROUS BEETLES; — CARABUXffi. the same kind. They close the orifice of their burrow when they change their skin, or undergo their metamorphosis into the pupa state. There are several British species of this group ; as well as a large number of brilliantly-coloured tropical species, of which many are apterous. 702. The family of Carabidce is of very great extent ; above 2000 species having been brought together by a single collector. Their bodies are of very firm consistence, whereby they are enabled to creep under stones and through fissures, and are also prevented from being injured by the insects they attack. They prowl about on the surface of the ground, under stones, &c., beneath the bark of trees, or the moss growing at their roots, in search of their insect prey, which con- sists chiefly of the herbivorous species of their own order. Some of them are nocturnal in their habits, feeding upon Cockchafers and other species of herbivorous beetles that fly abroad during the night. The habits of this tribe are not exclusively carnivorous, however, for some species, generally found in corn-fields, are clearly ascertained to feed upon growing grain. — Many species of this tribe are provided with a very curious means of defence ; being enabled to exhale a very fetid odour, and to discharge from the abdomen, to a considerable distance, an acrid fluid, capable of producing much irritation. In the Brachinus this fluid is so highly volatile, that, immediately on coming in contact with the air, it passes into a bluish vapour of very pungent scent, and makes a sort of explosion ; hence the species possessed of this power have been termed Bombardier Beetles. The larger species are found only in tropi- BEETLE. caj regions ; but the small species represented in the accompanying figure, is a native of England. The Bombardier Beetles for the most part live in societies, especially in spring ; and are found concealed under stones. Of the entire family, a AQUATIC CARNIVOROUS BEETLES j— DYTICUS. 123 considerable proportion are found in Britain and other temper- ate countries; but the largest and most brightly-coloured species are confined to warmer climates. 703. The aquatic Carnivora, or HYDRADEPHAGA, form a tribe far less numerous than the terrestrial species -r and are at once distinguished by the peculiar modification of the legs, which adapts them for swimming,— these members being flat- tened, and fringed with bristles, so as to serve as oars. They live, during their larva and perfect states, in water ; but they quit that element to undergo their metamorphoses, and to pass the time of their pupa condition. The larvae have the body long and narrow, with a strong head armed with powerful mandibles ; and they are of very active carnivorous habits. Both the larva? and the perfect insects can only breathe air, and are obliged to come to the surface occasionally for that purpose. The Dyticus, the principal genus of this tribe, is com- mon in fresh and placid waters, such as lakes, pools, or ditches. Its larva feeds upon other aquatic larvas, such as those of dragon - FIG. 439.— DYTICUS MARGINALIS AND LARVA. n> flies, gnats, &c. ; and moves quickly through the water, by means of strokes with its expanded tail. The pupae may be found buried in the adjoining banks. The imago also is very voracious, feeding principally upon the juices of the animals it attacks, which are often much larger than itself; an individual has been kept in a large bottle of water for three years and a half, being fed once a week or oftener with a bit of raw beef. 704. The GYRONECIIINA, or Whirligigs, as they are com- monly called from their peculiar movements, are placed with the aquatic Carnivora by many authors. In these the second pair of maxillary palpi does not exist ; and the antennae, instead of being slender and filiform, are short and clubbed. The com- 124 GYRINI. — BRACHELYTixA. mon Gyrini (Fig. 399) may be met with, from the first fine days of spring until the end of autumn, on the surface of quiet waters, and even upon that of the sea, often assembled in great numbers, and appearing like brilliant points. They swim with great agility, often curveting in a circular direction, — whence their common name. Sometimes they remain stationary with- out the slightest motion ; but no sooner are they approached, than they escape by darting under the surface of the water, and swimming off with the greatest agility. The four hind-legs are used as oars, and the anterior pair for seizing the food, which appears to consist of the dead bodies of insects and other small aquatic animals. When they dart beneath the surface, a bubble of air, like a silvery ball, remains attached to the hind part of the body. The larva is long and slender, and each side of the body bears a series of fringed filaments, which are evidently respiratory organs. — The larva undergoes its change to the pupa state in the interior of a small cocoon, which it attaches to the stem of some aquatic plant above the surface of the water. 705. The next tribe of the Pentamerous Beetles is that of BRACHELYTRA, distinguished, as the name imports, by the short- ness of the elytra. They have only four palpi. These insects run and fly with equal agility ; they are ex- tremely voracious, not only feeding on living prey, but also deriving their nutriment from dead and decaying animal and vegetable matters. The majority live in the earth, amidst manure and putrescent substances ; others are found among Fungi and rotten wood, and under stones ; others, again, are only met with near water ; and a few of the smallest are only found in flowers. The - larvae feed on the same substances, and in the same situations, as the perfect insects ; and greatly resemble them in form. These Beetles, — of which one of the largest is frequently to be seen running about garden- walks, and is commonly known under the name of the Devil's Coach-horse, — turn up the end of the body when touched, bendjng it in all directions ; and they possess the power of emit- rniLIIYDRIDA.— NECROPHAGA. 125 ting a strong odour, which is in some instances extremely fetid, and which serves as a means of defence. 706. The PIIILHYDRIDA possess antennae with a club-like termination ; but these are usually shorter than one of the pairs of palpi. Nearly all of them are aquatic, and have their legs adapted for swimming, somewhat in the manner of those of the Dyticus. The most remarkable genus is the Hydrous, of which one .large species, an inch and a half long, oval, of a brown-black colour, and highly polished, is common in the ponds and ditches of this country. It swims and flies well, but walks badly. The eggs are laid in a sort of cocoon, spun by the female, and coated with a gummy matter that is im- pervious to the water on which it floats. The larva?, which have a worm-like body, with six feet, and with sharp mandibles arming the head, are very voracious ; feeding upon Tad- poles, the young fry in fish-ponds, and small fresh-water Mollusca. The Sphceridia arid Cer- cyons, which also belong to this group, are found in the excrements of the larger mammalia, upon which they and their Iarva3 feed. 707. The succeeding tribe, that of the NECROPHAGA, consists of those Pentamerous Beetles, whose antenna end in a club- shaped enlargement, whose maxillary palpi are always consider- ably shorter than the antennae, and whose limbs are not con- tractile. They are all terrestrial. They feed for the most part on animal matter, at least in the larva state ; but a large pro- portion of them prefer substances which are in a decaying or putrescent condition. One of the most interesting genera is the Necrophorus or Burying Beetle; so named from its habit of excavating the ground beneath the dead bo- dies of small quadrupeds, such as Mice or Moles ; when they have interred the carcass, they deposit their eggs in it, and the larvae, when hatched, feed upon the flesh. — Another genus, which includes a large number of species, is the Dermestes ; 126 HELOCEEA.— LAMELLICORNIA of which the larvae (whose bodies are hairy) are very voracious, feeding on the skins or carcases of animals, often destroying col- lections of insects, and committing great ravages in fur-ware- houses. 708. The HELOCERA, which form the next tribe, also have clubbed antennas, but their limbs are singularly flattened, and so arranged that each part can be folded closely up to the others, in order that the whole may occupy the smallest possible space ; in this contracted condition, the limbs are received in small cavities in the lower surface of the body. In their habits these insects vary a good deal. The Histers or Mimic Beetles, which are of a flattened, quadrangular form, with a very hard, smooth, and shining integument, usually of a black colour, are found some- times in the dung of the larger animals, and sometimes in putres- cent animal matters, whilst a few of them dwell beneath the bark of trees. The ByrrhidtB, commonly known as Pill- Beetles, from their spherical or convex ovate form, are usually found crawling on the ground in sandy localities, although a few of them, like the Dermestes in the preceding tribe, frequent houses and warehouses, where they are often exceedingly destructive to dried animal matters. 709. The next tribe of the Pentamerous section, the LAMELLICORNIA, is of very great extent, as well as one of the most striking of the whole Beetle tribe, in regard to the size of the body, and the variety in the form of the head and thorax in the different sexes ; and also, moreover, in those species which in their perfect state live upon fresh vegetable substances, in respect to the brilliancy of the metallic colours with which they are ornamented. But very many of the other species, which subsist on decomposing vegetable matter, are of a uniform brown or black colour ; although some are not inferior in brilliancy to the preceding. All have wings ; and they crawl but slowly along the ground. None of them are aquatic. Their food, especially in the larva state, consists of dung, manure, tan, and particularly, in some species, of the roots of vegetables ; whence these insects often occasion great loss to the cultivator. In the perfect state, many of them have the LAMELL1CORNIA ; — SCARAB JEI. 127 same tastes as their larvae ; whilst the larvae of some which feed upon the roots of plants or rotten wood confine themselves, when mature, to the sweet juices of flowers, which they lap up with their delicately fringed jaws. — This tribe receives its name from the peculiar conformation of the antennas, which terminate in a mass formed of from three to seven joints ; these are flattened into plates or lamellae, and are sometimes arranged like a fan or the leaves of a book, sometimes in the manner of a comb, and sometimes inclosing one another. The tribe is divided into two principal sections, the Scarabcei and the Lucani. 710. Of the Scarabcei, one subdivision, including the sacred Beetle of the Egyptians (Fig. 443), feed principally upon the excrements of various animals ; and they inclose their eggs in balls of the same (whence they have been called Pilularii), which they roll along with their hind feet, several often being in company, until they reach the hole in which these are to be deposited. The majority of the dung-eating species, however, do not take so much trouble in providing a shelter for their young, but content themselves with depositing their eggs in the freshly dropped excrements of the larger animals, where they and FIG. 443—ATEUCHT78 (SCARA- FlO. 444.— GEOTRUPES 8TERCORAMITS. BJEDS) ^QYPTIORTJM. their larvae may be found in great abundance. Of these we have a characteristic example among British species, in the Geotrupes stercorarius, the common Dor or Shard-borne Beetle : 123 LAMELLICORNIA ; — BCA&ABJEL FIG. 445.— DYNASTES HERCULES. which is one of the commonest of all Beetles in this country. One of the most remarkable amongst foreign species is the Dy- nastes Hercules, a native of Brazil, which attains the length of 5 inches, and of which the male possesses an enormous horn projecting from the head, which is opposed by a corresponding protuberance from the thorax. To this group also belongs the Melolontha vulgaris or common Cockchafer ; which is most destructive to vegetation in both its larva and perfect conditions, feeding on the roots in the one case, and on the leaves and young shoots in the other. The larvae live for three or four years beneath the ground ; becoming lethar- gic in winter, but actively voracious in sum- mer. Their excessive multiplication is usually prevented by birds ; but if these be kept away, they increase very rapidly, and become a complete pest to the cultivator. The perfect insects sometimes make their appearance in such swarms, as to devastate an entire forest. This group also in- cludes the Cetonia aurata or Rose-beetle, a very common British insect, of which a figure has been already given (Fig. 435) ; it is about an inch long, of a shining-green colour above, coppery- red beneath, with white marks on the elytra. In its larva state, it lives in the ground feeding upon roots, and is often met with in ants' nests ; but its object in seeking such a dwelling-place is still unknown. After remaining about three years in the larva state, it makes a sort of cocoon of fragments of vegetable matter, glued together by an excretion of its own ; in this it passes the winter in the state of an inactive pupa, from which it emerges in the following summer in its perfect form. The Rose-beetle FIG. 446— LARVA OF COCKCHAFER. LUCANI. — 8EEEICOKNIA 129 flies well, with a considerable humming noise, during the hot- test part of the day ; and goes from flower to flower (not con- fining itself to Roses, but seeming to prefer them), sucking the honey from their interior, and sometimes devouring their necta- ries. The larvae of most of the allied species live in rotten wood, and the perfect insects of some of them feed upon leaves. 711. The Lucani, or Stag-beetles, derive their common name from the peculiar form of the mandibles, which are very large, curved, and toothed, like stags' horns (Fig. 416). The Lucanus cervus, a highly-characteristic species of the group, is one of the largest of British insects, the males being two inches or more in length. This species flies about in the evening, in the middle of the summer especially round the oaks, upon the wood of which it feeds during the larva state, in which it remains for several years before undergoing its final trans- formation. The accompanying figure represents the .Dorcus parallelipipedus, or small Stag-beetle of this country ; which is far less striking than the larger species in regard to the deve- lopment of its mandibles. Some of the exotic species of this group are very large and splendidly co- loured. 712. The next tribe, SERRICORNIA, is distinguished by the toothed or serrated form of the antennae. Some of this group, having the body of solid consistence and oval in form, have the head buried, as it were, in the thorax, which advances on its two sides, nearly as far as the mouth ; whilst at the hinder part of the prosternum there is a small cavity, which receives the point of a spine, springing from the anterior margin of the second thoracic segment. In this manner is formed the Buprestis, dis- tinguished for the splendour of its colours ; many of its species having spots of golden hue upon an emerald ground ; whilst in others, azure glitters upon the gold. The largest and most bril- liant species are found chiefly in tropical climates, which these FIG. 447.— DORCUS PARALLELT- PIPEDU8. 130 SERRICORNIA ;— ELATER. insects appear especially formed to inhabit ; our native species, which are not above a quarter of an inch long, being observed to fly with the greatest activity in warm weather. They live among trees ; and, if an effort be made to seize them, they coun- terfeit death, and fall to the ground. — The Beetles belonging to the allied genus Elater, are commonly called Skip-jacks ; for, when laid on their backs, being unable to raise themselves on account of the shortness of their legs, they spring perpendicu- larly in the air, so as to alight upon their feet. They are enabled to effect this feat of activity by the peculiar mode in which the first and second segments of the thorax are attached to each other. The prothorax, which is long and thick, is flattened be- hind, so that it is enabled to bend backwards to a considerable extent. When laid on its back, the insect avails itself of this power, and throws up the middle of its body until it rests only upon the head and the posterior extremity of the elytra, when the spine of the second segment is drawn out of the pit already mentioned ; then by a sudden exertion of muscular power the body is straightened until the spine strikes forcibly into the cavity appropriated to its reception, and the sudden check thus caused is sufficient to throw the Beetle to a considerable height in the air. The larva of one of the British species, known to the farmer as the Wire-worm, does much injury by devouring the roots of the corn. A species of Elater, inhabiting the West Indies and South America, is one of the most brilliant of the Fire-flies ; having two brightly-illuminated spots upon the front of the thorax, and a portion of the abdomen which is uncovered during flight being also very luminous. — The common Telephori, well known to children under the names of Soldiers and Sailors, are examples of another section of this group, in which the in- teguments are usually soft, whilst the sternum is always desti- tute of the spine and pit above mentioned. Nearly allied to these is the Lampyris or Glow-worm, of which sufficient men- tion has been already made. — To the same very numerous family belong the genus Ptinus and its allies. These are insects of small size and slow movements ; many of them are destitute of wings ; and those which possess them seldom use them as means DEATH-WATCH. — MELASOMA. 131 of escape. Fro. 448 — A.XOBIUM srniATUM. NATURAL SIZE AND MAGNIFIKD. When touched, they counterfeit death by lowering the head, drawing in the antennae, and contracting their feet ; and they remain in this position for some time. Their colours are always obscure, and but slightly variegated ; and they live in dark places near or upon the surface of the ground. Of the genus Ano- bitim, nearly allied to Ptinus, many species inhabit the interior of our houses, where they do much injury in the larva state, by gnawing furniture, books, &c., which they pierce with little round holes, like those made by a drill. Other species feed upon flowers, wafers, preserved specimens of natural history, &c. The curious sound mac^e by them — from which have arisen the superstitious ideas that gave origin to their common name of D>ath- watch — lias been elsewhere noticed (ANIM. PHYSIOL. § 677). The species are remarkable for the pertinacity with which they feign death when alarmed ; preferring, it is said, to suffer death under a slow fire, rather than give the least sign of life. 7 1 3. Section II. HETEROMERA. The Coleoptera of the Se- cond section, characterised by possessing five joints in the tarsi of the two anterior pairs of feet, and only four i\f-**Jj in the posterior tarsi, *£_£ feed entirely on veget- / I IX ab*6 su^stances » tnev are V I k^ all terrestrial, and most / \\J x of them frequent dark places. — In thefirst tribe, the MELASOMA or black- bodied Beetles, the body is usually of an ashy- and the wings are for the most part ab- Fro. 450. TBNRBRIO Mo- Fro. 449.— KLAPS MORTISAGA. brown or black colour sent, the elytra being united along the suture. They usually live in the ground, beneath stones, or in the sand — often also in 132 BLAPS. — CANTHARIS. low and dark parts of buildings, such as cellars, stables, &c. The insects of this tribe are very tenacious of life ; individuals having been known to remain alive for six months without food, and pierced through with a pin. To this family belong the Blaps mortisaga, a beetle often found in dark and dirty places about houses ; and the Tenebrio molifor, of which the larva, known under the name of the meal-worm, lives in corn and flour, whilst the perfect insect also frequents bake-houses, corn-mills, &c., where it may be often found in the eaves. 714. The TRACHELIA (wecfod-beetles), are so named from having the head, which is triangular or heart-shaped, carried on a kind of neck, which separates it from the thorax. The body is soft ; and the elytra are flexible, and sometimes very soft. The majority of this group live in the perfect state upon different vegetables, devouring the leaves, or sucking the juices of the flowers. — Many of them, when seized, de- press the head and contract the feet, as if riG- VESICATOHIA. they were dead. Their colours are often very brilliant. This is well seen in the Cantharis vesicatoria, commonly known as the Blistering-fly, which is of a shining green metal- lic hue ; this insect is most abundant in Spain, but appears about midsummer in France, and is found in great numbers on the ash and lilac, of which it consumes the leaves. The most abundant British species of the group belong to the genus Meloe, some of which are well known under the name of May-worms, from their generally making their appearance on fine days in the month of May. They are soft, sluggish creatures, usually of a violet black colour, with short elytra, which wrap over each other at the base, and cover no wings. They are found princi- pally in meadows and on sandy heaths, where they crawl about upon the herbage or visit the flowers. Their larvaB, which are hatched from a mass of eggs laid by the female in a small hole in the ground, are minute active creatures, furnished with six well-formed legs ; they quickly find their way into flowers, ex- hibiting a great predilection for the common Buttercup. Here RHYNCHOPHORA, OR WEEVIL TRIBE. 133 they attach themselves to the bodies of the wild Bees, which visit these flowers in search of honey, and are by them conveyed to their nests, where they feed upon the larvae of the Bee. When full grown, the larva is a large, black, soft grub. The larvae of some other species are also parasitic in their habits, always selecting the progeny of Bees and Wasps for their attacks ; the majority, however, live in rotten wood or beneath the bark of trees. 715. Section III. TETRAMERA. All the Beetles of this group, likewise, — consisting of those which have four joints in all the tarsi, — are vegetable feeders. The perfect insects are found upon the flowers and leaves of plants ; the larvae are often produced in their interior ; and, when thus hatched in the midst of their food, their legs are commonly very imperfect. Very often the true legs are almost entirely absent, and their place supplied by fleshy tubercles. The first tribe, that of the KHYNCHOPHORA, or the Weevil tribe, is distinguished by the prolongation of the anterior part of the head into a kind of muz- zle (Fig. 452, D). The number of species in this family is very great. Many of them are extremely de- structive ; especially the Calandra grana- ria, which commits great havoc in gran- aries, both in its larva and perfect states. The accompanying figure exhibits the history of the develop- ment of the Balani- Fio. 452.-A, a brunch of the filbert tree; a, a healed „„, nUCUm Or Nut- wound caused by the introduction of the egg of the nut- weevil ; b, extremity of the nut ; c, exit hole of the Weevil, whose larva grub ; B, the grub of the nut-weevil ; c, tfie pupa of the . i r j banie ; D, the perfect insect (Balaninus nucum). 1S SO COmmonly lOUnd in nuts, filberts, &c. The egg is introduced by the parent when the nut is young and soft ; and the wound made by it heals over. The larva, when it VOL. II. L 134 XYLOPHAGA, OR WOOD-EATING BEETLES. comes forth from the egg, feeds upon the kernel in which it is imbedded ; and when full grown, it bores through the shell, and escapes, leaving a small round orifice. It then falls to the ground, in which it buries itself to a sufficient depth to afford it a protec- tion against the frosts of winter. In the spring it undergoes its change to the pupa state, and soon after emerges from its con- cealment in its mature form. — To this tribe belongs one of the most splendid of all Beetles, the Curculio imperialis, well known as the Diamond-beetle, which is a native of South America, and very abundant in some parts of that country. There are small species belonging to our own island, however, which are scarcely less brilliant when mag- nified under a good light. 716. Nearly allied to the Weevils, is a small group of Tetra- merous Coleoptera, which has received the name of XYLOPHAGA / 7 \ FIG. 453.— 1, 2, TOMICUS TYPOGRAPHIC; 3,4, 5, 6, HYLTJKGUS (Or WOOd-eaterS), On PINIPF.RDA (natural size and magnified). account of the peculiar habits of the Beetles composing it. They usually live in wood, which their larvse pierce in every di- rection ; and, when abundant in forests, especially those of pines and firs, they de- stroy large numbers of trees in a few years. They are destitute of the prolonged muzzle of the last order, and have short antennae, FIG. 4.54. Trac* of Typographer Beetle. thickened towards the tips (Fig. 453). One of the most destructive species is the XYLOPHAGA.— LONGICORNIA. 135 Tomicus typographies, or the Typographer beetle (so named from the figure of its burrows), which has at different times ravaged the forests of Germany. It devours, both in the larva and perfect states, the soft wood beneath the bark, which is most essential to the vegetative processes ; and thus causes the death of the tree. It was reckoned that a million and a half of pines were killed by this species alone in the Hartz Forest, in the year 1783 ; and that as many as eighty thousand individuals were ordinarily engaged in the destruction of each tree ; whence the whole number at work in the forest at once must have been one hundred and twenty thousand millions. 717. We now come to the LONGICORNIA, distinguished by the great development of the antennae, which are almost al- ways at least as long as the body, and often longer. The larvae mostly reside in the interior of trees, or under the bark ; and are destitute of feet, or have them very small. They are furnished with robust mandibles, and do much injury to trees, especially Fzo. 4G5.— CALLICHROMA MOSCHATA when they are of large size, by burrowing deeply into them. They are vegetable-feeders in their perfect state also, and do great injury to plants ; some attacking the leaves, and others the roots. Many of them produce a slight creaking sound, by the friction of the prothorax upon the base of the scutellum. — 136 PHYTOPHAGA ; — CASSIDID.E. Several of them are brilliantly coloured, especially the tropical species ; and some are remarkable for exhaling an agreeable musky odour. This is the case with a British species, the Cal- lichroma moschata, or Musk-beetle, which is about an inch long, entirely green, or shaded with a blue or golden hue, and very common upon willows. The genus Acanthocinus is remarkable for the spiny projections from its ely- tra ; and the species represented in the accompanying figure de- rives its specific name (which means mirror-bearing) from its having a bright burnished disc on each of the elytra. 718. The last tribe of the Te- _ , FIG. 456— ACANTHOCINUS SPECULIFER. tramerous section, that of the PHYTOPHAGA, presents many points of interest, on account of the singular forms, and remarkable habits, of many of the species which it includes. The insects composing it are usually of small size, but are often ornamented with metallic and brilliant colours ; they are generally slow in their motions, timid, and fall to the ground when an attempt is made to seize them, folding their antennae and legs beneath the body ; many species leap well. Like the Longicorns, they are destitute of the rostrum, or muz- zle-like prolongation of the head, which is characteristic of the Weevils ; but their bodies are usually of a circular or oval shape, rarely elongated ; their antennas are comparatively short, usually thread-shaped, or slightly thickened toward the tips ; and their mandibles are small, and quite concealed when closed. The Iarva3 have six feet, and a soft body ; they feed, like the perfect insects, upon the leaves of different vegetables, where they ordi- narily affix themselves by means of a glutinous secretion ; and they frequently undergo their change into the pupa state in the same situation, the cast-skins of the larva? being crumpled up at the extremity of the body of the pupse. The first family of this tribe consists of the Cassidida, or Tortoise Beetles ; these have a flattened body, surrounded by a margin, which is formed by a CASSIDIDJE; — CHRYSOMELnXE. 137 FIG. 457.— CA8SIDA V1RJDIS, IN ITS DIFFERKNT STATES ; a, larva ; 6, tlie same on a leaf, with its covering of excre- ment ; c, pupa ; d, perfect insect. prolongation from the thorax and elytra, and which even conceals the head ; and they are able to lie so close upon the surface of the leaves, that no part of the body or limbs is visible. Their colours are much varied, and often very prettily arranged in spots, points, rays, &c. The commonest species in this country is the Cassida viridis, which is about one third of an inch long, of a green colour, with black thighs. Its larva, which lives on thistles and arti- chokes, has a very flat body, with spines set on the edges; and it has the singular habit f of covering itself with its own excrement, which it attaches in a mass together, and carries on a sort of fork, arising from its tail. The pupa, also, is very flat, with thin, toothed appendages at the sides of the body ; and its thorax is broad, and prolonged forwards in a rounded expansion, which covers the head. 719. In the family Chrysomelidce, or Golden Beetles, this expansion of the thorax is generally wanting ; the body is usually of a hemispheric or ovate form, the base of the thorax being as broad as the front edge of the elytra ; and the surface is usually bespangled with the most brilliant hues, in which blue, green, and gold, are pre-eminently conspicu- ous. Their motions are generally slow, and many of them are destitute of wings. Of the genus Chry- somela, the C.populi is one of the commonest British species ; it is of a blue-black colour, and has red elytra, tipped with black ; it is found upon the willow and poplar, in the larva as well as in the perfect state. As in the FIG. 458.— CHRYSOMELA POPULI; a, larva; 6, pupa ; c, imago. 138 TIMARCHA.— GALERUC1D/E.— CRIOCERIDJ-. preceding group, the exuviae of the larvae are found collected into •a mass, at the extremity of the body of the pupa ; and, in some instances, the larva, before undergoing its transformation, attaches itself to the leaf by a glutinous exudation. Of the apterous group, the Timarcha is the principal genus ; and the T. Icevigad t is a common British species, varying in length from half to thn.-fl quarters of an inch, and frequenting woods, turf, and low herb- age. It crawls slowly, and emits a reddish-yellow fluid from the mouth and joints when disturbed ; from which circum stance it is commonly known by the name of the Bloody-now Beetle. The larvae bear a strong resemblance to the perfect insect, both in appearance, sluggishness of movement, and general habits ; when disturbed, they roll themselves up in the manner of a Wood-louse. — The family Galerucidas may also be men- tioned as containing the genus Haltica ; which is composed of a group of minute brightly-coloured Beetles, whose larvae devour the leaves of cultivated vegetables, and occasionally commit great devastations by their num- bers and voracity. One of them occasionally attacks the turnip in this country ; and from its great leaping powers, may well be de- signated the Turnip-flea. The Turnip-fly belongs to quite a FIG. 459-HALTicA NEMORUM.or TURNIP- different group. (§ 753.) BEETLE; natural size and magnified. L vo 720. The Criocerida depart somewhat from the general characters of the tribe, and approach the Longicorns, in having the body elongated, and the thorax narrower at the base than the elytra. The Donacice, a small group of pretty little Beetles belonging to this family, also differ from their near- est allies in their habits in the larva state; their larvae feeding in the interior of the stems of aquatic plants, upon which the perfect insects may be found F™'8 4^'^Jai.K" abundantly during the summer. The other species of the family feed upon leaves, in the same way as the other Phytophaga, exhibiting an especial preference for Liliaceous TRIMERA, — ST11EPSI PTERA. 139 Lady-cows. plants. One species, the Crioceris Asparagi, which is of a blue colour, with the thorax red, and the elytra yellowish-white with blue markings, feeds, in the larva state, on the young sprigs of Asparagus ; and is sometimes so abundant, as to do considerable injury to the gardener. It is also remarkable for covering itself with a sort of screen, composed of its excrements, in the same way as the larva of the Cassida, although it is destitute of the curious fork on which the latter carries its natural parasol. 721. Section IV.— TRIMERA. The Beetles of this section are, for the most part, of small size, and not very numerous. Their habits are various, a portion feeding on Fungi, arid the remainder chiefly upon Aphides. To the latter section belongs the genus Coccinella, of which several species are known in this country, under the name of Lady-birds or They sometimes appear in great profusion, and have created much alarm. It is erroneous to sup- pose, however, that they do any injury to vegeta- tion ; |br, on the con- trary, they are of great benefit to plants, by feeding on the Aphides which infest them ; and this they do both in the larva and perfect states. 722. This is probably the best place in which to introduce a small group of singular insects, forming the order STREPSIPTERA or RHIPIPTERA, of many entomologists ; the insects belonging to it being evidently closely related to the Coleoptera, of which they are now regarded by many as forming an integral portion. They are parasitic upon various species of Bees and FIG. 462.— A, Stylops Dalii, nat. size ; B, magnified ; C, Andrena, with the heads of two females ex- serted between the abdominal rings, a ; D, female extracted and magnified. 140 STREPSIPTERA. Wasps, usually exhibiting a preference for the solitary Bees of the family ANDRENIDJE. The name of the group, which means "twisted wings," has reference to certain curious appendages, which are seen in front of the wings ; these appendages are at- tached to the second segment of the thorax, whilst the wings (of which there is only one pair) proceed from the third ; hence the former are to be regarded as the altered rudiments of the ante- rior pair of wings. The organs of the mouth are reduced to a very rudimentary condition ; the eyes are large and prominent, being mounted on footstalks, as in many Crustacea. The anten- nae are of singular form, being usually furnished with an internal branch or projection, nearly as long as the antenna itself. The wings are large, and folded in a fan -like manner ; when in motion, they make a buzzing sound, which is considerable in proportion to the size of the animal. The third segment of the thorax, to which they are attached, is developed to an extraordi- nary size in proportion to the rest of the animal, and the abdomen is very small. — These are the characters presented by the male, the only sex which was correctly known until very recently ; and it was not until the discovery of the mode of life of these curious creatures, and thus of the true female, that their proper place in the system of Entomology could be determined. 723. The phenomena of their existence are very singular. Their larvae are parasitic upon those of different species of Bees and Wasps ; they are footless maggots, with no trace of external organs of any kind. When full grown, the head becomes horny, and it is then pushed out between the segments of the abdomen of the Bee or Wasp, which, by this time, is approaching the perfect state. This is the only change that takes place in the females, which remain in the form of maggots within the body of their victim, with only their heads protruded ; and from this circumstance they were, until very recently, taken for the larvae. With the males, however, the case is widely different. They become converted into inactive pupae, in the interior of the larva- skin, which still remains within the abdomen of the Bee, and finally emerge from their living prison, by pushing off the small horny cap which protrudes between the segments of its body. ORTHOPTERA. 141 They then make their appearance in the form above described, and fly about with great activity in search of their partners ; but their life in the perfect state appears to be very short. The body of the female contains a great number of eggs, and from these, in course of time, a multitude of little, active, hexapod larvce are produced, which escape from the body of their mother by a broad canal running up its lower surface. They run about amongst the hairs of the Bee, and seem, not unfrequently, to take refuge again in the body of their parent. As the Bee visits the flowers in search of nourishment, however, many of the larvae are detached and left behind, when they soon attach themselves to the bodies of other Bees, and are by them conveyed to their nests. Here they bury themselves in the body of the Bee-larva, and become converted into footless maggots. It is the great similarity of this process to what takes place in Meloe (§ 714), that has principally induced modern entomologists to approxi- mate the Strepsiptera and Coleoptera. ORDER II.— ORTHOPTEKA. 724. In many respects the Insects of this Order resemble the Coleoptera ; and they are closely connected with that group by those of the family FORFICULID^E, or Earwigs, which partake of the characters of both. But they differ from the Beetles, in the softer covering of their bodies ; in the partially membranous character of the anterior pair of wings, which seem intermediate between the horny elytra of Beetles and the membranous wings of other insects, and which do not meet when closed along the 142 ORTHOPTERA. central line of the back ; and in the fan-like manner in which the posterior wings are folded up beneath them, which is per- mitted by the straight direction of their veins. They differ also in their metamorphosis ; for, whilst that of the Beetles is com- plete, that of the Orthoptera is only incomplete, — the larva and pupa closely resembling the perfect insect in form, walking and feeding in the same manner, and differing in little else than the absence of the wings and wing-covers, which are gradually and visibly developed in the pupa. — This Order comprises numerous well-known insects, often of large size and splendid colours, such as Grasshoppers, Locusts, and Walking-Leaves ; — as well as Cockroaches and Earwigs. Some of the largest of known insects belong to it ; a few species attaining a length of eight or nine inches, and an equal expansion of wings. Com- paratively few of this Order are inhabitants of temperate regions ; and it attains its greatest development, both as to the number of species and individuals, their size, and their colour, between FIG. 463.— LARVA AND PITPA OF GREAT GREEX GRASSHOPPER. the tropics. All the known Orthoptera are terrestrial, both in their perfect and two previous states. Some are purely carni- vorous, and others are adapted to a mixed diet, — the Cock- roaches, for example, being capable of feeding on almost any kind of organised matter ; but the greater number feed upon plants. Hence from their large size, and the enormous quantity which each individual can devour, they are among the most destructive of all the insect tribes, when they appear in large numbers. This is particularly the case with the Locusts FORFICULHXE, OR EARWIG TRIBE. 143 warm countries ; the ravages of which not unfrequently cause famine and pestilence, both among men and beasts. Some details upon this subject will be given in the latter part of this volume. 725. Before treating of the true Orthoptera, we shall first notice the family FORFICULID.E ; which has been raised by some into a distinct Order, under the name DERMAPTERA, or leathery- winged (§ 695). The Earwigs and their allies, of which this group is composed, have the anterior wings formed into elytra, possessing a consistence intermediate between that of the horny elytra of Beetles, and the parchment-like anterior wings of the Orthoptera ; they are of small size ; and they meet, when closed together, upon the central line, as in Beetles. The posterior wings are folded across when at rest, as in the preceding Order, but the part thus doubled down is itself folded in a fan -like mode, as in the Orthoptera. These insects are further distin- guished by the two large appendages at the posterior part of the body, which form a pair of forceps (Fig. 406). They are very common in damp situations, where they assemble in troops under stones and the bark of trees ; they do much injury to the flowers and fruits of our gardens, and they will devour the bodies of their dead companions. Their forceps appears to serve as an instrument of defence ; whether it answers any other purpose is not known. Their common name is derived from the incorrect notion, that they have a peculiar tendency to creep into the ears of sleeping persons. The female exhibits a great amount of maternal affection, depositing her eggs in a hole in the ground or under a stone or clod of earth, where she watches over them carefully ; nor does her anxiety cease when her young are hatched, for she may be seen accompanying them about, and they have been known to take shelter under her body, like chickens under a hen. 726. The proper Orthoptera may be divided into two prin- cipal sections ; in the first of which the legs are nearly of the same length, and adapted for walking or running, whence they are named CURSORIA ; whilst in the second, the SALTATORIA, the 144 SUBDIVISIONS OF ORTHOPTERA; — BLATTID^E. thighs of the hind-legs are of disproportionate length, and are adapted for leaping. These two groups also differ in the arrangement of the wing-covers and wings, when closed ; for they usually rest horizontally in the body (and consequently more in the manner of those of the Beetles) in the first ; whilst in the second they generally meet at an angle, like the two sides of a roof. The second section is further distinguished by the creaking sound, which the males have usually the power of emitting, by the friction of their legs against the elytra, or of one elytron upon the other. 727. The first section may be divided into three families, which differ considerably from each other in general form, — the BLATTIDJS, 01 Cockroaches ; the MAMTID^E, or Mantis tribe ; and the PHASMID^, or Spectre insects. In the first of these, the legs are adapted for running ; in the second, the fore-legs are converted into claws for seizing the prey ; and in the third, the limbs are adapted only for walking or creeping. — The BLATTIDJE are in many respects intermediate between the Forficulidae and the more typical Orthoptera j in fact, their general resemblance FIG. 464.— BLATTA ORIKNTALIS, MALE AND FEMALE. to the Coleoptera occasions them to be commonly regarded as Beetles. These well-known insects are now pretty gene-rail sm-rally BLATTIDJE, OR COCKROACH TRIBE. 145 diffused over temperate climates; although most of the species are believed to have been originally natives of tropical regions, where only they attain their full development. They are nocturnal in their habits, and active in their movements along the ground ; their powers of flight are usually inconsiderable, the wings being usually small in proportion to the size of their bodies ; and they are extremely voracious, devouring with avidity almost every kind of organised matter. In cold climates the wings are scarcely enough developed, even in the male, to raise the body from the ground ; whilst in the female they are almost entirely absent. The species which is commonest in this country, the Blatta orientalis, is so named from its being supposed to have been originally a native of the East Indies; it has, however, been so long domesticated with us, that its time and mode of introduction are uncertain. In common with most other species of Blatta, it ejects a dark-coloured fluid from the mouth, emitting a very disagreeable odour, of which it is diffi- cult to get rid, and attaching itself to whatever the insect has crept over. The tropical species are larger and more voracious ; one of them, which attains the breadth of six inches when its wings are expanded, is known in the West Indies by the name of drummer, from the sharp knocking sound which it produces, and which is sometimes kept up through a whole night by several individuals replying to each other; and it is said to attack sleeping persons, and even to devour the extremities of the dead. — Notwithstanding the disgusting character which attaches to these insects, on account of their appearance and habits, they present several points of much interest to the Naturalist, especially in regard to their mode of depositing their eggs. Instead of being discharged separately, the ejrgs are col- lected together and deposited at once, enclosed in a large horny case or capsule (equalling half the abdomen of the female in size), and generally of a more or less oval and flattened form, like a small bean with one edge more flattened than the other (Fig. 464, A). Along this edge there is a slit, from end to end of the capsule ; and the plates which form the edges of this slit are jagged or toothed, fitting closely to each other. The interior 146 BLATTID^E. — MANTID^, OR MANTIS TRIBE. of this capsule is divided into two spaces, in each of which is a row of separate chambers, every one of them enclosing an egg. The capsules are attached by means of a glutinous secretion, in such situations as the females select as most fit for their reception ; and the slit part is strongly coated with cement, so as to be even stronger than the other parts. In this capsule, the young larvae are hatched ; and they immediately discharge a fluid, which softens the cement, and enables them to push open the slit ; through this they escape, and the slit then shuts again so closely, that it appears as entire as before. 728. The MANTID.E are purely carnivorous insects, of which none are natives of this country. They differ much from the Blattidae in the form of the body ; which, instead of being flattened and oval, is narrow or compressed, and lengthened. The first pair of legs is enormously elongated, and forms a very powerful organ of attack. These insects frequent trees and plants ; and the forms and colours of their wings and bodies are FIG. 465. — MANTIS, IN THE ACT OF SEIZING A FLY, WITH A YOUNG ONE JUST HATCHED. often so adapted to those of the leaves and twigs which surround them, as to give them remarkable power of eluding observation. Most of the species asume, when lying in wait for their prey, an attitude which has been mistaken by the inhabitants of the countries where they are found, for that of prayer ; and the MANTIS TRIBE. - PHASMID^E, OR SPECTRE INSECTS. 147 names commonly given to the Insects are such as to express this. Thus the best-known species, which is very common in the south of France and Italy (Fig. 465), has received the name of Mantis religiosa, the Praying Mantis, or Soothsayer ; and is termed by the French prie-Dieu. This is regarded by the Turks as an object of superstitious veneration; and many absurd stories are on record, in regard to its habits. The peculiar attitude in question, however, is nothing else than the position in which the prey is most readily seized; — the front of the thorax being elevated, and the two fore-legs being held up together like a pair of arms, prepared to seize any animal that may fall within their reach. These insects are extremely voracious ; and, if kept together without food, they will fight until one is killed, the victor then devouring his conquered adversary. — The eggs are included in a capsule, as in the Blattidae. 729. The third family of the Cursoria, that of PIIASMIDJE, or Spectre Insects, is also restricted to warm climates ; and consists of a small number of extremely curious species, com- monly known under the names of Walking Sticks, Walking- Leaves, &c., from their resemblance to those objects. Their whole structure indicates a sluggish mode of life ; they subsist solely upon vegetables, and crawl slowly among the branches of low shrubs, devouring the young shoots. In fact, their mode of life bears a strong analogy to that of the Sloths among Mammalia. Their means of escape from enemies con- sist entirely in their very close resem- blance to the ob- jects in the midst of which they live. Some of them are destitute of wings, 6 a~ PIG. 466—PHASMA (BACTKRiAl FKAOILTS, OR WALKING-STICK. pearance of dead twigs ; the legs being generally extended in a straight line so as 148 PHASMID2E ; WALKING-LEAF. to look like the lateral twigs ; whilst the absence of motion in the Insect for a long period adds strength to the deception. Others, which possess wings, have still the same general appear- ance ; these organs being laid flat along the back, so as not to extend beyond the body. In others, again, the wings have the form and aspect of withered leaves (Fig. 467) ; whilst the wing-covers are very short. And lastly, there are a few, in which the wing-covers are of a brighter hue, and of larger size, covering in the wings, and giving to the whole animal the appearance of a fresher leaf. These curious insects are for the most part natives of the East Indies, the' East Indian Archi- pelago, Australia, and South America. Their larvae differ but little from the perfect insects, except in their colours and in the absence of wings; and there are several species, as we have seen, in which these are never developed. It not unfrequently happens that they lose a limb by violence ; and this is repro- FIG. 467. — PHYLLTOM SICCIFOLIOM. duced, provided the complete growth of the animal has not been attained. The eggs are laid separately, in the usual manner. 730. The section SALTATORIA consists of numerous species SALTATORIA.— ACHETID^I OR CRICKETS. 149 allied to the well-known Crickets, Grasshoppers, Locusts, &c. ; all of them being adapted, by the peculiar conformation of their hind-legs, to move by leaping rather than by running. Besides this peculiarity, they all agree in depositing their eggs in the ground: and they frequently effect this by means of a horny tubular prolongation of the last segment of the body, or oviposi- tor, such as we shall meet with in the order Hymenoptera. There are three distinct groups in this section; — namely, the ACHETIDJE or Crickets; the GRYLLIDJS or Grasshoppers; and the LOCUSTID^E or Locusts. In the ACHETHXE: or Crickets, forming the first of these families, the antenna are long, slender, and tapering, and the elytra are laid flat upon the back in repose. The tarsi are composed of three joints, and the abdomen bears at its extremity a pair of bristle-shaped appendages. The females are usually furnished with a slender ovipositor, but this is wanting in some species. The stridulation of these Insects is effected by means of peculiar talc-like spots, surrounded by strong veins and placed near the base of each elytron ; it is by the rapid passage of these over each other that the sound is produced. The Crickets are essentially inhabitants of the ground, in which many of them burrow, both in the larva and perfect states ; few of them have any powers of active flight. One of the most im- portant species of this family is the Gryllotalpa vulgaris, or Mole- Cricket (Fig. 400), which derives its name from the pecu- liar similarity in its anterior extremities, and from the resem- blance in its habits, to those of the Mole. It is about an inch and a half long, and of a brown colour. In making its burrows, it cuts through or detaches all the roots of plants which it en- counters ; but it does not do this so much for the purpose of feeding upon them, as to make a passage in search of insects and worms. The female forms, in June and July, at the depth of about six inches from the surface, a rounded cell, smooth within, and resembling with its gallery a bottle with a long bent neck ; in this she deposits from 200 to 400 eggs ; and the young remain in society for some time after they are hatched. The larva? are at first white ; but in other respects they resemble their parents, except in their smaller size and their want of wings , after their VOL. II. M 150 CRICKETS ; — GRASSHOPPERS. FIG. 468.— HOUSE-CRICKET. first moulting, they disperse, and soon gain their darker colours ; and they are about three years before they arrive at the perfect state. Their wings are so little developed, that the possibility of the flight of the insects has been denied. It is remarkable that the various species of this singular genus should be spread over the whole globe. The House- Cricket (Fig. 468) is too well known to require particular description ; it takes up its abode in the neighbourhood of the fire-places of rooms on the ground- floor, sometimes burrowing into the mortar, even within a few inches of the fiercest fires ; and here it remains during the winter months, be- coming torpid in its haunts, if the fire be discontinued. In the summer, however, it fre- quently goes forth to the gardens, and seeks a habitation in the crevices of garden-walls, &c., as if it then found heat enough out of doors. The Field- Cricket is much larger, and also rarer, than the preceding ; it frequents hot sandy dis- tricts, in which it forms its burrow at the side of footpaths, &c., in situations exposed to the sun, to the depth of from six to twelve inches ; and sits at its mouth watching for its prey, which is said to consist of other insects. This is one of the most noisy of all the Crickets. 731. TheGryllida, or Grasshoppers, are ^ distinguished from the fe^c: ~ — •* --v*/^1 r >. * preceding by the roof- "^^^^a?^ —€~? -C^Ls-—'--'- like position of the wing-covers, which in the Crickets fold horizontally ; but agi with them in having long thread-like antennas, and a talc-like spot at the base of the wing-covers in the males. They are dis- GRASSHOPPERS. — LOCUSTS. 151 tinguished, on the other hand, from the Locusts, with which they agree in the first of these characters, by the inferior robustness of the body, and the length and slenderness of the legs and an- tennae. They differ from both, in having the tarsi composed of four joints. The Gryllus viridissimus, or Great Green Grass- hopper, represented in Fig. 469, is the largest British species of this Order, and one of the largest of our native insects ; its length being about two inches, and its breadth, when the wings are expanded, being three inches and a half. Many species of this family are destitute of wings, or have only small wing-covers. Of their voracity a curious instance is mentioned by Mr. West- wood ; who states that on one occasion he placed a specimen of the large green species in a box, together with one of its legs which it had accidentally jerked off; and on opening the box the next morning, half the leg was devoured. Amongst the foreign species of this group, there are some which bear a most singular resemblance to the fresh leaves of various plants. 732. The last group of this Order consists of the various tribes of mi- gratory Locusts, together with several which are ordinarily ranked as Grasshoppers, but which agree with the Locusts in the shortness of their antennae, and the robust- ness of their bodies and limbs (Fig. 470). Their elytra are destitute of the talc-like spots characte- ristic of the two preceding groups, and their stridu- lation is effected by the friction of the inside of the thighs against the veins of the elytra, tarsi consist of three joints ; and the abdomen of the female destitute of an ovipositor. They leap with much greater FIG. 470.— Locrsr. 152 PHYSOPODA. energy than the preceding, and have a much longer-sustained flight. The powers of devastation possessed by the Locusts are almost inconceivable ; for they are produced in vast numbers, and live in societies, so as speedily to destroy the vegetation of the spot on which they have settled. Thence they take their flight in vast multitudes to adjoining districts ; and so great is the number of which these swarms consist, that it is not speaking figuratively to say that the sky is darkened by their passage. Their ravages usually continue until they are checked for want of a further supply of food ; for as the instinct of the Locusts leads them to continue their flight in the same direction, they are at last stopped either by the desert or the sea ; and some- times a storm, carrying them out of their course, or hurrying them on in it, effects a clearance much more speedily than any other cause could do. Of the cause of the occasional appearance of the Locusts, in such vast multitudes, no satisfactory explana- tion has been given. Of these Insects there are several different species, which are distributed over the tropical and the warmer temperate regions of the globe ; and in many parts they are used as food by the inhabitants of the countries they infest. ORDER III.— PHYSOPODA. 733. The small order of the PHYSOPODA includes some minute insects which were placed with the Rhynchota byLinnasus and the older Entomologists, in consequence of their mouths being drawn out very much in the form of a rostrum. They are, however, more nearly allied to the Orthoptera, although they are at once distinguished from those insects by the weak- ness of the organs of the mouth. As in the Orthoptera, the metamorphosis is incomplete. The wings, which are usually four in number, are flat and generally very narrow, but fringed, sometimes all round, sometimes only at the apex, with long delicate hairs. The antennas generally consist of about eight joints, and are situated on the front of the head between the PHYSOPODA. — NEUROPTERA. 153 eyes ; the latter are of moderate size, and granular in their ap- pearance ; and between them, on the crown of the head, there are generally three ocelli. The legs are of moderate size, and terminated by two-jointed tarsi ; the second joint bears no claws, but is furnished with a soft vesicular pad, which enables the insects to cling firmly to any object on which they may be walking. These insects are nearly all of minute size, rarely exceeding an eighth of an inch in length ; one or two Australian species, however, are larger ; the Idolothrips spectrum measuring about a third of an inch long. They run actively, and some of them are able to leap to a considerable comparative height by means of their abdomen, which they employ in the same way that the Podurce do their furcate caudal appendage (§ 803). 734. They are herbivorous in their habits, and are generally found in the flowers of plants, where, from their slender forms and dark colours, most of them appear like little moving lines. Some species live upon the stems and leaves of plants, to which they often do considerable injury. This is the case with the Thrips cerealium, which attacks the wheat crops, either gnawing the stems when tender, or destroying the flowers and young grain. According to an Italian writer, the whole wheat crop of Piedmont was destroyed by this insect in the year 1805. A few species also live under the bark of trees and in rotten wood. ORDER IV.— NEUROPTERA. 735. The Neuroptera, like the Coleoptera and Orthoptera, have a mouth adapted for mastication, but differ from them as to the conformation of the wings ; the anterior as well as the poste- rior pairs being here membranous and usually transparent. In both pairs of wings, the veins form a very beautiful and minute network, subdividing and uniting again, so as to divide the whole surface into a large number of minute cells, which much exceed in number those of the wings of any other tribe of insects (Fig. 471). Although the posterior wings are usually as large 154 NEUROPTERA. as the anterior, or sometimes even larger, they are occasionally much smaller, and may even be altogether wanting. 736. The body of the Insects of this Order, which contains the well-known Dragon-flies, May-flies, Ant-lions, White Ants or Termites, and others, is generally prolonged, and destitute of any very hard integument. These insects are of intermediate size : few of them exceeding in dimensions the largest Dragon- flies of this country ; whilst none exhibit the minuteness of some Hymenoptera and Coleoptera. They differ in the character of their metamorphosis, as well as in their adult structure ; for in some the metamorphosis is complete, the larva undergoing a marked change of form ; and in others there is not much differ- ence, except in the absence of wings, between the larva and perfect insect. By these differences the Order may be divided into two sections ; in the first of which the insect is active during the whole of its pupa state ; whilst in the second, it is quiescent, except just before its last metamorphosis. The first of these groups may again be subdivided into five families ; — the LIBELLULIDJE or Dragon-Jlies ; — the EPHEMERID.E or Day-flies; thePERLHXE or Stone-flies ; the TERMITID^: or White Ants; and the PSOCID^E or Book-lice. In the first three of these, the larvae and pupas are inhabitants of the water, and respire by means of peculiar organs placed along the sides or at the extremity of the abdomen ; whilst in other respects they nearly resemble the per- fect insect. They creep out of the water to undergo the final metamorphosis. 737. Section I. The LIBELLULID^E, or Dragon-flies, are well- known insects ; being easily distinguished by the slender form of their bodies, their varied colours, their large gauze-like wings, and the rapidity of flight with which they pursue other insects on which they prey. They have a large head, ot rounded form, fur- nished at its sides with two very large compound eyes, and with three ocelli, situated upon its upper surface. Their antennas are very small and bristle-shaped ; and the organs of their mouths large and powerful. Most of this tribe frequent the neighbour- hood of water ; and may be frequently seen skimming over the surface of ponds or streams, in search of flies, gnats, and other LIBELLULID^E, OR DRAGON-FLIES. 155 small insects. The eggs are deposited upon aquatic plants, and the larvae are thus produced in the element in which they are at first to reside. The head of the pupa is remarkable for the singu- lar form of the portion which takes the place of the lower lip; this FIG. 471.— LIBELLULA CANCELLATA. is a kind of mask, composed of several pieces, and covering the mandibles, maxilla?, and nearly all the under side of the head, when it is closed together ; but being capable of extension and unfold- ing, and being furnished with a pair of sharp claws at its upper part, so as to become the instrument by which the animal seizes its prey. The posterior end of the abdomen, in the early state of the Dragon-flies, is usually the seat of the respiratory function. This is performed by means of three leaf-like membranous or- gans, which are situated at the extremity of the abdomen, or by the agency of tufted branchiae placed in the interior of the terminal portion of the intestine. In the latter case the animal draws a Supply of water into the rectum, and then forces it out violently, by which act it also impels itself through the water. The suc- cession of jerks thus produced, is the chief means of locomotion of the larvae of many of the Dragon-flies, and serves to distin- guish them from all other aquatic larvae ; so that they are very easily recognised (Fig. 472). Several species of Dragon-flies 156 AGRIONS ;— EPHEMERIDJE, OR DAY-FLIES. exist in this country ; the largest, which is surpassed in size by few others, measures two inches and a half in length ; but the FIG. 472 — A, the pupa with its mask. B, the same with the mask closed, and discharging a current of water. j. foreign species are usually more brilliantly coloured. — In the Agrions, the wings stand perpendicularly when in repose, instead of horizontally as in the Dragon-flies ; and the mouth is some- what differently constructed. The species represented in the accompanying figure is of a golden-green, or bluish- green colour, with the wings blue ; and, in common with many other less conspicuous species, it is an inhabitant of Britain. 738. The EPHEMERID^E, or Day-flies, receive their name from the short duration of their lives in the perfect state. The history of their early condition has been already given (§ 690). Their last change takes place near sunset on the fine days of summer and autumn ; and they are sometimes produced in such vast numbers at one time, that the ground is covered with them FIG. 473.— AGRION VIRGO. PERLID^E, OR STONE-FLIES. 157 after their death, and their bodies are carted away as manure. They take no food after their final change ; and as the propaga- tion of the race is then their only object, they die almost as soon as it has been performed, often in a few hours afttr they have PIG. 474.— EPHKMEHA. quitted the water, — the duration of their lives in their previous conditions having been two or even three years. Like the Dra- gon-flies, they have minute bristle-shaped antenna?, but the parts of the mouth are rudimentary, and the extremity of the abdomen is furnished with two or three long tails. 739. The PERLID^:, or Stone-flies, resemble the preceding in the possession of long bristles at the tail, and to a certain extent in the imperfect nature of the buccal organs ; their larvae also are aquatic, and respire by the agency of branchial organs at- tached to the sides of the thorax and abdomen. But the long tails of the Stone-flies are jointed appendages ; the antenna? are long and filiform ; and the posterior wings, instead of being smaller than the anterior pair, are considerably larger. The common Stone-fly is found in plenty in most of our fresh waters, and is much used as a bait by anglers, as is also its larva, which closely resembles the perfect insect, and is commonly known as the Water-cricket. An American species, described by the late Mr. Newport, retains its branchial appendages even in the per- fect state ; and the habits of this insect appear to be peculiarly aquatic. 740. The TERMITID^E, or White Ants> are terrestrial, active, and carnivorous or omnivorous, during all their stages. They are easily distinguished from the Dragon-flies and Day-flies by their filiform antenna? ; and from the Stone-flies by the want of 158 TERMITES, OR WHITE ANTS. the caudal filaments. In several points of their structure, they resemble the Orthoptera ; whilst in their habit of living in socie- ties, they resemble a large proportion of the Hymenoptera. There is, however, as we shall hereafter see, a considerable dif- ference in the duties of the several tribes of which these commu- nities consist. A more particular account of their operations will be given in a later part of this volume ; and at present it will be sufficient to say, that the larvae resemble the perfect in- sect, except in the absence of wings, and are the workers. Among the adult insects there are some, which never acquire wings, and in which the reproductive organs are not developed ; these, which are termed the soldiers (Fig. 475), have the head much larger and longer than that of the larvae, and the mandibles are very long and cross each other ; they are far less numerous than the larvae, and live near the outer surface of the nest, so that they are the first to make their appearance when it is attacked ; and they are also stated to compel the workers to labour. The FIG. 475.— SOLDIER TERMES. FIG. 476.— TERMES in perfect state. FIG. 477.— QUEEX in the winged state, and filled •with Eggs. winged males (Fig. 476) and females, when they have arrived at their perfect state, quit their habitation, and fly abroad during TERMITID.E ;— MYRMELEONIDJE, OR ANT-LIONS. 159 FIG. 478. — ATROPOS PULSATORITJS. the evening or tne night, in great numbers ; they lose their wings before the morning, however ; and the greater part of them, falling to the ground, become the prey of birds, reptiles, &c. The females, however, are sought by the workers, who imprison them in royal chambers, as they have been termed, in the centre of the nest. The abdomen subsequently attains an enormous size, from the quantity of eggs it contains ; and these, when laid, are carefully tended by the workers, and defended by the soldiers. 741. The little family of the PSOCID^E, or Book-lice, includes a few minute species nearly allied to the Termites, with which they were formerly arranged in one family. They are distin- guished by having their tarsi composed of only two or three joints, and their posterior wings smaller than the anterior ones. They usually live in dark damp places, and under bark. One species, which is destitute of wings (Fig. 478), is found very commonly in old books, and in collections of dried plants, insects, &c. It is said to be capable of producing a sound like the tick- ing of a watch, for which reason the name of the Death-watch is sometimes given to it. The true Death-watch, as already stated, is a species of Beetle (§ 712). 742. Section II. Of the division of Neuroptera in which a more complete metamor- phosis occurs, the pupa passing into an inactive condition, the family of MYRMELEONID./E, or Ant-lions, distinguished by their clavate antennae, which are generally ra- ther short, is one of the most remarkable. As the peculiar habits of the Ant-lion in the larva state have already been described (ANIM. PIIYSIOL. § 697), they need not be here dwelt on. When the FIG. 479.— MYRMF.LEO. 160 HEMEROBtJDJE. — SIALID^E. larva has attained its full growth, and is ready to assume the pupa state, it spins a perfectly round cocoon of a silky matter, the exterior of which it covers with sand ; and from this the perfect insect makes its escape at the end of fifteen or twenty days. None of this group are found in Britain. 743. The family HEMEROBIID^E, which is closely allied to the preceding, but readily distinguished therefrom by its thread- shaped antennae, is remarkable for the exceeding brilliancy of the eyes in most of the species, and for the delicate structure and varied colour of the wings. The eyes often resemble the most highly-polished gold ; and the wings frequently reflect the prismatic colours ; so that, although of small size, these insects are very conspicuous. They are for the most part inhabitants of temperate climates ; and many species abound in Britain. They usually fly during the twilight, remaining inactive during the day ; and they emit a very disagreeable odour when handled. The females deposit their eggs upon plants, attaching them at the extremity of a long slender footstalk, the base of which is fastened to the leaf ; this footstalk is composed of a white viscid matter, discharged by the female at the time of laying her egg, and speedily hardening by exposure to the air. The eggs, thus curiously fixed in small clusters, have the appearance of minute fungi. The larvae are extremely voracious, and especially attack the Aphides ; unlike the Ant-lions, however, these Aphis-lions (as they have been termed) do not remain concealed in one spot, but wander in search of their prey where it is to be found in the greatest abundance. So ravenous are they, that they do not require more than half a minute to suck the juices from one of the largest Aphides ; and they not unfrequently attack each other, the conqueror in like manner sucking the body of the vanquished. During the summer they arrive at their full growth in about fifteen days ; they then spin a silken cocoon, in which they remain as inactive pupaa during the winter; and come forth in the succeeding summer. 744. The remaining families of this Order may be very briefly noticed. The SIALID,E are a small group of moderate or large-sized Neuroptera, having very large anterior wings. They PANORPID^E. 161 are nevertheless slow and inactive in their habits, and frequent the neighbourhood of water, in which they pass their larva state. The ordinary species, Sialis lutaria, or May-fly, is a well-known bait with the angler, being produced during the spring months in large quantities ; it is of a dull brown colour, and may be found on the walls or palings near the water. The larva is fur- nished with appendages for aquatic respiration, strongly resem- bling those of the Ephemera ; but when arrived at its full growth, it quits the water and burrows into the adjoining bank, in which it excavates a sort of cell. Here it is transformed into a pupa, which remains inactive, with its limbs laid along the breast, but which is lively when disturbed ; and here, too, it undergoes its final change. 745. The PANORPID.ZE are distinguished by having the head produced downwards into a rostrum. The common British species are known under the name of Scorpion-flies, on account of the remarkable conformation of the posterior extremity of the abdomen in the male. The sixth and seventh seg- ments are very slender and somewhat curved upwards, so as to constitute a sort of tail ; whilst the eighth is greatly thickened, forming an oval mass, armed with a pair of forceps, and capable of *'~™P' free motion in an7 direction. The species represented in Fig. 480 is a very common British insect, frequenting hedges and woods. The Scorpion- flies are very active, and prey upon other insects in the perfect state. The abdomen of the female is also prolonged so as to form an ovipositor ; by which she can deposit her eggs in deep holes or crevices. In the curious foreign genus Nemoptera, some species of which are found in the southern countries of Europe, the anterior wings are broad and rounded, and the posterior pair are greatly elongated and very narrow, but terminated by a broad dilatation. In Boreus, another singular genus of this family,' the wings are wanting, or represented only by peculiar append- ages ; this insect is also remarkable for its habits, as it is always found in the depth of winter, hopping about upon the snow. 162 RAPHIDIID^E. — M ANTISPID^E. — PHRYGANEID^. 746. The RAPHIDIHXE are commonly known as Snake-flies, from the elongated form of the head and neck, and the facility with which they move the front of the body in different direc- tions. They are of comparatively small size, agile in their movements, and possessing powerful jaws ; they are chiefly found in the neighbourhood of woods and streams; and they prey upon other insects inhabiting the same situations. — Finally, the MANTISPID^: seem to connect this order with the preceding ; having the mouth formed upon the plan of that of the Neurop- tera ; but having the fore-legs converted into prehensile claws, and the first segment of the thorax lengthened so as to elevate them, almost exactly as in the Mantis. 747. We shall next mention the small intermediate group of PHRYGANEIDVE, or Caddice-flies, which are by some entomolo- gists regarded as constituting an aberrant family of the Neu- roptera, whilst others raise them into the rank of a distinct Order, TRICHOPTERA, — a name derived from the hairy covering with which their wings, as well as their bodies, are beset. In this character, as also in the arrangement of the nerves of the wings, they bear a certain resemblance to the Lepidoptera. 748. These Insects are chiefly remarkable on account of the habits of the larvae, which are well known under the name of Caddice-worms. These reside in cylindrical cases, open at B each end, to which they attach various matters, as bits of stick, weeds, pebbles, or even small living shells, by the assistance of silken threads, which they spin from the mouth. These cases they bear about with them ; protruding the three first segments, with their legs, when they creep forwards ; and withdrawing these upon the slightest alarm. They are never known to quit these cases of their own accord. Different species appear to prefer different ma- FIG. 481.— PHRYGANEA GRAXDIS.— A, Larva in its case ;B, grating ; c, Imago. HYMENOPTERA. 163 terials for the construction of their cases ; but they have the power of employing almost any which fall in their way, when there is a deficiency of those usually preferred. The food of some of the larvce is vegetable ; but others prey upon small aquatic larvse, such as those of the Neuroptera. — When about to assume the pupa state, the larvae fix their cases to some solid substances beneath the water, and close the two extremities with a kind of grating, that admits of the passage of water through the tube, which is necessary for respiration. A short time before they are to assume their perfect form, they make their way out by means of the pair of hooked jaws, with which they are then furnished, and swim about with great activity by means of the two hind legs, crawling occasionally upon the four first. In order to throw off their pupa-case, the larger species crawl up plants out of the water ; but the smaller ones merely come to the surface, and there undergo their transformation, — using their old envelope as a boat, out of which they rise to expand their wings, much in the same manner as Gnats. The perfect Caddice-flies run with great agility, but their flight is awkward, — except in some of the smaller species, which assemble in troops and fly over the surface of the water towards sunset. They are nocturnal in their habits, and not unfrequently enter our houses, being attracted by the light. They emit a disagreeable smell when touched. These insects are very numerous in Britain ; no fewer than 190 species having been described. ORDER V.— HYMENOPTERA. 749. In the membranous character of their four wings, the insects of this Order resemble the Neuroptera ; but they cannot well be mistaken for them. The anterior wings are usually much larger than the posterior ; and the veins or nerves * are * These terms are used to mean the same things; namely, the hard frame- work on which the membrane of the wing is extended. They must not be un- derstood as indicating any analogy to the veins and nerves of higher animals. 164 INSTINCTS OF HYMENOPTERA. much fewer in number than in the Neuroptera, and do not form a close network by their ramifications, as in that Order. In some of the minute species, the wings are almost, or even en- tirely, destitute of nerves. Another character furnished by the wings consists in the connection of the anterior and posterior wings on each side, during flight, by means of a series of minute hooks along the front edge of the latter, which catch the hinder margin of the other, so as to produce one continued surface on each side. The Hymenoptera are also peculiarly distinguished by a prolongation of the last segment of the body in the females, into an organ, — which is, in one division of the Order, a sting, — and in the other, an ovipositor, or instrument for the deposi- tion of the eggs, usually possessing the power of boring a hollow for their reception (§ 667). 750. The Hymenoptera are further remarkable for the great development of their instinctive faculties, and of their locomotive powers. It is in this Order that we find the most remarkable examples of contrivance, and of skilful adaptation of means to ends ; but this adaptation results, it would appear, not from an exercise of intelligence on the part of the animals themselves (as in Man and the higher Vertebrata), but from their blindly fol- lowing out a path laid down for them by the Almighty Designer (ANIM. PHYSIOL. § 475). That the two classes of faculties just mentioned should attain their highest development in the same group (the Neuroptera may, perhaps, be included in this state- ment), is a very remarkable and interesting fact. Considering these powers as those which are peculiarly characteristic of the animal kingdom, we may regard these groups of Insects as the types or centres (§ 35) of that kingdom. As we descend the scale, we find these powers gradually disappearing, whilst, the organs of vegetative life (which, as we have seen, are of compa- ratively small size in Insects), gain the predominance, so that in the Zoophytes we have an evident approach to the vegetable kingdom. On the other hand, as we ascend the Vertebrated series, we find the Instincts gradually superseded by Intelligence, which in Man becomes the sole director (at least in the well- governed mind) of the actions, keeping the instincts in subordi- METAMORPHOSIS OF HYMENOPTERA. 165 nation ; and through his immortal soul we are connected with that kingdom of pure Intelligence, in which we have reason to believe that Mind exists unfettered by the imperfections of its corporeal instruments, and of which we are encouraged to hope that we shall ourselves be sharers, when " this corruptible shall have put on incorruption." — The mutual adjustment of the various instinctive actions of a large number of individuals, so that they all work together towards a common end, like the parts of a machine, is nowhere so remarkable as in the social Insects, which are principally restricted to this Order ; and the Bees, Wasps, and Ants belonging to it, have consequently at- tracted the attention of the observer of nature from a very early period. 75 1 . The Insects of this Order undergo a complete meta- morphosis ; the larvae being more imperfect than those of almost any other tribe ; and the pupae being quite inactive. In the greater proportion of the Order the larvae are destitute of feet, and resemble little worms. Their support is provided for, either by the deposition of the eggs in situations where the future grub will be furnished with an ample supply of food — the parent being directed to these by an unerring instinct, — or by the active exertions of the parents, which convey to the young the food which they have themselves collected ; or by similar exertions on the part of a race destitute of peculiar sex (hence termed neuters), on whom this charge more especially devolves. When FIG. 482.— LARV.E OP BEE, NATURAL FIG. 483.— PUPA OP BEE. SIZE, AND MAGNIFIED. arrived at their full growth, and after undergoing several pre- vious changes of skin, the larvae are transformed into inactive pupae ; in which all the limbs of the future insect are visible, encased in distinct sheaths, and folded on the under surface of VOL. n, N 166 CLASSIFICATION OF HYMEXOPTERA. the thorax. During this part of their existence they take no food. In their perfect state, these insects, for the most part, take but little nourishment ; and this consists almost exclusively of the nectar of flowers. Many of them, however, — such as the Wasps, — attack and destroy other insects ; but these are often destined, not for their own support, but for the nourishment of the young. — This Order is of considerable extent, being inferior only to the Coleoptera ; and it has been estimated to contain one-fourth part of the whole Insect population. It attains its greatest development in warm climates ; for, of the numerous species inhabiting this country, the greater part are of very small size, and some are almost of even microscopic minuteness. None of the species attain any great dimensions ; very few of them exceeding, or even attaining, two inches in length, or three in the expansion of their wings. The duration of their lives, from the hatching of the egg to the final change, is believed never to exceed a year. 752. This Order may be primarily divided into two groups, according to the nature of the organ in which the body of the female terminates ; — the end of the abdomen being prolonged, in the TEREBRANTIA, into a saw or borer for the deposition of the eggs ; whilst, in the ACULEATA, it is formed into a sting or piercer connected with a poison -reservoir.* In the former group the number of joints in the antennae is very variable ; whilst in the latter, it is almost always twelve in the female, and thir- teen in the male. The Terebrantia may be again divided into the SECURIFERA, in which the abdomen is attached by its whole breadth to the thorax, of which the larvse feed upon vegetable matter; and the ENTOMOPHAGA, distinguished by having the abdomen supported upon a foot-stalk, in which the larvae gen- erally feed parasitically upon living insects. The Aculeata are in like manner divided into the PR^EDONES, or predaceous tribes, which do not collect pollen, and in which the larvae feed upon * The reader must bear in mind, however, that the sting and the ovipositor are essentially the same organs ; the ovipositor of the Entomophagous Tere- brantia, and the sting of the Aculeata, being almost identical in their construc- tion. TENTHREDINIDvE, OR SAW-FLIES. 167 other insects stored up for them, or upon fluids collected by the neuters ; and the MELLIFERA, in which the larvae feed upon honey or pollen-paste, collected and stored up for them. All these have characteristic distinctions in their adult form ; on which it would not be accordant with the character of this work to dwell minutely. The division of the Order into sections may be better understood from the following tabular arrangement of them : — (Larva vegetable- .l feeders I. SECURIFERA. ' Larvae parasitic II. ENTOMOPHAGA. f Predaceous in habits III. PR^EDONES. (Honey -collectors IV. MELLIFERA. Armed with sting — ACULEATA 753. Section I. TEREBRANTIA SECURIFERA. The principal family of this section is that of TENTHREDINID^E, or Saw-flies, so named from the saw-like character and action of the ovipositor. With this instrument they make a succession of small holes in the branches or other parts of trees, into each of which they insert an egg, closing the hole with a drop of frothy fluid. The tissue in the neighbourhood of the wound swells up from its irritation ; and sometimes be- comes a kind of gall, either woody or pulpy, according to the parts injured, which forms the abode of the larva in some cases, during its whole life as such, and up to its (final metamorphosis ; but in general the larva? come forth at an Earlier period, and feed upon the exterior of the leaves. They greatly resemble the Caterpillars of Lepidopterous insects ; but usually differ from them as to the number of their feet, which are either restricted to six, answering to those of the perfect insect, or amount to eighteen or twenty-two. In order to undergo their FIG. 484. — A, extremity of the abdomen of the Saw-fly, showing the two saws, c, and their supporters, d, ex- tended ; «, the terminal joint of the abdomen ; and b, the two internal horny sheaths. B, a small portion of one of the saws very highly magnified. 168 TENTHREDINIDJE ; TURNIP-FLY. change into the pupa state, they spin a cocoon, either in the earth or on the plants on which they have fed ; but they do not become pupse, until they have been inclosed in this for many months, and only a few days before they come forth as perfect Saw-flies. To this group belongs the Athalia centifolice, or Turnip-fly, which occasionally appears in this country in such vast numbers as to produce the greatest devastation. The larva is twenty-two-footed, and of a greenish-black colour ; whence it is commonly known by the appellation of the nigger, or black caterpillar of the Turnip, — to which plant it is chiefly detrimen- tal, by devouring the leaves, and thus totally destroying the crop in an incredibly short space of time. It was especially abundant in the south-eastern counties of England, in the years 1835, 1836, and 1837. The appearance of the black larvse is preceded by that of the imago, a pretty yellow and black insect, which is first seen hovering over the turnip-fields about the middle of May or the beginning of June ; it deposits its eggs in the soft tissue of the leaf, puncturing the cuticle by its ovipo- sitor ; and these are hatched in five or six days. In a few days more, a whole field has been often devastated by the voracity of the larvsa, which devour the soft tissue of the leaves, leaving only their skeletons and stalks. The most effectual remedy for these attacks was found to be the introduction of Ducks into the fields, by which the plants were cleared of the larvas more effectually than they could be by any other means. Many other species exist, however, almost equally injurious to different tribes of plants. Thus the Gooseberry is subject to the attacks of a Tenthredo, of which the larvse — often amounting to as many as one thousand upon a single tree — devour its leaves at the begin- ning of summer. The Apple, again, suffers from the deposition of the eggs of another species in its fruit. And the Willow is subject to the attacks of many species, some of which devour its leaves, whilst others cause the production of galls by perforating its branches. The perfect Insects of this group are of moderate size, not exceeding an inch in length ; some of them, however, are among the largest Hymenoptera inhabiting this country. Their flight is usually heavy, and is attended in the larger spe- cies with a humming noise ; they seem, however, to be more TENTHREDINID.E, OR SAW-FLIES. — SIRICID^E. 169 agile in the hot sunshine. They come forth for the most part in the spring, having passed the winter in the pupa state ; and they usually obtain their chief supply of food from the pollen or honey of flowers, especially those of the Umbelliferous tribe ; some of them, however, attack and devour living insects which frequent the same plants. The ravages of these insects are restrained by the destruction of vast multitudes of their larvae, through the agency of the Entomophagous or parasitic section of this group ; thus the Lophyrus pi?ii, a Saw-fly which infests the Pine, is it- self subject to the attacks of at least twenty parasites, of which fifteen are Ichneumonidse. 754. The SIRICID^E bear a strong general resemblance to the preceding group, both in structure and habits ; but they have a stronger ovipositor, agreeing in structure with that of the Ento- mophagous section, which enables them to pierce not merely the soft substance of leaves or young shoots, but hard timber. The larvae produced from the eggs thus deposited, usually reside in the interior of trees, which they perforate in various directions ; often causing great destruction in the Pine forests, of which the largest species are inhabitants. When full grown, they form a slender silkon cocoon, mixed with chips of wood, at the ^.%s^ extremity of the >v s burrow ; and here they undergo their final transformation. ^^ The perfect Insects are among the largest of the Order ; they are remarkable for the very cylindrical form of their bodies, and for the hum- ming sound which they make when on PIG.485.-SIKEX GIGAS. the wing> 755. SECTION II. — In the section of TEREBRANTIA ENTOMO- PHAGA, the first family, that of CYNIPID.E, or Gall-flies, rather 170 CYXIPID.E, OR GALL-FLIES. corresponds with the preceding in its general habits, and in the diet of the larvae. These insects puncture, with their ovipositor, the surface of the leaves, buds, stalks, and young stems and roots, of various plants and trees ; and they increase the aperture by means of the toothed edge, forming a kind of saw, with which the extremity of this organ is armed. In this aperture they deposit, besides the egg, a drop of fluid, which seems to be peculiarly irritating in its character ; causing the production of tumours or galls, of various sizes, shapes, and colours ; the solid interior of which becomes the food of the larva when hatched. It is a remarkable circumstance, that the very same tree should produce, on its different parts, galls of very different forms and of various degrees of consistency, according to the species of Cynips by which it has been punctured. The hardest is the common Gall-nut, which is employed in the manufacture of ink, and also, to a far greater extent, in the process of dyeing black 'VEGET. PHYSIOL. § 399). This is produced in the Levant, upon a low-growing species of Oak, the Quercus infectoria. It has been recently ascertained that the " apples of Sodom,"- which are found on the borders of the Dead Sea, and which have been said " to appear outwardly tempting to the eye, but to turn to ashes on the lips," — are nothing else than galls of a softer consistence, produced from the same Oak by the attacks of an- other species of Cynips. The " oak-apples " of our own country are large galls found upon the young shoots of the Oak ; the leaves sometimes produce, besides larger galls, a multitude of little spangled discs, of a reddish colour, which contain the Iarva3 of a small species of Cynips ; the parts of fructification are sometimes attacked by a species, the galls of which hang on the catkins like a bunch of currants ; and the root produces a large woody gall, inhabited by a species of Cynips, of which 1100 individuals have been found in a single gall. The Oak is by no means the only species of vegetable infected by these insects ; but a larger number of Gall-flies appear to be restricted to it than to any other plant. The Rose is subject to the attacks of one species, which causes the flower-bud to be developed into a gall in a very curious manner. — An insect, considered as belong- GALL-FLIES. — ICHNliU.MONlDJE. *163 ing to this family, deposits its eggs in the seeds of the most forward wild figs of the Levant. The modern Greeks, following a custom handed down to them by their forefathers, fasten sever- al of these fruits among the later figs ; and the insects escaping from them, covered with pollen, make their way into the unfer- tilised fruit, and thus contribute to its maturity (BOTANY, § 673). This operation is termed caprification. The larvae of some of the species are parasitic upon other insects. 756. The family of ICHNEUMONID^E may be regarded as pe- culiarly characteristic of the Entomophagous section. The female Ichneumon deposits her eggs, by means of her sharp-pointed ovipositor, only in the bodies of other insects, — chiefly the cater- pillars of Lepidoptera, or the larvae of the Phytophagous section of Ilymenoptera. Some of them have a very long ovipositor, which is used to insert the eggs into the bodies of Caterpillars that live beneath the bark, or in the crevices of wood ; whilst those in which this instrument is short, place their eggs in or upon the bodies of caterpillars, to which they can obtain easier access. They do not confine themselves to these situations, how- ever ; but employ for the same purpose the eggs or pupae, or even the perfect Insects, although most of them prefer the larvae. The young Ichneumons, when hatched as footless grubs, — some- times in considerable numbers in the body of one caterpillar, — devour only the fatty parts, which are not absolutely essential to life ; and the animal they infest may continue to exist for some time, thus affording them a continued supply of nutriment ; but when the Ichneumons are ready to undergo their last meta- morphosis, they either pierce the skin and escape, or else they kill their victim, and perform their changes within its body. The perfect Ichneumons feed solely upon the juices of flowers, and fly about with considerable agility in search of their nutri- ment, or of proper situations for the deposition of their eggs. It is in the genus Pimpla, that the ovipositor attains its greatest development, its length being in some exotic species as much as three or four inches ; when not in use, it is inclosed in two long channeled filaments, which unite to receive it like a sheath. 164' ICHNEUMONID.E. — CHALCIDIDJE. FIG. 486 PIMPLA. MANIPESTATOR, DEPOSITING ITS EGGS. This family is extremely numerous. Probably more than 3000 species exist in Europe alone ; and the number peculiar to other parts of the globe may fairly be reckoned as at least equal. Scarcely any tribe of Insects is free from their attacks ; although, as al- ready stated, the Lepidoptera are the chief suf- ferers. In re- straining the multiplication of many Insects, which commit great injury against the Agriculturist, the Ich- neumonidae render essential service to Man ; and there is no mode in which they can be said to do him any counteracting injury. 757. The family CHALCIDID.E, or Chalets tribe, is composed of a great number of parasitic insects, distinguished by their generally very minute size (their length seldom exceeding a line or two), their brilliant metallic or variegated colours, and their nearly veinless wings. Like the Ichneumonidae, they are all parasitic upon other insects in their early states ; the majority infesting the larvas and pupse ; but some, from their minute size, being reared within the eggs of other insects. They are especially destructive to Lepidoptera ; but they will also attack the species of most of the other Orders. Not unfrequently they deposit their eggs in various kinds of galls, formed by the agency of the preceding families ; and their progeny, when hatched, attack and subsist on the larvos inclosed within : and there are some species, whose larvae are parasitic upon those of other para- CHRYSIDID.E.— PRJEDONES. *1G5 sitic insects. Lastly, the CHRYSIDIDJE, or Ruby-tailed Flies, constitute a small group, distinguished by having the abdomen composed of only from three to five segments, — the remainder being formed into a tubular apparatus, capable of being drawn together, or extended like a telescope, and having a minute sting or ovipositor at its extremity. These insects, although but of small or moderate size, are amongst the most splendid of our native species ; being adorned with brilliant metallic tints, — usually blue and green on the head and thorax, and a fiery copper-colour or ruby on the abdomen ; hence they have been termed the humming-birds amongst insects. They may be observed during the hottest sunshine, flying and running with great vivacity over walls, palings, sand-banks, and occasionally upon flowers (especially those of the Umbelliferse) and leaves. The females do not insert their eggs in the bodies of other insects or their larvae, but take an opportunity of depositing them in the nests of the different Wild-Bees and other Hymenoptera, during the period when the latter are provisioning their nests for the support of their own progeny ; which is thus starved by the intruder, whose voracity is such as to require the whole supply of food that had been prepared for the legitimate occupiers of the nest. In this habit these insects closely resemble the Cuckoo (§ 351). In many points of structure, the Chrysididae bear a strong resemblance to the Aculeate Hymenoptera ; and they may be considered as intermediate between the two great divisions of the Order. 758. Section III. ACULEATA PRJEDONES. The Hymenoptera of the Aculeate division, like those of the second section of the Terebrantia, have the abdomen connected with the thorax by means of a peduncle or foot-stalk, which is often (as in the Wasp) extremely slender. — The Predaceous subdivision of this group contains several families ; of which the most important only will be noticed in detail. 759. The CRABRONID^K, LARRID^E, BEMBECIDJE, SPHEGID^E, SCOLIID^E, and ^IUTIL' ID^E, may all be considered under one general description ; they form a group, which may be termed, from their peculiar habits, that of Fossores, or Diggers ; and 166* FOSSORIAL PR^DONES. — FORMICID^, OK ANTS. they are commonly known as Sand and Wood Wasps. They are solitary in their mode of life, and consequently no neuters exist among them. In general the females excavate cells in the ground, or in posts, timbers, &c. ; in which they deposit — together with their eggs — various larvae or perfect insects, and (in some species) even spiders, which are destined for the sup- port of their progeny when hatched. Occasionally the insects composing this store are first stung to death ; but sometimes they are only slightly stung, and are finally killed by the larvae when they come forth, from their eggs, — being in this manner rendered powerless, whilst their bodies are prevented from decomposing. The perfect insects are generally very active, and fond of the nectar of flowers, especially those of the Umbelli- ferous tribe. They delight in the hottest sunshine, flying and running over sand-banks exposed to the mid-day sun, and keeping their wings in constant agitation ; some of the tropical species are among the largest of the order, and their sting is very severe. The Sand-burrowers excavate their nests, by means of powerful brushes, with which their legs are furnished ; whilst the Wood-burrowers use for this purpose their strong broad mandibles, which are 'provided with tooth-like projections. 760. The next family, that of FORMICID^:, is composed of the well-known and singularly interesting tribes of Ants (the White Ants, improperly so called, belonging however to the preceding order) ; which are distinguished from all the Hymen- optera previously described, by their habit of residing under- ground in numerous societies, and by the existence of neuters among them, by which class the labours of the community are chiefly performed. The males and females, which constitute but a small proportion of each community, are alone furnished with wings ; the former are the smallest. The neuters are somewhat smaller than the males, and for the most part resemble the females in conformation ; but the thorax is smaller, not having to give attachment to wings. The nests of Ants are differently constructed in the different species, but all are very curiously and regularly arranged ; some account of them will be given hereafter. The males and females leave the FORMICIDJE VESPID.E, OR WASPS. *167 nest as soon as they have acquired their wings ; and go forth together into the air. The males soon die, without re- entering their former abode. Of the females some return, and deposit their eggs in the original nest ; whilst others go to a distance, and become the foundresses of new colonies : they, too, lose their wings at this period, sometimes stripping them off with their own feet, in other instances being deprived of them by the neuters. — These last not only construct the nest, but most carefully tend the young grubs ; supplying them with food, moving them on fine days to the outer surface of the nest to give them heat, and carrying them back again at the approach of night or bad weather, and defending them when attacked by enemies. In most cases the species consist only of three kinds of individuals, males, females, and neuters ; but in a good many species, some of the latter are larger and rather dif- ferently formed from the rest, and appear to be the soldiers of the community ; — not only defending their own nests against attacks, but actually making war upon the nests of other species of Ants (as will be hereafter detailed), and keeping their cap- tives in slavery. Ants are well known to be extremely fond of saccharine matters ; and they seem greatly to relish the fluid which exudes from the bodies of Aphides and Coccida3 (§ 785, 786). Some species even collect Aphides into flocks, and keep them, as it were, in pastures ; which they connect with their nests by means of galleries, built along the stems and branches of trees ; and they protect the eggs of these insects in their own nests, especially in bad seasons. 761. The family of VESPID^E, or Wasps, is distinguished from the other Hymenoptera, by the wings being folded, when at rest, throughout their entire length. In general these insects are social ; the communities, however, being small. In such cases, there are neuters, or individuals of neither sex ; but these are not destitute of wings. There are also some solitary Wasps (whose habits resemble those of the Fossores, whilst their general structure is more conformable to that of the Social Wasps), among which no neuters exist. — The best-known of the Social Wasps, such as the Common Wasp of this country, 163* WASPS' NESTS. — MELLIFERA. FIG. 487.— NEST OF POI.ISTES. construct their nests with bits of wood, bark, &c., which they separate with their jaws and reduce to a pulp ; and this pulp, when ex- panded and dried, forms a paper-like substance. With this are built layers of hexagonal cells, one row being joined to the under side of another. The top row is attached, in some species, merely to the under sitfe of a branch, or to the roof of a slight hollow, by which it may be in some degree protected ; but in other species, the whole comb is enveloped in a covering, formed by several layers of the same paper-like sub- stance with one or more apertures (Fig. 488 ; and ANIM. PHTSIOL. Fig. 267). Wasps feed in their perfect state upon iusects, meat, fruit, &c. ; and nourish their young with the juices of those substances. A Brazilian species stores up an abundant provision of honey. — The nests of the Solitary Wasps are formed of earth ; they are sometimes concealed in holes of walls, in the earth, or old wood ; and some- times they are fixed to plants. The parents 3tore them with insects FIG.488.-NESTOFVESPAHOLSATICA. or caterpillars, which they have previously wounded with their stings. These nests contain a succession of cells, in each of which a single egg is deposited. 762. Section IV. The Hymenoptera belonging to the Mel- liferous, or honey-collecting, division of the Aculeata, are known by the peculiar conformation of the hind feet ; of which the first joint is compressed and extended into the form of a square plate, and provided on the inside with brush-like tufts ; these ANDRENID2E. — AFIDJE. *169 organs are employed for the purpose of collecting and carrying the pollen of flowers, which is destined for the nourishment of the young. All the insects of this tribe are commonly known by the name of Bees ; but the tribe, like that of Wasps, contains two different groups, — in one of which the species are all solitary, and there are only two kinds of individuals — males and females — in each ; whilst the others often live in societies of greater or less extent, but are chiefly distinguished from the former by certain peculiarities in the structure of the mouth. 763. In the Bees which constitute the family ANDRENID^E, the tongue is short, and blunt at the extremity, and the mentum or chin is elongated. They are always solitary in their habits ; the females form burrows in the ground, usually in sandy places, and provision these with masses of pollen and honey, in the midst of which they deposit their eggs. Each nest contains several such masses, each provided with an egg, and separated from its neighbours by small partitions of earth. The perfect Bees usually make their appearance in the spring. 764. The APID.E, or True Bees, are distinguished from the preceding by the great length of the tongue-, which exhibits the structure described in § 672. Their habits are very various and exceedingly interesting, their nests being constructed of the most different materials, and often displaying great ingenuity. Many of them burrow in the ground in the same way as the Bees of the preceding family ; others, known as Mason Bees, build a small edifice, consisting of several cells, with grains of sand or gravel, which they fasten together with a viscid saliva ; the Carpenter Bees (Fig. 490) form their cells in dead wood, which they excavate with their powerful jaws ; whilst the Up- holsterer Bees construct their nests with pieces of leaves, which they cut into the requisite form with surprising dexterity. The purpose of these operations is, in all instances, to form a series of cells, in each of which an egg is deposited, with a supply of UN- BEES ;— HUMBLE-BEES. pollen paste for the nutrition of the larvae. Some species, such as those of the genera Nomada, Melecta, and Ccelioxys, do not trouble themselves with the construction- of a nest, but introduce their eggs into the cells of other species of Bees. FIG. 490.— XYLOCOPA, OR CARPENTER BEE ; AND NEST. 765. Of the Social Bees, or APID^E, there are two principal groups ; the first consisting of the Humble- Bees or Wild-Bees ; and the second of the Hive-Bees. The Bombi, or Humble-Bees, of which there are many species in this coun- try, live in curious habitations, which are sometimes exca- vated at a consider- able depth in the ground, and some- times built upon its surface, beneath stones, &c. The so- cieties consist, in FIG. 491 -BOMBUS. some species, of about fifty or sixty indivi- duals ; in others of an many as 200 or 300. They contain three HUMBLE-BEES J HI VE-BEES. 1 7 1 kinds of individuals, — males, females, and neuters : of these the females are the largest, and the neuters the smallest. The females alone survive the winter ; and they employ the first fine days in spring to commence their nests, which they very quickly excavate, and supply with a mixture of honey and pollen for the nourishment of the first brood. This consists exclusively of workers or neuters ; which, after having undergone their transformations, assist in the labours of the nest, — both by the construction of new cells, the collection of food, and the rearing of the larvae. It is not until the autumn, that the males and females are produced. The former proceed from eggs laid by females, so much smaller than the rest, that they have been mistaken for workers. At the commencement of winter, all but the larger females die; these remain in a sort of chamber distinct from the rest, rendered warm by a carpeting of moss and grass ; but without, as it would appear, any supply of food. 766. It is in the Hive- Bees, that the arts of construction, and the union of individuals in societies, are exhibited in the most remarkable manner. These societies contain but a single perfect female, commonly termed the Queen, — several hundred males, which are known as Drones, — and about twenty thousand Workers or Neuters. It is by the latter that all the labours of the hive, — the construction of the combs, the collection of food, and the nourishment of the larvae, — are performed. The accompanying figures exhibit the relative sizes and aspects of these three kinds. The wax of which the comb is constructed, is secreted by the Fio.492— QUKKN BEK. FIG. 493.-'I)RONK BEE. FiQ.494.— NEUTER BEE. insects themselves, in little soales, which work out between the segments of the abdomen. These are taken up and kneaded by the jaws, and applied in the proper place. The cells are for the 172 HIVE-BEES. LEPIDOPTERA. reception of the eggs, of honey and of the pollen of flowers mixed with honey, into a paste known as bee-bread. This food is not deposited in the cells with the eggs ; but is supplied to the larvae by the workers, which tend them most assiduously. The honey is stored up for the support of the adults through the winter; a considerable proportion of the Neuters surviving, as well as the Queen, when the supply of food is sufficient. The Drones are killed at the end of the summer, by the stings of the workers, being themselves unprovided with any means of defence. The eggs are laid in the central part of each comb, which is the warmest situation ; those which are to produce Drones have cells constructed for them, which are rather larger than the rest ; and those from which Queens are to be reared, termed royal cells, are much larger and of different form. "When so many FIG.495.-ROYAL CELL. young Bees are Produced, that the hive is over-peopled, colonies are sent forth with young queens in search of another habitation. Further details on the economy of Bees have been elsewhere given (ANIM. PHYSIOL. §§ 712—716). ORDER VI.— LEPIDOPTERA. 767. This Order, characterised, as formerly stated, by the downy covering of the wings, contains some of the most beauti- ful forms of the whole class, as well as some of the largest. The number of species it comprehends is very considerable, although inferior to that of the Coleoptera, Hymenoptera, or Diptera ; it probably includes one-sixth of the whole class. All the insects of this Order are commonly ranked as Butterflies, Moths, and Sphinges or Hawk-moths; and whilst they are most readily distinguished from all others, there is so much general resemblance among themselves, that the difficulty of classifying GENERAL CHARACTERS OP LEPIDOPTERA. 173 Fio. 496. — FEATHER-SCALES OK THE GOAT-MOTH. them is often considerable. The possession of scales upon their wings is not alto- gether peculiar to them, for they are found upon the wiugs and bodies of other insects ; but it is only in those, that the \vings are covered with such complete layers of them. The scales are generally of somewhat oval form, terminating at one end in a kind of stalk, by which they are attached to the membrane of the wing ; and on this they are arranged in rows, overlapping each other like tiles on a roof. They may be easily rubbed off with the finger, and the bare membrane is left, which is then seen to correspond with that of the wings of other insects. The number of scales covering the wings of the Silkworm Moth, has been estimated at about 400,000 ; it is entirely tj these that the colours of the wings are due, which are frequently so gorgeous in this Order. In a few species, the wings are partially, or even almost entirely destitute of scales ; but the structure of the mouth, and their alliance in general characters with other species, leave no doubt that they belong to this Order. Of the peculiar adapta- tion of the mouth of the Insects composing this Order, for suction, mention has been already made (§ 674) ; and they are there- fore placed at the head of the Haustellate or Suctorial group, as the Coleoptera are at the head of the Mandibulate insects. Of their metamorphosis, also, an account has been given ; and it now only remains to describe some of the peculiarities of the larvae and pupae of this Order. 768. The first three segments of the body, in the Lepidopteroua larvae, have each a pair of simple, short, and jointed feet ; which are the rudiments of those of the perfect insect. Behind these are a variable number of temporary appendages, called pro-legs, which are thick, short, fleshy tubercles, armed at their extremity with a great number of minute hooks ; and furnished with powerful VOL. TI o 174 MOTION OF CATERPILLARS. muscles. There are usually five pairs of these — four of them succeeding the true legs, and another proceeding from the last segment of the body. Those possessing pro-legs on nearly every segment, crawl upon all the feet at once, after the manner of the Myriapoda; but those which have only a small number of pro-legs adopt a different method. They seize fast hold of the objects on which they are stationed, with the six true legs at the fore part of the body, and then elevate the intermediate segments into an arch, until they bring the pro-legs behind close to the others ; they then disengage the true feet, and retaining hold with the pro- legs, they thrust the body to its full length, and then re- PIO. 497.-CATKRPILLAR AND CHRYSALIS OF MAGPIK MOTH. COmmCnCC the Same manoeuvre, which they execute very quickly. They are called, from this circum- Fio. 498.— 1. CATERPILLAR OF SWALLOW-TAILED MOTH (Ourapteryx Sambucaria). 2. CATERPILLAR OF PRIVET HAWK-MOTH (Sphinx liyustri). stance, Loopers or Geometers. Many of them resemble small STRUCTURE AND HABITS OP CATERPILLARS. 175 pieces of stick in their forms and colours ; as well as in their mode of occasionally standing fixed to twigs, by their hind legs only, for a great length of time. Such an attitude requires a great amount of muscular force ; and we find that the muscular system of these Caterpillars is very complicated and highly developed (Fig. 499). It was stated by Lyonnet, who devoted many years to the study of the anatomy of the larva of the Goat-moth, that this contains 4041 distinct muscles. 769. The greater number of Caterpillars are vegetable- feeders, most of them confin- ing themselves to the leaves of plants; and the correspond- ence between the development of the leaves and flowers of plants on the one hand, with that of the Caterpillars and Butterflies which are respectively to feed upon them, cannot but strike every one as a beautiful example of creative foresight. But there are some Caterpillars, which are adapted to feed upon such flowers, as come forth early in the year ; and others attack seeds, roots, and even the woody portion of the stem. More- over, there are a few which live in this state upon animal matter, ,,* OW.-.BSTOK IORTK,X. such M w°o1' hides> leather> a"d fat. Many can digest a con- siderable variety of alimentary materials; whilst there are others that can only find support on some one kind, — the leaves of a particular species of plant for example. The habits of Caterpil- lars are extremely various. Some burrow into the substance of FIG. 499.— DORSAL MUSCLES OF THK ANTKRIOB SEGMENTS OF THE CATERPILLAR OP Cvssut. 176 CATERPILLAR AND IMAGO OF LEPIDOPTERA. leaves, in which they excavate galleries ; others envelope them- selves in the membrane of the leaf itself, which they roll together and attach by threads, — as seen in Fig. 500, representing the nest of the larva of Tortrix viridana (a small nocturnal moth) which is constructed by rolling the leaves of the Oak. Many construct cases or sheaths, either fixed or portable, by aggluti- nating several substances together, — as is done by the larva of of the common Clothes'-Moth ; and there are some that live in societies, dwelling together under a tent of silk, which they spin in common, and which serves to defend them from the incle- mency of the weather. 770. The imago, or perfect Insect, when it throws off its last envelope and comes forth into the air, of which it is hence- forth to be one of the gayest inhabitants, is not altogether perfect, although capable of very soon becoming so. The wings appear at first very slightly developed, and sometimes even hang loosely at the sides ; and it is not until the animal has injected their tracheae with air, — by taking several full inspirations and then forcing it into these passages, — that they become expanded so as to serve for flight. From that period the body is supported by them, during by far the largest pro- portion of their active state ; the legs being weak and used only VIG. 50!.— TORTOISE-SHELL BUTTERFLY JUST EMERGED KKOM THK CHRYSALIS. FIG. 502.— DANAIS PLEXIPPA. to rest upon, and one pair being sometimes undeveloped (Fig. 502). 77 1 . The Lepidopterous insects are divided into two sections ; DIURNAL LEPIDOPTERA, OR BUTTERFLIES. 177 which differ alike in their conformation and habits. These are, —I. The RHOPALOCERA, Diurnal Lepidoptera, or Butterflies, which may usually be distinguished by the vertical position of the wings during repose, and by their having the antennae slender, and terminated by a small club ; — II. The HETEROCERA, or Moths, in which the wings are horizontal in repose, and the posterior pair are furnished with a small bristle on their anterior margin, which usually fits into a small loop in the hinder margin of the anterior wings, and thus holds the wings connected during flight. This structure does not exist in the Butterflies. The antennae in the Moths are generally bristle-shaped, and frequently plu- mose. 772. Section I. RHOPALOCERA. — This section corresponds with the Linnasan genus Papilio ; which is now, however, very much subdivided. The Butterflies are distinguished from the other Lepi- doptera by the brilliancy of their colouring, and by the beauty of the under as well as the upper side of the wings. Their Caterpillars have usually sixteen feet ; and their Pupas are nearly always destitute of any silken envelope, and are attached by the tail. The Pupae of a great many species of this group are ornamented with golden spots ; from which circumstance the name Chrysalis is derived : this term ought, therefore, to be limited to the Pupa of the Butterflies ; but it is now in such ge- neral use, as applied to all Pupae, that it is undesirable so to re- strict it, and the term Aurelia (which means in Latin what Chrysalis does in Greek) is often employed by Entomologists to designate these Pupae. To the genus Vanessa, distinguished by the abrupt termination of the antennae in a short knob, belong several of the most beautiful of the British Butterflies ; — such FIG. 503.— ARGYKNIS PAPHI*.. 178 BUTTERFLIES. — CREPUSCULARJA, OR HAWK-MOTHS. as the Peacock (Fig. 504), the Painted Lady, the Camberwell Beauty, the Red Admiral, the Tortoise-shell, and others. The subdivisions of this Section bear so strong a resemblance to each FIG. 504.— PEACOCK BTPTTERIXY. other in structure and habits, that it is not requisite to describe them more minutely. 773. Section II. — The HETEROCERA, including the different kinds of Moths, present a much greater variety of structure than the Butterflies, and are in consequence divided into many fami- FIG. 605.— SPHINX OF THE VINE. lies. By many Entomologists they are primarily separated into two sections, of which the first, that of the CREPUSCULARIA, or Haiok-moths, corresponds with the Linnaean genus Sphinx; CHEPUSCULARIA ; SPHINGES, OK HAWK-MOTHS. 179 which derives its name from the peculiar attitudes, resembling that of the sculptured Sphinx of antiquity, into which the larva sometimes throws itself (Fig. 498, 2). The Moths have the an- tennas prismatic, and usually thickened towards the extremity, although the apex is slender and pointed. Although the Lepi- doptera arranged under this division are mostly twilight-fliers, this is not the case with all ; for there are some which come abroad in open day, and suck the juices of flowers with their long trunks, whilst the sun is brightly illumining their wings. These species are observed to be more brilliantly coloured than the rest ; the body and wings in most of the Sphinges having a dull, brownish- grey aspect, like that of many Owls, whose habits are similar. The larvae have always sixteen feet ; and the pupae are either inclosed in a cocoon, or bury themselves in the earth. The perfect insects make a loud humming noise in their flight. — One of the most remarkable of this group is the Acherontia atropos, Death's- Head Moth (Fig. 412), which is distinguished by the skull-like patch on the back of the thorax, as well as by the squeaking sound which it emits. In consequence of the peculiar aspect of the body, the sudden appearance of this insect in large numbers has been commonly regarded as ominous of evil. It is a great enemy to Bees ; entering their hives, devouring their honey, and alarming them so much, that they keep aloof from it instead of attacking it, although it has no means of defence. The Macroglossa Stella- tarum, or Humming-bird Hawk-Moth, commonly known under the name of " Bee-bird," is one of the most beautiful of the diur- nal species ; and is remarkable for the loudness of the sound which it produces, when feeding poised upon its wings. It might thus be almost regarded as the representative, in our own climes, of those feathered beauties after which it is named, that delight the eyes of the observer of Nature in tropical regions. 774. The group of NOCTUUNA, or True Moths, forming the second division of the Heterocerous Lepidoptera, is by far the most extensive of the Order, and includes the largest spe- cies. In their general aspect, Sphinges and Moths are some- what alike ; but they may be at once distinguished by the form of the antennae, which taper in the latter from base to point. 180 NOCTURNA, OR MOTHS. HEPIALIDJE ,' BOMBYCID^E. Many of them have no distinct trunk ; and in some species the females are almost, or altogether, without wings. Sometime-* the wings can be rolled round the body ; and in a few instance^ they fold longitudinally, like a fan. The greater part of thess Lepidoptera fly by night, and their colours are usually dull. Their Caterpillars vary as to the number of their legs, from ten to sixteen ; their pupae are of rounded form, and almost always spin a cocoon. The large number of species belonging to this section, and the general similarity of their form, make their classification a matter of some difficulty. They have been divided into ten families ; of which it will be sufficient here to notice the most important. 775. The first family, that of HEPIALTD.E, contains two interesting genera, Hepialus and Cossus. The Moths of the former are commonly termed Swifts, from the rapidity of their flight, which takes place during the twilight ; the sexes vary considerably in appearance and structure, — the male of one species, which frequents the Hop, being pure white, whilst the female is yellow, with darker markings. The male is commonly known as the Ghost-Moth, from his colour, and from his habit of hovering with a pendulum-like motion, over one spot (often in churchyards), where the female is concealed. The genus Cossus contains the Goat- Moth, one of the largest of British Lepidoptera; which has received its common name from the goat-like character of the strong scent emitted by the larva. This larva feeds upon the wood of willow-trees, which it per- forates in every direction, and thus so greatly weakens the trees, that they are often blown down with the first strong wind. It was this larva, which was so laboriously dissected by Lyonnet (§ 768) ; and his researches were continued upon the pupa and imago, so as to constitute the most elaborate and complete account of the anatomy of any Insect, that has been yet given to the world. 776. The family of BOMBYCID^E consists of Moths allied to that of the common Silk-worm. The pupae are inclosed in cocoons of pure silk, frequently of very firm texture ; and they are rarely subterranean. The prevailing hues of these Moths BOMBYCIDJE, OR SILK-WORM TRIBE. 181 are grey or fawn colour ; and many of the larger species have the wings ornamented with eye-like spots (Fig. 506). This FIG. 506.— EMPEROR MOTH. trihe contains the largest species of Lepidoptera. The Saturnia pavonia major, found in France, has been seen to attain the breadth of five inches across the wings; and the Saturnia pavonia minor, or Emperor Moth of this country (Fig. 506), attains the breadth of 3^ inches. Many of this genus are remarkable for the FIG. 507 — SATURNIA PROMKTHKA. contrivances they adopt for security in the Chrysalis state ; and among the most so is the Saturnia promethea (Fig. 507), an 182 MOTHS. — BOMBYCID.E. FIG. 508.— CATERPILLAR, LEAF-COCOON, AND CHRYSALIS OF THE PROMETHEUS MOTH American species, which, previously to spinning, draws together the sides of a leaf (within which it afterwards forms its cocoon), and fastens its stalk to the stem by a strong silken web (Fig. 508). The genus Bombyx is one of great in- terest and import- ance, as containing the Bombyx mori, whose larva fur- nishes all our silk. Of the numerous other species of the family, some much resemble a bundle of dead leaves, both in colour and form, when their wings are closed ; such is the Gastropacha quercifolia, or Oak-leaf Moth (Fig. 509). The Caterpillars of other species are re- markable for their curious habits. They live in societies on the leaves of the oak ; and spin, when young, a kind of silken tent, divided within into cells. They may be seen to issue from it in the evening in a procession, — one of them, which seems to act as a guide, advancing at the head, — two then following, — then three, — then four, — and so on, each rank containing one more than the preceding one. Hence they have been called processionary caterpillars. Each spins a separate cocoon ; but they are united in regular apposition, being laid side by side against each other. 777. The family NOCTUID^J contains a great proportion of FIG. 509.— GASTROPACHA QVER- ClFOLlA. NOCTUIDJE ; GEOMETRIC ; TORTRICID.E. 183 Pl«. 610.— ABRAXAS GKOSSULARIATA. the large sombre-coloured night-flying Lepidopterous insects ; it includes 400 British species, which bear a very strong re- semblance to each other.— The family GEOMETRID.E, so named from the peculiar mode of progression of its Caterpillars (§ 768), is nearly allied to the preceding ; \>ut the moths it includes are less exclusively nocturnal, and are more brightly coloured. To this •family belongs the com- mon Magpie Moth (Fig. 510), whose larva and pupa have been already represented (Fig. 497) ; also the Swallow-tailed Moth, and many other well-known species. — The TORTRICIDJE constitute a numerous group, composed of minute and usually dull-coloured Moths, whose larvae are ex- tremely destructive to vege- tation. One of these, known as the Codling Moth, is one of the most destructive ene- mies to the Apple crops of this country ; laying its eggs in ijie eyes of the newly-formed fruit, within which the larva feeds, its presence being only- indicated by the premature falling off of the fruit. — Another species does great damage to our apricot trees in the early spring, by tying the young shoots together with threads, so firmly that no. 511— TORTMX vms. their growth is stopped, and by devouring the young blossom-buds. Another species (Fig. 400) feeds upon the Oak, which in certain years it totally strips of its foliage : its numbers 184 TORTRIX.— CLOTHES'-MOTHS ; PLUMED MOTHS. being so great, that when the branches of that tree are sharply- beaten, a complete shower of these moths is dislodged. And another commits great havoc in our gardens, by eating the young leaves and buds of the roses ; the caterpillar feeding within the bud, from which, when disturbed, it lets itself down by a thread. One of the most destructive insects of this family is the Tortrix vitis (the Pyrale of French Entomologists) ; whose larvae com- mit extensive ravages in the Vineyards of some parts of France, where they occasionally appear in very large numbers, devouring and tying together the leaves, and preventing the development of the grapes, by surrounding them with the silken threads of which they make their cocoons (Fig. 511). 778. The family TINEID^E contains those little Moths, com- monly termed Clothes' -Moths, whose larvae are so injurious to woollen stuffs of every kind, as well as to furs, skins, feathers, and other objects of natural history, upon which their voracity is exercised. They use the same materials also for the construc- tion of their moveable cases or sheaths ; which they enlarge with the increasing size of their bodies, both by adding to their extremities, and by slitting them along and inserting a new piece, so as to increase their diameter. In these tubes they undergo their metamorphoses, after closing the orifice with silk.— The larvae of the genus Galleria infest Bee-hives, feeding upon honey, forming galleries in the honeycomb, and enveloping the bees in their silken webs, sometimes to such an extent as to destroy the community. The larvae of most of these moths, however, feed upon fresh vegetable matters, usually attacking the leaves, from which some of the species manufacture small portable cases, whilst others feed upon the pulp between the cuticles of the leaves, leaving the surface uninjured. These form curious little galleries in the substance of the leaves, from which they are denominated Leaf-miners. 779. The FISSIPENN.E, or Plumed Moths (Fig. 404), consti- tute a small group, distinguished from all other Lepidoptera by the singular division of the wing into branches or rays, of which each pair has from two to six ; these are most beautifully fringed at their edges, and much resemble the feathers of Birds. RHYNCHOTA ;— HOMOPTERA. 185 They are composed of the nerves alone, without any intervening membrane ; this last seeming to have been transformed into the fringe. The Plumed Moths are of small size ; some of them are diurnal and brightly-coloured ; others are twilight-fliers, and of a duller aspect. Some species have the power of folding up the wings like a fan ; so that, when closed, they present the appearance of a single broad ray. ORDER VII.— RHYNCHOTA. 780. The Insects of this Order, which correspond with the Hemiptera of Latreille, present many curious anomalies both in structure and habit. It is in the construction of the mouth that there is the greatest agreement ; this is adapted for suction, the lower lip being elongated, jointed, and channeled like a gutter, inclosing four bristle-like organs, which are the representatives of the mandibles and maxillae (§ 673). Their food consists of the juices of animals and plants, the majority deriving their nourishment 1'roin the latter source. — Their metamorphosis is incomplete. Their differences of organisation may be referred to two principal types, by which means the order is divided into two sub-orders : these are, — I., the HOMOPTERA, with the anterior wings of the same consistence (either membranous or leathery) throughout, and the mouth directed backwards, so that the ros- trum originates from the posterior part of the head ;— and II., the HETEROPTERA, in which the anterior wings are distinctly divided into two portions, the basal horny, and the apical mem- branous ; and the rostrum springs from the anterior margin of the head. 781. Sub-order I. HOMOPTERA. All the Insects of this group subsist on vegetable juices ; and some of them, from the amount of damage they commit, are very injurious to the culti- vator. Some of the females are furnished with an ovipositor, provided with several toothed saws ; and with this they make 186 CICADID^E, OR CICADAS. incisions into the leaves and stems of plants. This sub-order may be divided, like the Coleoptera, according to the number of joints in the tarsi. These sections are only three in number: in the first, TRIMERA, the tarsi are three-pointed. ; in the second, DIMERA, they are but two-jointed ; and in the third, MONOMERA, they have but one joint. 782. Section I. TRIMERA. The three-jointed division of the Homoptera includes three families, the CICADID^E, or Cicadas, the CERCOPID^, or Froth-hoppers, and the FULGORIDJE, or Lan- tern-flies.— The CICADID^E are the largest of the Order ; one species measuring between six and seven inches in the expanse of its wings. They are nearly all inhabitants of tropical or the warmer temperate regions ; only one small species having been found in this country. They have large wings, which are sometimes transparent and sometimes opaque, but are not very active in their habits ; being generally found upon trees or shrubs, whose juices they suck. The female makes a suc- cession of slits in the small twigs with her ovipositor, and deposits her eggs in these ; the young larvae soon quit their birth-place, however, and descend to the ground, where they increase in size and become pupae. It is a species of Cicada inhabiting a kind of Ash, which, by puncturing it, causes it to discharge the sweet, slightly purgative substance, that is known as Manna. — Of the peculiar sound-producing powers of the Cicadidae, an account has been elsewhere given (ANIM. PHYSIOL. § 679). The ancient Greeks used the pupae and perfect insects as articles of food. 783. The FULGORID^E bear a general resemblance to the Cicadidae, but are destitute of organs for producing sound, and FIG. 512.— CICADA. FULGORID^E, OR LANTERN-FLIES. — CERCOPID^E. 187 FIG. 513.— FULOOEA LATERNARIA. have the legs more adapted for leaping. Many of them are distinguished by a curious prolongation of the forehead, which sometimes equals the rest of the body in size. The shape of this projection varies extremely in the different species, which are numerous in many tropical regions. It is in it, that the luminous property of the Lantern-fly (Fig. 513) v said to exist ; but th< luminosity of this in sect, — of which one spe cies is a native of Guiana, and another of China, — is doubted by many na- turalists, the evidence in regard to it not being sufficient. If it really exists, it is only at particular seasons. The Lantern-fly of Guiana seems to be an exception to the general rule, with respect to the absence of sound-producing powers in this family ; for it is said to produce, from sun-set to sun-rise, a loud sound, which has been compared with that of a razor-grinder at work. 784. The family CERCOPID^E consists of insects of small size ; many of which are remarkable for the grotesqueness of the forms they assume. Several species are inhabitants of this country, and are known under the name of Frog-hoppers, from their leap- ing powers ; or of Froth-hoppers, from their peculiar frothy secretion ; or of Cuckoo-spits, from the supposed origin of this fluid. The most singular forms, however, are confined to the tropics ; and exam- ples of them are present- ed in the accompanying figures of two Brazilian species, whose curious Fio.514.-a,Bocydiumglobulare;6,B.cruciatum. appendages resulfc from an extraordinary development of the first segment of the thorax. The insects of this family are often beautifully varied in their colours ; they are constantly found upon plants, upon the juices 188 FROTH-HOPPERS.— APHID JE, OE PLANT-LICE. of which they subsist in all their stages ; and some of them are employed by certain species of Ants, for the same purposes as the Aphides (§§ 760 and 785). The Aphrophora spumaria is one of the best known British species ; its larva and pupa, resembling the perfect insect in almost every respect save the absence of wings, are no. 515.-APHROPHORA spTJMARiA : «, imago , found beneath a frothy b, frothy secretion j c, pupa. exudation, — especially upon willow-trees ; and the exudation is sometimes so abund- ant, from the large number of these animals, that persons walking beneath are wetted by the continual dropping of the fluid. A species nearly allied to this, inhabiting Madagascar, discharges a clear instead of a frothy fluid ; and this in such quantities, that it falls to the ground in the middle of the day, when the heat is the greatest, in a continual shower. 785. Section II. DIMERA. This section entirely consists of minute insects ; of which the most remarkable family is that of APHID^E, or Plant-Lice. These live in great numbers upon the surface of plants of almost every description, and suck the juices, by means of their proboscis, from the young shoots, leaves, stems, and even roots. They greatly weaken its vigour, and often distort young shoots and leaves ; some species cause little gall-like excrescences, by the irritation they produce. From two horn-like processes at the posterior part of their bodies, a saccharine secretion exudes, of which Ants are very fond (§ 760) ; and it is either this fluid dropped on the adjacent leaves, or the extravasated sap flowing from the wounds made by the insects, which is known under the name of honey-dew. In many of the species of this family, a large proportion of the individuals never acquire wings ; in which case the pupa is not to be distinguish- ed from the larva or imago ; whilst at certain parts of the year, other individuals of the same species, and of both sexes, acquire wings. The Aphides which are seen in the spring and summer are sexless individuals, which produce living young by a process APHIDES, OR PLANT-LICE.— COCCID.E. 189 of budding in their interior. In the autumn males and females are produced in the same way, and the latter lay eggs, which survive the winter and give birth to viviparous individuals in the ensuing spring. This is an example of what is called the " Al- ternation of Generations," the only one met with amongst Insects, although it frequently occurs amongst the lower classes of the animal kingdom. The rapidity of production of the viviparous individuals is enormous ; nine generations having been produced within three months, and each generation averaging 100 indivi- duals. Hence it may be calculated that, from a single Aphis, 10,000 million millions may be generated in that short period. It is not surprising, then, that an immense amount of damage should be done by them, notwithstanding their very small size. Many of the blights so injurious to the gardener and the agricul- turist, consist really of Aphides ; although, from the minuteness of the insects themselves, they frequently escape observation. The Aphis Rosce, or Rose Louse, is one of those best known to the gardener ; whilst the one most destruc- tive to the property of the cultivator on a larger scale is the Aphis Humuli, or Hop Fly. Of the extent of its influence on the FIG. 516,-ApHis BOSJE. production of that vegetable, some idea may be formed from the fact, that the duty paid to the English government on its growth, has varied from 468,000/. to 15,400/. in different years, almost entirely from the absence of this insect in the former case, and its presence in the latter ; and the differ- ence in the actual value of the crop is, of course, far greater. 786. Section III. MONOMERA. The third section contains but one family, that of Coccus, sometimes called Scale Insects. These, although ordinarily of very small size, are amongst the most injurious to vegetation of the whole tribe. Like the last, they are remarkable for their powers of propagation ; and when they once gain possession of a plant or young tree, its death is almost certain, — the minute size of the larvae rendering it almost impossible to exterminate them. They furnish, however, some very important products. The bodies of many species are deeply coloured through their whole substance, and yield dyes of great value ; the richness of which seems to depend upon the nature VOL. II. P 190 COCCIDJE, OR SCALE INSECTS; — COCHINEAL. of the plant on which they feed. The Coccus of the ancients was a native of the Levant ; but that which furnishes the Cochineal so highly valued at the present time, was originally confined to Mexico, where it feeds on the plants of the Cactus tribe ; it has been introduced, however, along with its proper food, into Spain and Algiers, as well as into the hot-houses of this country. Immense quantities of Cochineal are annually brought to Europe; in the year 1850 the quantity imported into Britain alone was 2,514,512 lbs.,each pound containing about 70,000 insects. The Lac of the East Indies, which is extensively employed in the composition of varnishes, the making of sealing- wax, &c., is the product of another species of Coccus. The species which inhabit our own country, are important rather on account of the damage they commit, than the benefit they afford to man. The bark of many of our trees often appears warty, by reason of a great number of small oval or rounded bodies, like a shield or scale, which are fixed to them, and in which no external traces of the insect are to be observed. These, however, are Iarva3 belonging to the tribe in question. Some of them are females ; others young males, which are similar to them in form. At a subsequent period, they all undergo singular transforma- tions. The males fix themselves to the plant, and pass into the pupa state, in which they remain completely at rest ; and at last emerge as winged insects, — coming out of their cocoons backwards, with the wings extended flatly over their heads. The females, on the other hand, remain attached to the plant, and increase in size, in consequence of the development of a large number of eggs in their interior ; but they undergo scarcely any other change. The eggs are deposited between the lower side of the body, and the surface to which it is attached ; the latter having been previously covered with a sort of cottony secretion. The parent then dies, and her body dries up and becomes a solid cocoon, which covers the eggs. Here the eggs are hatched ; and the young larvae, which are at first active in their habits, quit their envelope, and ascend to the extremities of the branches ; there they affix themselves by their sucking-beak, gradually in- crease in size, and lose their activity. In this condition they HETEROPTERA ;— LAND-BUGS. 191 pass the whole winter ; and it is not until the succeeding spring, that the characters of the sexes, which are henceforth to be so distinct, begin to show themselves. 787. Sub-order II. HETEROPTERA. By far the greater number of the Insects of this group feed, like the preceding, upon the juices of plants ; but some of them prey upon other and weaker Insects ; and a few species (of which the numbers, however, sometimes multiply to a great ex- tent) suck the juices of larger ani- mals. The majority of the species are found in tropical climates ; and the species that inhabit those re- no. 517.-PENTATOMA. gions, Sire mostly ornamented with a great variety of beautiful colours and markings, which often vie with those of the most splendid >f the Beetle tribes. Many species, however, are of aquatic labits ; and these are all of an obscure or black colour. Nearly ill the terrestrial species have the power of emitting, when they are suddenly alarmed or touched, a strong odour ; which is of a pleasing character in some species, but which in others (as the common Bed-bug) is very disgusting. Many of them seem to inject a poisonous fluid into the wound which they make for the purpose of suction. In some species, the wings are alto- gether undeveloped ; or the lower pair is wanting. They may be divided into two sections, distinguished by their resi- dence, and by the modifications of their structure in accordance with it ; — the GEOCORIS^, or Land-Bugs ; — and the HYDRO- CORISJE, or Water-Bugs. 788. Section I. GEOCORIS^E. This section contains a large number of families ; nearly all of which, however, bear a strong general resemblance to that which includes the common Bugs, — .the CiMiciDvE. Some of the tropical species attain considerable size, and they are much dreaded by the inhabitants of the regions they infest. Most of the Geocorisaa, however, are vegetable- feeders ; and it is among these that the most brilliant colours 192 LAND-BUGS ;— HYDROMETEID.E. are exhibited. It will be unnecessary to describe in detail the numerous groups into which this section is divided, but a few of the most important of them may be briefly alluded to. The largest species belong to the tribes of the SCUTATA and COREODEA, both of which include none but vegetable-feeders. — The SCUTATA are distinguished by the great length of the scutellum, which always reaches the base of the membranous part of the elytra (Figs. 517, 518), and in some cases covers the whole back of the insect. The antennae in this group are usually composed of five joints. — Many of the LYG^EODEA are distinguished by their beautiful scarlet colour; whilst the BICELLULI, including the majority of the European species, are characterized by having the veins of the membrane of the elytra arranged so as to form two small cells at the base. The preceding Insects, with but few exceptions, have the rostrum composed of four joints, and their food consists for the most part of the juices of plants ; the remainder of the Geocorisse have a stout rostrum consisting of three joints, FIG. 518.— HALTS. PIG. 519.— CIMEX LECTULAEITJS. and their habits are usually predaceous. — To this group belongs the family CIMICID^E, which includes the common Bed-bug (Fig. 519), and the REDUVIIDJE, containing the largest of the species which derive their nourishment from animal fluids. The wounds inflicted by many of the latter are attended by a very severe pain. — There is a curious group of very long-legged insects, which, though placed in this section, leads to the next ; this is the family HYDROMETRHXE, some species of which may be met HYDROCORIS.E, Oil WATER-BUGS. 193 FIG. 520.— NOTO- NECTA. with on almost every pond or stream, skimming along the sur- face, and turning rapidly about, with the greatest ease and velocity. The form of the body strongly resembles that of a London wherry ; the hind feet conjointly act as a rudder ; and the motion is given by the two middle feet, which do not, how- ever, dip into the water, but merely brush along its surface. The body is clothed on the under side with a fine coating of hairs, forming a sort of plush ; which is evidently serviceable in preventing it from coming in contact with the water. 789. Section II. Of the HYDROCORIS^I, or true Water- Bugs, there are two families only. The NOTO- NECTID.2E, or Boat-flies, live almost entirely in the water, where they feed upon other aquatic insects ; these they seize by means of their fore- legs. The legs of the hinder pair have a fringe of bristles along their edge ; by which the sur- face with which they strike the water in swim- ming is greatly increased. Their general form is extremely well adapted for rapid progression ;n water ; and it is from the peculiar aspect and movement of the body, that they have received the name of boat-flies or water-boatmen. The insects of this family swim on their backs ; and the arrangement of all their organs has reference to this posi- tion. When stationary at the surface of the water, as is much their custom in calm hot weather, they very quickly obtain intelli- gence of the approach of danger, by means of their eyes, which are so placed that they are able to see both above and below the surface ; and then, by a single stroke of their paddles, which are commonly stretched out at full length, they descend out of sight. Their motions are very quick in the element they are chiefly formed to inhabit ; whilst on land ;y are scarcely able to walk. They can fly well ; but they farely exercise this power. The larva and pupa only differ PIG. 621.— NEPA CINEREA. 194 HYDROCORI9.E, OR WATER-BUGS. from the imago in their smaller size, and in the deficiency of wings. When they descend into the water, the Notonectidae carry down a supply of air for respiration, in a hollow which exists beneath the wings, when these are folded together. — The NEPID^E, or Water- Scorpions, receive their name from the scor- pion-like form of their fore-legs, which are efficient instruments for seizing their prey. They are in most respects similar in structure and habits to the insects of the preceding family ; but their motions are much slower, their legs not being so advantage- ously formed for swimming. The species represented in the ac- companying figure is a very common inhabitant of our ponds. 195 ORDER VIIL— DIPTERA. 790. THE tico-winged insects constitute one of the most extensive Orders in the whole Class, not only in regard to the number of distinct species, but also from the occasional excessive multiplication of individuals of the same species. Many of them, also, have been constant attendants upon Man in all ages. They do not attract attention, however, from their size, for there are few that exceed an inch in length ; nor is it on account of their beauty, for the majority of them are of dull colours ; their forms, too, are rarely elegant ; and of the habits and metamorphoses of a large proportion of them, very little is known. They owe the notice they have attracted, chiefly to the habits of certain species; which affect Man and the Domestic Animals, in various ways, both in their perfect and early states. However annoying these may be, it must not be forgotten, that other Diptera are of extreme service, in cleansing the surface of the earth of vege- table and animal impurities ; and the carcass that is full of maggots would be much more prejudicial in its decomposition, than it is when principally eaten up by these voracious creatures. The mouth in the insects of this order is formed for suction, as already described (§ 674) ; but there are considerable varieties in the mode in which this is accomplished. Behind the wings are found a pair of moveable slender bodies, termed halteres, or balancers ;- these are probably the representatives of the second pair of wings. They are kept in continual motion', and are usually present even when the true wings are not developed. The Diptera all undergo a complete metamorphosis, the Larvae being generally cylindrical footless grubs, with no representatives of legs, except in a few species. In many cases, at the time of the transformation into the Pupa state, the skin of the larva is not thrown off, but hardens and contracts} so as to form a kind of cocoon. Within this, the body of I9G METAMORPHOSIS AND SUBDIVISION" OF DIPTERA. FIG. 522.— LARVA, PUPA, AND IMAGO OF STRATIOMVS CHAMJELEON. the larva is found, at first apparently but little altered, except that it has become de- tached from the skin, to the inside of which the organs peculiar to the larva, such as the parts of the mouth, remain adherent. Shortly after- wards, the in closed being assumes the form of a soft and gelatinous mass, in which none of the parts of the future insect are yet visible ; some days afterwards, how- ever, these organs become distinct, and the insect has then assumed the real state of pupa, though without having yet thrown off its larva skin. When ready to escape, it scales off the anterior end of its case, like a cap. Many larvae, however, do throw off their skins when assuming the perfect state, and some form a regular co- coon. The duration of life in the perfect state is usually very short. 791. In subdividing this Order, we first separate from it a small but remarkable group, which forms the transition to the more aberrant orders of the class, especially the Aphaniptera. Some of them are entirely destitute of wings ; and yet in their general structure they correspond with the Diptera. They are distinguished from all other insects by their curious mode of reproduction. Not only are the eggs hatched within the body of the parent, but the Larvae are retained there until they have been transformed into Pupse, in which state they come forth to the world. Hence this section has received the name of PUPI- PARA. It contains two families, all the species of which are parasitic. The HIPPOBOSCID^E, sometimes called Forest Flies, are of small size, covered with bristles, and frequently destitute of wings. They are known by the French under the name of Spider-Flies. They reside upon quadrupeds and birds, running with great agility, and often sideways, burying themselves SUBDIVISIONS OF DIPTERA.— CULICTDJE, OR GNATS. 197 amongst the hair or feathers. That which is parasitic on Sheep is known as the Tick. One minute species infests the Hive-Bee ; and this is remarkable, not only for being destitute of wings, but of eyes also. In the other family, that of NYCTERIBIID^:, the general form still more nearly approaches that of Spiders. The group contains but a small number of species, all of which are parasitic upon Bats, and are termed Bat-Lice. 792. The remaining Diptera, constituting by far the larger proportion of the class, may be subdivided into four sections. In the first, NEMOCERA, the antennae are composed of more than six joints : whilst in all the remainder, the antennae are short, not having more than three apparent joints. In the second, NOTA- CANTHA, the last division of the antennae is really composed of two or more ; the proboscis does not project much from the mouth, and is furnished with only two lancets. In the third, TANYSTOMA, the antennas have only three joints, the last usually terminated by a seta or bristle. And in the fourth, ATHERICERA, the antennae are only two- or three -jointed, and the proboscis is capable of being withdrawn into the mouth. 793. Section I. NEMOCERA. To this division belong the two families of CULICID^E and TIPULID^E ; the former known as the Flo. 623.— CULEX PIPIENS, female, natural size and magnified, with head of male, and the larva. Gnat tribe, the latter as the Harry Long -legs. Both are remarkable for their beautifully-tufted antennae ; but the former are distinguished by the length of the proboscis. Gnats are well known to abound chiefly in damp situations; the reason being, that their larvae are inhabitants of the water. In this state they are very active, swimming with great agility, and often descending ; but coming to the surface to breathe, whicii 198 CULICID^E, OR GNAT-TRIBE. TIPDLID^E. they do head downwards, the respiratory orifice being at the end of a very prolonged spiracle arising from the end of the abdomen. When the final transformation occurs, the skin of the pupa, which is being cast off, serves as a kind of raft, which prevents the perfect insect from being immersed in water, and thus wetting Hs wings. The Mosquitoes, which infest many countries, espe- cially in warm latitudes, or during the brief but hot summers of some colder ones, differ but little from the common Gnats. They sometimes appear in such swarms, especially in marshy districts, that they can be only kept off by fire. Their rapid multiplica- tion is easily understood, when it is known that their whole series of metamorphoses only occupies three or four weeks in summer, so that there may be several generations produced in the course of one season ; and that each female lays several hundred eggs. — The TIPULIDJE also have feathered antennae, but their proboscis is very short. Some of them very strongly resemble Gnats, both in the larva and perfect states ; such are the Midges, of which one species is repre- sented in Fig. 524. In another group, there is a strong resemblance to the Cynipidee, or Gall-flies ; both in their minute size, veinless wings, and mode of life. Their larvEe are terrestrial, and are very commonly developed within a sort of gall, produced by the punc- ture made by the parent in the tissues of plants, when depositing its eggs. Some species make their puncture in the young sprigs, others in the leaves, and others in the flowers ; and there are several which are extremely injurious both to the Gardener and the Agriculturist. Thus the Wheat crops of this country are often seriously injured by the Cecidomyia Tritici ; the eggs of which are deposited by the female in the centre of the flower, where the larvae are hatched ; and it is probably by devouring the pollen, that they are most injurious to the plant. Another species, FIG. 524.— CHIRONOMUS, with its Pupa and Larva, magnified. TIPULID.E. NOTACANTHA. TANYSTOMA. 199 C. destructor, is known in America under the name of the Hessian Fly ; this attacks the lower part of the stem of the wheat. The FIG. 525.— CKCIDOMYIA DESTRUCTOR, and C. TRITICI, with the Larvae of the latter feeding in wheat flowers, magnified. proper Tipulce, or Harry Long-legs, are the largest species of the family. Their Iarva3 generally live in the earth, in the rotten parts of trees, &c., and many of them do great mischief by feed- ing upon the roots of grass and corn. 794. Section II. NOTACANTHA. The second Section of the Diptera contains three families, STRATUOMID^E, BERID^E, and CCENOMYID^E, which do not attract much attention, although some of the species contained in them are very abundant. They are mostly small but gaily-coloured insects ; and are most nume- rous in moist situations, in which the larvae are generally pro- duced. Some of the larvae, as that of Stratiomys Chamcsleon (Fig. 522), are completely aquatic; and respire, like the larvae of the Gnats, by extending their tails to the surface, the spiracle or breathing-pore being in that situation. They mostly feed upon vegetable, rather than upon animal, juices. 795. Section III. TANYSTOMA. The insects composing the third section have usually a more perfect mouth than those of the other divisions ; and they are also remarkable for the structure of the head of the larvas, which possess two claw-like appen- dages, by which they attach themselves to the substances that afford them support. Many of the perfect insects are eminently carnivorous or insectivorous ; as are also some of the larvae. There is a genuine metamorphosis in this group ; the larva-skin being cast off at the entrance of the animals into the pupa-state. In this state they much resemble the perfect insect; the limbs being inclosed in distinct sheaths, and folded on the breast. 2UU TABANID^E, OR GAD-FLIES. — BOMBYLIIDJE. The perfect Insect escapes from the pupa-skin by means of a slit along the back. To this group belongs the family TABANID^E, or Gad-fly tribe; which com- prises some of the largest Di- pterous insects, and which is pre-eminently distinguished for the tormenting powers which different species possess. They pierce the skins and suck the blood of various Quadrupeds, FIG. 526 — TABANUS BOVINUS. . both wild and domesticated ; and do not spare Man himself. They chiefly abound in woods and pastures ; and the buzzing noise which they make, has obtained for them the designation of " the breeze." The insect of which Bruce has spoken, in his Travels in Africa, under the name of Zimb, is probably a species of this family. He describes it as attacking cattle in so dreadful a manner, that, unless imme- diately driven to thousands, they forsake their food, and run wildly about the plains, dreading even its very sound, until they die, worn out with fatigue, fright, and hunger. The Camel, and even the thick-skinned Elephant and Rhinoceros, are said to be subject to this enemy. 796. The family BOMBYLIID^ are distinguished by their very long proboscis, with which they suck the nectar from flowers. They fly with great rapidity, and hover over flowers without settling ; making at the same time a loud buzzing noise with their wings. Some of them have a remarkably Bee-like form. The family ANTHRACIDJE, which is nearly related to the preceding, is chiefly composed of exotic species, which are generally large or of moderate size, often covered with hair, and beautifully coloured. They fly in the sunshine with great agility ; and subsist, like ATHERICERA; — SYRPHID^E, OR WASP-FLIES. 201 the preceding, upon the juices of flowers. In general the pro- boscis is comparatively short ; but in a few instances, as in the Nemestrina longirostris, it is of extraordinary length (Fig. 421). This section also contains several other families of less interest and importance ; among them we may mention the ASILID^:, which live by rapine, seizing Flies, Tipulse, Humble-Bees, and even Wasps, and sucking their juices. 797. Section IY. ATHERICERA. The Dipterous insects of the fourth tribe are principally vegetable-feeders in their perfect state, only a few being carnivorous or insectivorous ; but their larvae are generally extremely voracious, and will devour almost any kind of soft animal matter. This section includes the Flies strictly so called, the Bot-flies, and many other tribes. — The first family, that of SYRPHID^E, bears an extremely close resemblance to the Humble-Bees and Wasps, in the nests of which some species among them deposit their eggs ; this resemblance is evi- dent in the accompany- ing figure, which repre- sents the Eristalis, or Drone-fly (A), and the Anthophora retttsa, or Spring Wild-Bee (B), two insects which differ entirely in their habits, FIG. 528.— DRONK-FLY AND SPRING WILD-BKB. — the former being the very personification of luxurious idleness, doing nothing but sip the nectar from the brightest flowers and bask in the sunshine on the leaves, — whilst the latter toils all day long, either in the construction of the nest, or in provisioning it with pollen paste. The larvae of the genus Volucella, of which the perfect insects resemble the preceding, live as parasites in the nests of Bees and Wasps. Some species restrain, in a similar manner, the exces- sive multiplication of the Aphides. The perfect insects feed almost solely upon the juices of flowers, preferring those of the Composite ; and they delight to hover immoveably over certain spots, to which they will return, if disturbed, a considerable number of times. Above a hundred species inhabit Britain. In 202 MUSCID2E, OR FLY-TRIBE ;— MAGGOTS. a few of them the larvae are aquatic, and the posterior part of the body is prolonged into a respiratory tube, whence they have received the name of " rat- tailed " larvae. This is the case with the Eristalis above represented, and with several allied species. 798. The form and habits of the family MUSCIDJE, or Fly tribe, are generally known. The family is an extremely nume- rous one, above 1700 species having been recorded as existing in Europe, of which about half are natives of this country ; and there are probably at least as many more, which have not been described. The strong general resemblance which exists among all the species, together with their small size, makes it difficult to discriminate them readily. The larvse of these insects, com- monly known as maggots^ are soft, worm-like, footless grubs, possessing on the head a couple of retractile hooks, by which they can cling to the substances on which they feed. They devour various substances, both animal and vegetable, living, recently dead, or far advanced in putrefaction. The eggs are deposited by the female (as in other instances) in the neighbour- hood, or in the very substance, of the food which is adapted for the support of the larva, however little this may be to its own liking. Some of these larvse are remarkable for their leaping powers, — whence they are commonly termed " hoppers." This is especially the case with the larva of the Piopkila casei, or Cheese-hopper ; whose mode of springing into the air is very curious. FIG. 529.-1. The CHEESE-HOPPER preparing to spring.- When preparing to 2. Natural size of the Larva. — 3, 4. The Fly to which ], ap it first raises it is transformed : natural size and magnified. itself on its tail ; in which position it is enabled to balance itself, by means of some prominent tubercles on the last segment of the body. It then bends itself into a circle ; and having brought the head towards the tail, it stretches out the two hooks ,of the mouth, fixing them into two cavities at the other extremity of the body. MUSCIDJS, OR FLY-TRIBE. MAGGOTS. 203 It then contracts the body from a circular to an oblong figure ; the contraction extending in a manner to every part of the body. It now suddenly lets go its hold, and straightens the body, with such violence, that the noise produced by its hooks is very perceptible. The height of the leap is often from twenty to thirty times the length of the body ; exhibiting an energy of motion, which is particularly remarkable in the soft Larva of an Insect. A Viper, if endowed with similar powers, would throw itself nearly a hundred feet from the ground. The learned Swammerdam, who devoted much attention to the anatomy and habits of this creature, observes — " Now let the sharpest geniuses, and men of the greatest penetration and learning, judge if a creature, on the fabric of which there .plainly appears so much art, order, contrivance, and wisdom, nay, in which is seen the hand itself of the Omniscient God, could possibly be the pro- duction of chance or rottenness." This observation refers to the idea formerly entertained almost universally, that the Maggots, which make their appearance in the midst of decomposing matter, are the results or products of that decomposition. Ex- periments devised for the purpose, however, have clearly shown, that there is here no exception to the general rule ; for that, if the parent Insects be carefully excluded, no maggots will make their appearance in a decomposing mass of any description. — Of the voracity of the larvae, and the rapidity with which they undergo their transformations and propagate their kind, some idea may be formed from the estimate of Linnaeus, — that three Flesh-flies and their progeny would devour the carcass of a dead Horse more speedily than a Lion would do. If this estimate is at all exaggerated, it is probably not much so. Hence we see the vast importance of these Insects in the economy of Nature ; for they are called into existence just in proportion to the demand for them, — the eggs of the parent not being developed, unless they are deposited in a fit situation, so that the number of individuals will not be increased unless there is matter for them to feed on, — whilst, on the other hand, the rapidity of the growth and metamorphoses of these Insects is greatly increased, by the warmth that promotes the decomposition of the sub- stances, which they are destined to remove. 204 (ESTRIDJE, OR BOT-FLIES. 799. The CESTRID^E, or Bot-flies, are a family very remark- able in regard to their structure and habits. The perfect insects resemble large Meat-flies in form, are very hairy, and have these hairs coloured in rings, like Humble Bees ; but they are seldom seen, the duration of their lives being very short in this condition. Their chief peculiarity consists in the ab- sence of any proper mouth in the Imago and in the peculiar habitation of the Larva. This is always found in living animals, — its situation, how- no. 53o.-eing interposed between each pair of firm rings or plates. This is obviously required by the condensation of the rest of the integu- ment ; since, if it were otherwise, the body would not have the power of bending in any direction. The legs are covered with the same kind of integuments, and are jointed in a similar manner; each terminates in a single claw or hook. Sometimes two pairs of legs seem to be present on each segment (Fig. 535) ; but this results from the fact, that two adjacent segments are soldered (as it were) together, so as to appear but one, — as is made evident by the existence of a similar doubling of all 535. — I'OLVDKb.Mt S. ,, , the other organs in each division, and by the existence of a deep groove which runs across it, marking the line of union. The first segment or head is furnished with a pair of compound eyes, resembling those of Insects, but less complicated in their structure ; and also with a pair of jointed antennae. The mouth is adapted for mastication ; and possesses a pair of mandibles, followed by a lower lip, and by a pair of appendages somewhat resembling the feet-jaws of Crus- tacea. On the side or under surface of the body may be observed a row of minute pores, a pair usually existing on each segment ; these are the stigmata, or apertures for the admission of air to the respiratory organs, which consist of trachea or air-tubes resembling those of Insects. These tracheae, however, do not so completely unite into a system, as in that class (§ 677) ; for those of the several segments have but little communication with each other. — The character of the other organs strongly resem- bles that of the similar parts in Insects, though not so highly developed. The alimentary canal runs straight, or nearly so, from one end of the body to the other ; and possesses a few glandular appendages, in the form of a long tube very imperfectly developed. The circulation is carried on by the aid of a long dorsal vessel, which extends along nearly the whole length of the body. The nervous system presents a multiplication in its ganglionic cen • tres, corresponding with the multiplication in the number, and GENERAL CHARACTERS OF MYRIAPODA. 211 the similarity in the character, of the segments. — The Myriapoda cannot be said to undergo any proper metamorphosis, like that of Insects and some Crustacea ; since the young one, at its ex- clusion from the egg, possesses the form and most of the general characters of the parent; but there is a gradual increase, during the period of growth, not merely in the size of the body, but in the number of segments and legs ; and in one division of the class (the lulidae), the young, when it first issues from the egg, is altogether unprovided with legs, but h • — «,. forms a white mass, which FIG. ^^TRANSFORMATIONS OF IULTO»; has been called b ^ a, b, c, successive stages. J Fabre the pupoid body. Within this the young lulus is formed ; and when it casts off this covering, it possesses only three pairs of legs, the number of these organs increasing with each change of skin. A considerable number of inoultings takes place before the animal acquires its adult characters ; and this does not happen, in some species, until after the lapse of two years. 806. This Class is divided into two Orders, which differ con- siderably from each other in form and development. I. CHILOPODA, consisting of the Centipedes and their allies ; in which the body is flattened, and the legs well developed, constituting the principal instruments of locomotion. They run with facility ; and are carnivorous in their habits. II. CHILOGNATHA, consisting of the lulus or Millepede, and its allies ; in which the body is cylindrical, and the legs less developed. They move slowly ; and feed upon decomposing organic matter. ORDER L— CHILOPODA. 807. This Order is the one, in which the greatest resemblance to Insects may be traced. It consists of the Centipede and other carnivorous Myriapods, possessing strong and active limbs, usually varying in number from fifteen to twenty-one pairs, although some species possess a much greater number ; by the aid of these they can run with considerable rapidity, and they are 212 ORDER CHILOPODA ; CENTIPEDE AND ITS ALLIES. •ible, owing to the flexibility of their long and jointed bodies, to wind their way with facility among the lurking-places of Insects, against which they carry on an unrelenting warfare. Of their FiG. 537. — SCOLOPEN'DRA, OR CENTIPEDE. carnivorous propensities, the structure of the mouth affords suf- ficient evidence. It is provided, not merely with a pair of horny jaws resembling those of Insects, but with a pair of strong sharp claws, formed by an enlargement of the second pair of logs, and perforated at the top with a minute aperture, through which a venomous fluid is probably instilled into the wounds made by them. Small insects seized in these claws are seen to die very speedily; and in warm countries the bite of the large species of Centipede is a source of great irritation to man, — being reputed to be more injurious than that of the Scorpion, although it is seldom fatal. The application of Ammonia (Hartshorn) is the most effectual remedy for the pain of the bite; and the internal employment of the same remedy seems the best antidote to the effects of the poison upon the constitution. The last pair of legs usually undergoes some modification in this Order ; being directed backwards so as to form a kind of double tail ; and not being used for walking, except when the animal is walking backwards. The European species of this Order seldom exceed three inches in length ; but they are by no means uncom- mon, if sought for in the right situations. They frequent dark places, hiding themselves under stones, beneath the bark of trees, in the ground, and in the hollows of ripe fruit, — situations that are the resort of the Insects on which they feed. The tropical species not unfrequently attain FIG. 538 — a, LITHOBIUS FORCIPATUS ; 6, GKOPHILUS LONGICORNIS. ORDER CHILOGNATHA; — MILLEPEDE, ETC. 213 a length of from twelve to fifteen inches ; and it is stated by Ulloa, that they have been seen at Carthagena exceeding a yard in length and five inches in breadth, and that the bite of these is mortal. It is doubtful, however, whether this statement can be fully relied on. Some of the species are exceedingly elongated, and almost filiform (Fig. 4386) ; and of these some are phospho- rescent in the dark. ORDER II.— CHILOGNATHA. 808. This Order, consisting of animals having a general resem- blance to the lulus or common Millepede, is the one most nearly allied to the Annelida, not merely in external form, and in the imperfect development of the legs, but also in the structure of the internal organs. The body of the lulus (of which one of the commonest species is known as the Gaily- worm) is long and cylindrical ; its number of segments is between forty and fifty ; and many of these bear two pairs of almost thread-like legs, which arise close to the middle line, along the inferior surface of FIG. 539.— IULUS. the body. These are scarcely large or strong enough to support its weight; so that the animal moves but slowly, and seems rather to glide or crawl, like a serpent or a worm, than to walk. "When at rest, the body is rolled up in a spiral form ; so that the feet, being concealed in the concavity of the spire, are protected from injury; whilst the firmness of the rings of the body enables them to resist consider- able pressure. — The mouth of the lulidce strongly resembles that of the Larvae of many Insects, being fur- nished with a pair of stout horny mandibles, with $}iarp toothed edges ; and by means of these, they are enabled to divide with facility FIG. 540.— IULUS, with the body coiled up, and the front of the body unrolled, with the an- tennae magnified. 214 IULUS, POLYDESMUS, G^OMEHI8. the portions of decaying vegetable matter, on which they usually feed. These animals are very harmless to Man, not being pos- sessed of any poisonous organs ; and they may be regarded as positively benefiting him by the removal of substances whost> decay would otherwise be noxious. The common lulus of this country seldom much exceeds an inch in length ; but there is a South American species, lulus maximus, which attains the length of seven inches. — The Polydesmus (Fig. 535) corresponds with the lulidse in general structure and habits, but has the body remarkably flattened. — The Glomeris bears a strong resem- blance to the Woodlouse (§ 873), in its oval form, and its habit of rolling itself into a ball ; it is also remarkable from its small number of segments, those of the body being only twelve, as in Insects. The under surface of • the body, which is concave, has a row of small scales on each side, which has been compared to the lateral lobes of the Trilobites and some of the Isopod Crus- tacea, Altogether the resemblance of this animal to that group is very striking ; the chief difference being in the nature of the respiratory organs. — The animals of this Order are remarkable for their power of emitting a dis- agreeable odour, when they are alarmed. This seems to result from a peculiar secretion, poured out from the stigmata or respi- ratory orifices ; and it may be regarded as a means of defence, which replaces the poison apparatus of the Centipedes. MAEOINATA. 215 CHAPTER XI. OF THE CLASS OF ARACHNIDA. 809. THIS class is composed of Articulated animals, which have a great analogy with Insects, and which are equally fitted to live in the air ; but which are distinguished from them at the first glance, by the general form of the body, and by the number of limbs ; and which differ also from those animals, in several important particulars of their internal structure. All the Arach- nida have the head united with the thorax, and are destitute of antennae ; they have four pairs of legs and no wings ; most of them breathe by means of air-sacs, instead of by pro- longed tracheae ; and nearly all of them have a complete circulating apparatus. 810. The tegumentary skeleton of Arachnida is generally less firm than that of Insects ; and their body is composed of two principal parts, nearly always distinct : — one called the cephalo- thorax, because it is formed by the head and the thorax united into a single mass r the other termed the abdomen, and com- posed sometimes of a series of distinct rings (such as we see in the Scorpions — Fig. 554), and sometimes of a soft globular mass, without any evident divisions (as is the case among the ordinary Spiders— Fig. 549). 811. The organs of locomotion are all fixed to the cephalo- thorax, and consist of eight legs, very similar to those of Insects, and nearly always terminated by two hooks. In general their no. 542.— MTOALE. 216 ORGANS OF SENSE IN ARACHNIDA. length is considerable and they easily break ; but, as amongst the Crustacea, the stump, after being healed, produces a new limb ; which grows by degrees, and becomes similar to the one of which the animal had been deprived. The Arachnida never present any vestige of wings : and their abdomen is always entirely destitute of locomotive appendages. 812. Upon the anterior portion of the cephalo- thorax, we find the mouth and eyes. These last organs are always simple, and of considerable number. We may generally count eight, and in each of them may be distin- guished a transparent cornea, behind which is found a crystalline lens, and a vitreous humour ; then a retina formed by the termination of an optic nerve, and an envelope of colouring matter. — Nothing is known regarding the instruments by which the sense of hearing operates in the Arachnida ; but there are numerous proofs of the existence of such a faculty amongst these animals ; and it would even appear that certain of them are sensible to the charms of Music. — The sense of touch is exercised principally at the extremities of the legs, and by the appendages with which the mouth is furnished. FIG. 543. Fra. 544. — SUCTION OF THE CEPHALO-THORAX OF A M VGALE, showing the arrangement of tho nervous sytem : ct, cephalotborax ; m, mandible ; g, moveuble hook which terminates it ; b, mouth \'tr, oesophagus ; e, stomach ; aft, origin of abdomen ; c, cephalic ganglion ; t, ganglionic mass of the thorax ; ca, cords which unite it to the abdominal ganglia ; no, optic nerve ; y, eyes. 813. The nervous system of the Arachnida presents very great differences ; sometimes (amongst the Scorpions for ex- NERVOUS SYSTEM AND HABITS OF ARACHNIDA. 217 ample) it is composed of a series of eight ganglionic masses, united together by double cords of communication, and forming a chain extended from one end of the body to the other, in nearly a uniform manner ; in other instances (as amongst the Spiders, &c.) we find all the ganglia of the thorax united into a single mass (t, Figs. 544 and 546), whence two cords proceed backwards, which go to a single abdominal ganglion. In other respects, the general arrangement of these parts is always the same. The anterior ganglia, situated before or above the oesophagus, and most commonly considered as representing the brain of these animals, give origin to the optic nerve in front, and are con- tinuous behind with the collar of nerves surrounding the oesopha- gus ; the other ganglia are situated below the alimentary tube, and send nerves to the limbs, to the appendages of the abdomen, &c. 814. The Arachnida are carnivorous, but in general confine themselves to sucking the juices contained in the bodies of their victims ; and in order to enable them more easily to effect the capture of animals of whose strength they would be afraid, Nature has endowed many of them with a poisonous apparatus. The greater part are supported on Insects, which they seize whilst alive ; some of them, however, live as parasites. Among the first, the mouth is supplied with a pair of mandibles, furnished with moveable hooks, or formed like a pair of pincers, — with a pair of thin or lamellated maxillae, each bearing a large feeler more or less resembling a leg, — and with a lower lip. Amongst the parasitical Arachnida, the mouth has p the form of a small trunk, from which there issues a kind of lancet formed by the maxillae. 815. The moveable hook of the ma mandibles has a small opening near its _* extremity, which is the orifice of the excretory canal of the poison-gland al- labium; ma, maxiii*; P, * . , , .. ,. ; ", . . , maxillary palpi; m, man- read y mentioned; and the liquid, which dibies; g, hook terminating it pours into the bottom of the wounds the mandibles- made, with the mandibles, almost immediately causes the destruc- tion of the animal attacked ; but it is too weak to injure Man. 2 i8 POISON- APPARATUS, AND DIGESTIVE SYSTEM. 816. Certain of the Arachnida are provided with another poison apparatus, destined for the same use, and serving equally as a weapon of defence : such is the hook by which the abdomen of Scorpions is terminated (Fig. 554). This sting has beneath its point several openings, which communicate with a poison- gland ; and the sting of these Arachnida often proves mortal, even to animals as large as Dogs. The large Scorpions of warm countries are fatal even to Man, but the sting of the species which inhabit Europe never appears to be m *tal ; there usually results from it a local inflammation more or less violent, accom- panied by fever and depression, and sometimes by vomiting, pains in the whole body, and trembling. To overcome these attacks, physicians advise the use of ammonia (or spirit of harts- horn), administered internally as well as externally ; and the application of emollient substances to the wound. 817. The intestinal canal is generally very simple ; but has sometimes csecal appendages, which penetrate even into the interior of the limbs. In general, tubes analogous tothewrinary po ab po t Fio. 546. — ANATOMY OF MYOALE : ct, cephalothorax opened below, and giving attach- ment to the limbs, whose first joints are exhibited ; pa, legs of the 1st pair ; p, palpi ; m, mandibles ; afe, abdomen ; t, thoracic nervous mass ; a, abdominal ganglia ; po, respiratory sacs ; t, stigmata ; I, leaf-like folds in the interior of one of these laid open ; ov, ovaria ; or, orifice of oviducts ; ma, muscles of the abdomen ; an, anus ; /, spinnerets. vessels of insects open into the intestine near the anus; but amongst some of the Arachnida, such as the Scorpions, there exists a liver composed of four glandular clusters. It is also in RESPIRATION AND CIRCULATION OP ARACHNIDA. '219 the neighbourhood of the anal opening, that we find the secret- ing glands of the silky matter; and also the spinnerets, by whose aid several of the Arachnida weave for themselves webs, which are often very extensive and of extreme delicacy. 818. The respiration of the Arachnida is aerial, like that of In- sects, and is sometimes effected by means of tracheae ; but among the greater part of these animals, and especially amongst the Spiders and Scorpions, it is concentrated in certain vesicles lodged in the abdomen, and called pulmonary sacs. These last organs have in their interior a multitude of membranous plates, arranged like the leaves of a book : and they thus bear a stronger resem- blance to internal gills, than to true lungs. Each sac receives the air by an opening situated on the lower side of the abdomen ; and there are sometimes two, sometimes four, or even eight of these stigmata. Certain Arachnida possess at the same time both pul- monary sacs and tracheae ; the Segsstricz arc thus formed. Others, such as the Pseudo- Scorpions and Mites, are provided with tracheae only. These tubes have the same structure as in Insects ; and the air a1 penetrates to them by two very small stigmata, situated on the lower side of the „ abdomen. 819. Tho blood is white among all the e animals of this class. The pulmonary Arachnida are furnished with a complete circulating apparatus. The heart, situated on the back, has the form of a long vessel, and gives origin to different arteries ; the blood after having traversed the body is returned to the pulmonary sacs, and arrives , ,, , ., * ,, ... at the heart after following a COUrse Similar to that which it traverses in the Crustacea (ANIM. PHYSIOL. § 292). Amongst the Arachnida whose respiration is effected only by the aid of traohece, the apparatus for circulation is but little developed ; there appears to be only a simple dorsal vessel, without arteries or veins. 820. The Arachnida lay eggs like Insects ; and the male differs in general from the female in the form of its maxillary a, border of the abdomen , <;, heart ; ar, large artery, nary vessels. 220 INSTINCTS OF ARACHNIDA. palpi, whose use appears to be very important ; a great number of these animals envelop their eggs in a cocoon of silk ; and sometimes the mother remains with her young family to protect it, and even carries the young ones on her back when they are too weak to walk. All these animals undergo several changes before they arrive at adult age ; and certain of them experience a species of metamorphosis, for there are some, whose limbs consist at first of only three pair, and which acquire a fourth at a period more or less advanced. 821. The Arachnida are endowed with varied instincts, which are sometimes notless remarkable than those of Insects; and weare perhaps even to attribute to them higher faculties; for some animals of this class are capable of undergoing a kind of education, and give evidences of a certain degree of Intelligence. Several of them use particular stratagems to carry off their prey ; and others display singular industry in the construction of their habitations. We have elsewhere had occasion to speak of the remarkable nest of the Mygale ( ANIM. PHYSIOL. § 700) ; and the webs which our garden Spiders spread with such admirable regularity, are equally curious. The silk with which these animals thus con- struct retreats for themselves, spread snares for their prey, and form cocoons for their eggs, is secreted by an apparatus situated in the posterior part of the abdomen. This apparatus consists of several bundles of vessels, twisted together, and terminating in minute apertures, which are pierced at the summit of four or six conical or cylindrical projections, called spin- nerets, and situated at the end of the tail. The gluey matter thrown out through these pores, acquires consistency by its contact with the air, and consists of threads of an Fi«. 548.— NEST OF MYGAI>K. extreme fineness, and a length not less remarkable ; by the help of its feet, the animal collects a number of these threads into a single cord ; and each time that, in balancing itself, the spinnerets touch the body upon which it rests, it there INSTINCTS AND CLASSIFICATION OF ARACHNIDA. 221 fastens the end of one of these threads, of which the opposite ex- tremity is still inclosed in the secreting apparatus, and of which it can consequently increase the length at pleasure. The colour and thickness of these threads vary greatly ; a Mexican Spider forms a web composed of red, yellow, and black threads interwoven with astonishing skill ; and it has been calculated that ten thou- sand threads from the pores of a single spinneret of some of our common Spiders do not equal in thickness one of our own hairs ; whilst among other species inhabiting warmer climates, they form such strong webs, that they are sufficient to stop small birds, and even Man has to use some effort to break them. The manner in which Spiders employ their skill in working, is subject to no less variation ; some of them are satisfied with spreading their threads irregularly ; others weave a web, whose meshes are of extreme regularity. Sometimes we see them motionless in the middle of their web, watching for their prey ; at other times they conceal themselves in a retreat, which they construct very near, and which has in some instances the form of a silky tube, in others that of a small cup. 822. The ARACHNIDA may be divided into two orders, from differences in the organs of respiration and circulation. I. The Pulmonary Arachnida ; which are principally charac- terised by the existence of pulmonary cavities, and of a vascular apparatus ; they have six, eight, or even more eyes, and we also find two, four, or eight stigmata on the under part of the abdomen. The general form of these animals varies ; some, as the Spider, have a globular body, with spinnerets at its extremity, and the palpi small ; — whilst in other instances, as the Scorpions, the body is lengthened, and composed of several rings, the palpi large, ex- tended like arms, and armed with pincers ; and the abdomen is not terminated by spinnerets, but by the poisonous apparatus. II. The Tracheary Arachnida ; which have no pulmonary sacs, but breathe by tracheae like Insects, and appear to have no com- plete vascular apparatus for the circulation of the blood. Some of them have no eyes ; and amongst those which possess these or- gans, we never find more than two or four. Some of these animals very much resemble Spiders; others have the mouth formed for sucking, and constitute the family of Acaridte, or Mites. VOL. II. R ORDER PUIMONARIA. — SPIDERS, ETC. ORDER I.— PULMONARIA. 823. By the characters just now .stated, this order may be divided into two sections ; — the ARANEIDA, or Spiders, having small simple palpi, not terminating in pincers ; and the PEDI- PALPI, or Scorpions and their allies, having very large palpi, which terminate in pincers or large hooks. 824. Section I. ARANEIDA. The Arachnida of this group all agree, more or less closely, with the common Spider, in their form and structure. Their cephalothorax appears as if composed of but a single segment, and is covered with a sort of horny buckler, usually of oval form ; the abdomen is appended to it by a very short footstalk, and usually consists of a soft and tumid mass. The eyes are nearly always eight in number ; although there are sometimes but six. The mandibles terminate in a very sharp moveable hook, which is pierced near its extremity by a small aperture, serving as a passage for the poison secreted by a gland lodged in the preceding joint. The legs are inserted almost in a circular manner around the cephalothorax (Fig. 546) ; they are all of nearly the same form ; and each of them is composed of seven joints, the last being armed with two hooks, which are commonly toothed like a comb. The pulmonary sacs in this order are usually only two in number, or may even be reduced to a single one ; they are placed near the base of the abdomen, and their position is indicated externally by a brownish or whitish spot. All the members of this section are provided with spin- nerets ; but it is only in a small number that we find the power of constructing silken webs of any great extent. The ARANEIDA are divided by M. Walckenaer into families, according to the arrangement of the mandibles and eyes, which corresponds very remarkably with their respective modes of life.* These families, and their principal subdivisions, are as follows : — * For this reason, the classification and nomenclature of Walckenaer, although now somewhat antiquated, are retained here. CLASSIFICATION OF SPIDERS.— HUNTING SPIDERS. 223 .*;, hiding iu holes and fissures. I. VENANTES, incessantly TUBICOLJE, inclosing themselves in silken tubes. running or leaping about | CELLULICOLJE, sheltering themselves in small the vicinity of their abode, J cells. to chase and catch their I CUKSORES, running swiftly to catch their prey. prey. | SALTATORES, leaping and springing with agi- (^ lity to seize their prey. II. VAGANTES, wandering r abroad, and incessantly i LATERIGRAD^E, walking and running sideways looking out for prey. No^ or backwards; occasionally throwing out fixed residence except at threads to entrap their prey. the period of oviposition. L III. ERRANTES, prowling ^NITIDELJE, going abroad, but making a web for about the neighbourhood I their nests, whence issue threads to entrap of their nests, or near the) their prey. threads which they throw ] FILITEL^E, going abroad, but spreading long out to catch their prey. threads of silk about the places where they (^ prowl, in order to entrap their prey. fTAPiTELTE, spinning great webs of a close tex- ture, and dwelling therein to catch their prey. IV SEDENTES SDinnine ORBITEL.E, spreading abroad webs of a regular large webs to entrap their and °Pe.n te?tu™> either circular or spiral and pregy, lying in wait ?n the \ ThT^ m *" ""^ " ^ ^ ^ ^ middle or at the side. „ catch their P1^ , . ItETiTELJE, spinning webs of an open meshwork, and of an irregular form, and remaining in the L middle or on one eide to seize their prey. V. NAT ANTES, swimming in r water, and there spreading ! AQUITEL^E, spreading filaments in the water to their filaments to entrap j entrap their prey. their prey. 825. The first family, that of the VENANTES, or Hunting - Spiders, may be naturally divided into two groups ; the first being more sedentary, and the second more active. At the head of the first group stands the tribe of LATEBRICOL^E, which consists of the genus Mygale (Fig. 542) and its allies ; these are the largest of the whole family, some of them occupying, in a state of repose, a circular space of six or seven inches in diameter. They form their nests in the slits of trees, beneath the bark, in the cavities of stones and rocks, or on the surface of the leaves of various trees. Some of them burrow into the ground, as has already been stated (§ 821, and ANISI. PHYSIOL. § 700). The Mygale spins a sort of cocoon around its eggs, enclosing a hundred or more ; they are hatched within it, and the young undergo their first changes before quitting it. The various species of this group nre inhabitants of tropical and the warmer temperate climates ; 224 MYGALE. — RUNNING SPIDERS. it is only in the former, that we find those of largest size. Amongst these, some of the large South American species have been said, by Madame Merian and others, to devour small birds ; and although little credit has hitherto been attached to these statements, yet from an account recently furnished by Mr. Bates to Mr. Adam White, of the British Museum, and communicated by the latter gentleman to the Zoological Society, they would appear to have some foundation in fact. Mr. Bates says, that he, on one occasion, surprised a Mygale in the act of preying upon a small Finch, which had been entangled in a web near the root of a tree ; and he adds, that from the multitude of these spiders which exist upon the dry plains in the neighbourhood of Para, on which insects are very scarce, he feels convinced that they must feed upon the young and eggs of the small ground birds which are their co-inhabitants of these wildernesses. — The TDBI- COL^. and CELLULICOL^E are not sufficiently distinct from the preceding, to require particular notice. They are mostly of smaller size, and inhabit temperate climates, where they may be con- sidered as representing the Mining Spiders. 826. The tribes of CURSORES, or Runners, and SALTATORES, or Leapers, forming the second division of the Hunting Spiders, are distinguished by the activity with which they pursue their prey. The former, which are sometimes called Wolf- Spiders, have the legs adapted for running, and live mostly upon the ground. Those of the genus Lycosa dwell in holes which they have formed, lining their inside with silk, and increasing their size as they grow. Some of them take up their abode in holes of walls, where they make silken tubes ; the outside of which they cover with earth or sand, and in which they moult or hybernate, having first closed the entrance. The females also lay their eggs in these tubes ; enclosing them in a silken cocoon, or egg- case, which they carry about with them when they go out to hunt. The young ones fasten themselves, as soon as they are hatched, upon the body of their parent ; and there remain attached, until they are sufficiently strong to seek their own food. These Spiders are very voracious, and defend their habita- tions and young with great courage. A species of this genus TARKNTL'LA. — LEAPING SPIDERS. 22o the Tarentula,) — so named from the city of Tarentum, in Italy, in the neigh hourhood of which it is common, — is very celebrated on account of its reputed venomous powers. Like all the Spiders, it has a poison-gland in its mandibles; but the idea that its wounds are followed by death, or by a complaint termed Tarantism, which can only be cured by the aid of music and dancing, has originated in the imagination only. — Some species of the genus Dolomedes live upon the tops of trees, upon the leaves of which they make a funnel-shaped silken nest ; whilst others inhabit plants in the neighbourhood of water, on which they find their prey, — running upon its surface with surprising quickness, and even entering it without being wetted. — The Spiders of the tribe of SALTATORES, or Leapers, have, as might be anticipated from their name, the legs fitted rather for leaping than for running. One of these is very common in summer upon walls and windows exposed to the sun ; and its habits may be watched with much interest. It moves in short leaps, and stops suddenly at intervals, raising itself upon its legs, as if to survey the neighbourhood. When it discovers a fly, or especially a gnat, it approaches it cautiously until within leaping distance ; when it darts upon it, — not fearing to take even a perpendicular leap, because it always at the same time suspends itself ^ a thread, which it winds off as it advances. This thread also serves to suspend it in the air, and enables it to mount up again to the spot from which it leaped, or to sustain it whilst the wind carries it from place to place. Many species of this group construct, amongst leaves, under stones, &c., silken nests, in the form of oval sacs, open* at each end; into which they retire in order to take rest, to moult, and to take refuge against the inclemency of the weather. If menaced with danger, they quit these retreats, and run off very rapidly. Some species construct, with the same material, a kind of tent, which serves as the birthplace of their posterity, and in which the young reside for some time with their parent. 827. The family VAGANTES, or Wandering Spiders, consists of the single tribe LATERIGRADA ; the name of which (meaning Side- Walkers) expresses the curious power which they possess, 226 WANDERING SPIDERS. — PROWLING SPIDERS. of moving sideways. They conduct us towards the web-spin- ning Spiders, in using their silken threads, not only for the construction of habitations for themselves or of envelopes for their eggs, but also for the purpose of entrapping prey. The threads, however, are not arranged with any regularity, but are laid singly. These Spiders generally remain at rest, with the legs spread out, upon the leaves or stems of plants ; running, however, with great rapidity, in pursuit of their prey, when it comes within their reach. Others, however, live in rocky places ; and have the feet so formed, that they can adhere even to very smooth surfaces, in any position of their own bodies. They usually construct very elaborate cocoons for the protection of their eggs. Those which live among plants affix the cocoons to the leaves, and draw together their edges so as to conceal them. Those, on the other hand, which live upon rocks, usut My conceal the cocoon within their own dwelling-place ; which is an oval conical tent, something like a Limpet in form, attached at its base to the rock, but having an aperture at each end, furnished with a kind of valve through which the animals go in and out. The outer covering of this tent is composed of a sort of yellowish taffety, thin (like the skin of an onion), but resist- ing whilst the inner covering is soft and pliant. 828. The Spiders of the family ERR ANTES, or Prowlers, aro divided into two groups, chiefly according to the situation in which they throw out the silken lines for the entanglement of their prey. The first tribe, that of NITITEL^E, contains species that only prolong these threads from their nests, which are formed under stones in holes of walls, the hollows of leaves, and similar situations. These species much resemble those of the last tribe in their habits ; but differ in many points of structure. — In the second tribe, the FILITELJE, the threads are spread about the places, in which these Spiders prowl in pursuit of their prey. Among these, the Clotho, which inhabits Egypt and the South of Europe, is remarkable for the curious habitation which it constructs for its young. This is a kind of limpet-shaped cocoon, about an inch in diameter, of which the circumference has seven or eight festoons ; the points of these festoons oeiug PROWLING SPIDERS ; CLOTHO. SEDENTARY SPIDERS. 227 alone fixed to the stone by means of threads, whilst the edges are left free. This singular tent is at first composed of only two folds, between which the Spider takes its station. But subsequently it adds additional folds ; and when the period of reproduction arrives, it weaves another apartment, of a softer texture, expressly for the reception of the sacs of eggs, and of the young when hatched. The inside of its habitation is singularly clean. The bags in which the eggs are placed, are about one-third of an inch in diameter ; and there are from four to six of them in each habitation. The eggs are not deposited until the end of December or January ; and they are enveloped in fine down, to guard them from the cold. The parent creeps in and out beneath the edges of the festoons ; and supplies her young with food, for some time after they are hatched. When they are able to dispense with maternal cares, they quit their common habitation, and form separate abodes; and the parent dies within her tent. 829. The next family, SEDENTES, or Sedentary Spiders, con- tains all those species with which we are most familiar, from the annoyance they cause us by the construction of their webs in our houses and gardens. — Of the first tribe, TAPITEL.E. — which con- struct a sort of tapestried web of close texture, within which they dwell and wait for their prey, — the common House-spider is a characteristic example (Fig. 549). — The Spiders of the second tribe, ORBITEL^E, have the abdomen larger, softer, and more coloured than the preceding ; they make their webs with regular meshes ; arranged in concentric circles crossed by straight radii ; and they usually remain stationary in the centre, in a reversed position (Fig. 550). Many species, however, construct for themselves a cavity or cell, which is sometimes horizontal and sometimes perpendicular, near the edges of the net. Of this group, the genus Epeira is the principal ; of which several species abound in our gardens, especially during the autumn. The eggs are deposited by the parent at the commencement of cold weather, in angles of the ceilings of rooms, passages, &c., near gardens ; they are enveloped in a loose white web ; and are hatched in the spring of the following year. Some species of 228* IXODID.E.— GAMASID^.— HTDRACHNID^. skins of animals whose blood they suck. They are usually of a flattened, round, or oval form ; but they often acquire a very large size by suction, and become distended like a blown bladder. They are found in thick woods, abounding in brushwood, briars, &c., and attaching themselves to plants with the two fore legs. They fasten upon dogs, cows, horses, and other quadrupeds, and even upon reptiles ; and they bury their suckers (which are often furnished with minute recurved hooks, as in the Ixodes, Fig. 561), so firmly in their skin, that they can hardly be detached by force, — the portion of skin to which they are attached coming FIG. 561. — IXODES FIG. 562. a, HYDRACHNA GLOBULV8 ; PLUMBEUS, AND ITS b, magnified ; e, young larva ; d, pupa. BEAK, magnified. away with them. It is probably the young of a species of this group, which is commonly known as the Harvest-Bug ; this is very common in the autumn, upon grass or other herbage ; and insinuates itself into the skin at the roots of the hair, producing a very painful irritation. In this state it possesses only six legs. — The GAMASID^}, or Beetle-Mites, resemble the Ixodidce in many respects, and like them are parasitic upon various animals ; they are distinguished from the Ixodidae by their free, filiform palpi, which do not form a sheath for the rostrum as in the Ticks. They usually live in the nests of their victims, coming forth from their hiding places during the night. One species is common in bird-cages, where it often does serious injury to our little feathered favourites. 840. In the preceding families, consisting for the most part of parasitic animals, the majority of the species are destitute of eyes ; in the remainder of the typical Acarina these organs are present. — The HYDRACHNID^:, or Water-Mites, have the legs TROMBIDIID^.— ORIBATID^E.— SIMONEID^E. 229 covered with hairs in such a manner as to adapt them for swim- ming, and after reaching maturity they are always found free in the water. They undergo a more complete metamorphosis than any other Mites ; the larvae have six legs and apparently a distinct head ; and the pupa: are perfectly quiescent, and attach themselves to the bodies of aquatic insects or Mollusca. — The TROMBIDIIDJE, or Ground-Mites, are distinguished by having the palpi converted into little raptorial organs. They live upon the ground in crevices, and run fast. The well-known Scarlet- Mite of our gardens belongs to this family. They are capable of spinning little webs for the protection of their eggs ; and some species are very injurious to plants in hot-houses and frames, by spinning webs over their leaves. The young are parasitic, usually upon insects. — The BDELLIDJE, which live amongst damp moss, and greatly resemble the preceding in their mode of life, are distinguished by having the body apparently divided into two parts, and the rostrum and palpi of great length : — whilst the ORIBATID./E, or Plant-Mites, are distinguished from all the other Acarina, by the glassy hardness and brittleness of their skins, and by the adaptation of their mandibles to the purpose of biting ; their food consists of vegetable matters, especially the leaves of mosses, amongst which plants they are usually to be found. 841. Besides these families of undoubted Mites, there are three others which are now arranged with the Acarina by most authors, but which present such peculiar characters, that their title to such a position may appear somewhat doubtful at the first glance. The first of these, the SIMONEID^E, includes a curious minute parasitic animal, the Simonea folliculorum, which takes up its abode in the follicles of the human skin, — especially on the nose. In the young state it is a small, elongated, worm-like creature, furnished with three pairs of rudimentary feet on the widened anterior part of the body ; but as it in- creases in age the elongated hinder part, or abdomen, gradually becomes shorter, and a fourth pair of little feet makes its appear- ance. The structure of the mouth resembles that of the Mites. These curious little parasites have not been discovered many VOL. II. S 230 LINGUAT JLIDJE. — MACROBIOTIDJE. years ; they are obtained by carefully squeezing out tlie contents of pimples. — The LINGUATULIDJB, or Tongue-worms, present far less resemblance to the ordinary Acariua; they are elongated worm-like, jointed creatures, which inhabit the lungs and frontal sinuses of some Mammalia and the lungs of a few Reptiles. Their only exter- _^~~-!-r-rTr '^^TST^*^ na^ oroans consist *ux&3ZZu3^^ '^ of two Pairs of very curious hooks placed near the mouth. Until very lately these singular parasites were placed amongst the Intestinal worms ; but recent researches into their mode of development have shown that they are most nearly allied to the Arachnida. The young, when just hatched, are little, oval, mite-like creatures, furnished with four short, jointed legs, and with the rudiments of a mouth at the anterior ex- tremity. With age the body becomes greatly elongated and distinctly divided into segments, whilst the vestiges of the four limbs are to be found in the singular apparatus of hooks above mentioned. — The MACROBIOTID^;, or TARDIGRADA, forming the third of these doubtful families of Acarina, include a number of minute creatures, well known to microscopic observers as Sloth or Bear- Anifhalcules. They are usually found in moss or in fresh water, and have usually been placed with the Rotatorial Ani- malcules. Their form is usually an elongated oval, and they are furnished with four pairs of short legs, each of which usually bears four little claws. The last pair is situated at the hinder extremity of the body. The mouth forms a sort of rostrum. Little or nothing is known of their habits ; and the most singular circumstance connected with them is their power of returning to life when moistened, after they have been for a considerable time in a dry and apparently lifeless state. They may often be found amongst the dust which collects in the gutters on the roofs of houses. CHAPTER XL CLASS OF CRUSTACEA. 842. CRUSTACEA are Articulated animals, respiring bybranchue or external gills, or by the general surface, and possessing a circulating apparatus, and separate sexes. Crabs and Lob- sters are the types of this group ; but a great number of animals of a much less complicated structure, and of a different external form, are also classed with these ; for as we descend the natural series formed by these animals, we see the same general plan of structure gradually modified and simplified. The lowest Crustacea are even so imperfect, that they can only exist, attached like parasites, on other animals : whence most Natura- lists have placed them with the Intestinal Worms. 843. The tegumentary skeleton of Crustacea generally pos- sesses a very considerable degree of firmness. It has nearly always a stony hardness ; and indeed contains a very consider- able proportion of carbonate of lime. We may look upon this solid envelope as a kind of epidermis ; for beneath it we find a membrane like the true skin of higher animals ; and at certain times it detaches itself and falls off, in the same manner as the epidermis of Reptiles separates itself from their bodies (§ 471), and as we have also seen the enveloping membrane of the larvae of Insects renew itself several times. We can easily understand the necessity of this change, in animals whose whole bodies are inclosed in a solid case ; which, not being able to grow like the interior parts, would oppose an invincible obstacle to their development, if it could not be thrown off, as soon as it lias become too small to lodge them commodiously. Thus the Crustacea change their skin during the whole time of their growth ; and it would seem that the greater part of these animals grow during their whole life. The manner in which 232 BODY OF CRUSTACEA. — DIVISION INTO SEGMENTS. Fro. 564.— SANimorrER. they free themselves from their old shell is very singular. In general they get out of it without occasioning the least change in its form ; and when they have quitted it, the whole surface of their body is already clothed in a new casing, — but this is still soft, and does not acquire its requisite solidity for some days. 844. The body of Crustacea is composed of a series of rings, more or less distinct. Sometimes most of these segments are simply articulated one with the other, so as to admit of a considerable de- gree of motion, as in the Sand- hopper ; sometimes they are nearly all soldered together, and are only distinguished by furrows situated at their line of juncture ; lastly, in other cases, their union is still more close, and it is only by analogy that we are led to con- sider the trunk, resulting from their juncture, as made up of several rings. Hence result very great differences of form ; and if we compare with each other a Woodlouse (Fig. 565), a Sandhopper (Fig. 564), and a Crab (Fig. 566), we might be at first led to be- lieve them formed according to types en- \\ / tirely different ; but a deeper study of ~=\jjf their structure shows, that the compo- sition of their tegumentary skeleton is essentially the same, and that the dif- ferences lie almost entirely in this, — that most of the rings which are quite distinct and moveable in the Woodlouse, are grown together in the Crab, and that certain analogous parts do not present the same proportions in both animals. Thus in the Woodlouse and Sand-hopper we find a distinct head (c) followed by a thorax composed of seven rings similar to each other (tl £2), and each ring provided with a pair of legs ( p, pp,) ; and at the posterior part of the body we see an abdomen, also composed of seven seg- FIG. 565.— ONISCTJS, OR WOODLOUSE. BODY OF CRUSTACEA. — DIVISION INTO SEGMENTS. 233 FIG. 566.— CANCER PAGURCS, Liim., with the tail of the male, a , and of the female, b. ments (as}, whose size diminishes rapidly, but whose form is nearly the same as in the thorax. In the Crab (Fig. 566), on the contrary, the head is not separated from the thorax ; and it forms, with the whole middle part of the body, but a single mass covered by a large solid buckler called the carapace. The abdomen, at first, escapes observation ; for it is bent down under the thorax, and is of small size. Yet it is easy to show, that in the Crab, as in the Woodlouse, there are seven thoracic rings, and that the cara- pace is not a new part introduced instead of the former, but merely the dorsal portion of one of the rings of the head, so ex- tremely developed as to encroach upon all the neighbouring rings. 845. In other animals of the same class, the general form of the body differs still more widely from those of which we have just spoken. Thus the Limnadice are inclosed between two oval shields, joined like the valves of an Oyster, and it is only after having raised this moveable cuirass, that we first perceive the annular structure of the body (Fig. 598) ; the Cypris (Fig. 603), which abounds in stagnant waters, presents a similar arrange- ment : but the rings of which its body is composed are still more difficult to recognise. The Lernece, which at their adult age present the strangest forms, in the earlier part of their exist- ence possess a regular annular structure (Figs. 609, 610). And lastly, we may advert to the Cirrhopods, in which the characters of annulose animals are so singularly masked, that for many years they were placed amongst the Mollusca ; but which, on first quitting the egg, are completely Crustacean in their character 234 LATERAL APPENDAGES OF CRUSTACEA. (§§ 891 — 898). This comparative study of the teg umentary ske- leton is of great interest as a department of Philosophic Anatomy ; one of whose most important branches has reference to those mo- difications, to which Nature subjects the same organic elements, in order to adapt them to various purposes, and to create different animals from analogous materials ; but the limits we have assign- ed ourselves do not permit us to dwell longer on this subject. 846. The lateral appendages of the different rings constituting the body, are in general very numerous, and present consider- able differences in their conformation and uses ; — both when we consider those in the different parts of the same individual, and when we compare them in distinct species. Those of the first pair are generally subservient to the animal functions, and sup- port the eyes or constitute the antennae ; the next surround the mouth, and serve for the prehension or division of the food ; those of the middle part of the body constitute the legs for loco- motion; and those which are placed behind have various uses, but are generally subservient to respiration or reprodnc- pm FK;. 567. — PRAWN : — as, antennae of the first pair ; ai, antennae of the second pair ; I, laminar appendage covering its base ; r, rostrum, or frontal prolongation of the carapace ; y, eyes ; pm, external foot-jaw ; p , first thoracic member ; p", second thoracic member ; fp, false legs, or swimming members, of the abdomen ; n, tail-fin. tion ; lastly, this long series ordinarily terminates by one or several pairs of members, which serve as fins. 847. The head, or rather the cephalic portion of the body, carries the eyes, the antennae, and the appendages of the mouth. LATERAL APPENDAGES OF CRUSTACEA. 235 It is sometimes divided into several distinct rings, as in the Scillce ; but in general there is no separation, and it is formed of a single piece, which seems to represent seven segments joined together. Sometimes it is moveable, and distinct from the thorax (Fig. 566) ; sometimes, on the contrary, it is joined to this second part of the body, which in its turn is composed of distinct rings, articulating with each other in some species, but in others united into a single mass. 848. Of the antennae, there are nearly always two pair ; and they are generally thread-like, and very much elongated (Fig. 567, as and ai). The legs originate by pairs from the different thoracic rings ; and they often amount to seven pairs, as for example in the Woodlouse (Fig. 565), and Sand-hopper (Fig. 564) ; but in other instances, as we see in Crabs (Fig. 566) and Cray-fish (Fig. 579), their number is reduced to five pairs ; those appendages, which in the former constituted the four anterior legs, being subjected in the latter to other uses, and transformed into organs of mastication (§ 850). There are also very great differences in their structure : in some Crustacea they are leaf-like, membranous, and fitted for swimming only (Fig. 598) ; in others they look like little columns jointed together, and adapted for walking only ; in others, while yet remaining appro- priate to this last kind of locomotion, they are destined to be used also as so many little spades for digging in the earth, and then they are enlarged and laminated at the end (Fig. 568) ; lastly, in others, they end in pincers, and thus become instruments of prehension, at the same time that they fulfil their ordinary functions in locomotion (Figs. 579 and 613). In swimming Crustacea, such as Cray- fish, Lobsters, Prawns, &c. (Fig. 567), the abdomen generally attains a con- siderable development, and ends in a large fin, in such a manner as to become the principal agent in PIG. 568.— HlPPA. 236 NERVOUS SYSTEM OF CRUSTACEA. locomotion ; but in those which are destined to walk rather than to swim, this part is generally very small and bent under the thorax. In the Crabs, for instance, this portion of the body is reduced to almost nothing, and forms a sort of moveable append- age, which is seen on the inferior surface of the body beneath the legs (Fig. 566). 849. The Nervous System of Crustacea consists of a double series of ganglia, situated on the ventral surface of the body, near the central line. In general their number corresponds to that of the distinct segments composing the body ; and the first pair is always placed on the head, in front of the oesophagus, where it forms a sort of brain. The arrange- ment of the thoracic and abdominal ganglia, however, varies con- siderably ; sometimes they are placed at equal intervals, and form, with their cords of communication, a chain extending from one end of the body to the Other ; Sometimes they FIG. 569— NERVOUS SYSTEM OF CRAB (Main) : ca, nrmrnnpli rniP nnnflipr upper part of the shell laid open j a, antennae ; ?,eyes; e, stomach ; c, cephalic ganglion ; wo, optic nerves; co, cesophageal collar; ns, stomato-gastric nerves ; t, thoracic ganglionic mass ; np, nerves of the legs > na, abdominal nerve. more or less closely ; and sometimes they are united, forming a single mass, situated about the middle of the thorax (Fig. 569, t). It may be remarked that this concentration of the nervous system becomes more and more complete, as the animal acquires a higher organisation. The Crustacea have in general but very limited faculties ; and none among them present much to interest, as to their habits. The eyes are formed nearly in the same manner as in Insects ; sometimes they are simple, but in general they are compound ; and in all the most perfect Crustacea, these ORGANS OF SENSE OF CRUSTACEA. 237 organs are situated on inoveable footstalks (Fig. ."570) ; an FIG. 570.— PODOPHTHALMUS. arrangement which we do not see in any other division of Articulated animals. — In many Crustacea, there is an apparatus for hearing, situated at the base of the .external antennae, and composed of a small membrane, under which we find a sort of r vestibule filled with liquid, and inclosing the termination of a F,G.571.-Anterior part of the inferior particular nerve. This COHSti- surface of the body of a Crab (Maia) : * 01, internal antenna- ; «, external tllteS the Simplest form of an antennae; v eyes; o, organ of hear- . ,. , ing; m, feet jaws; 6, mouth ; p, base Auditory apparatus. (ANIM. of the anterior limbs; r, entrance to pHYSIOL. § 512). We kttOW the respiratory cavity ; *, sternum. e t ' nothing positive concerning the senses of Smell and Taste in these animals. 850. Most Crustacea subsist on animal substances ; but they present great differences in their regimen, some being only nour- ished upon liquid matters, whilst others feed upon solid aliment ; and we observe corresponding differences in the formation of their mouths. In masticating Crustacea there is in front of this opening a short transverse lip, followed by a pair of man- dibles, by an inferior lip, by one or two pairs of jaws properly so called, and generally by one or three pairs of auxiliary jaws, or feet-jaws, which serve principally for the prehension of food 238 MOUTH AND DIGESTIVE APPARATUS OF CRUSTACEA. (Fig. 580). In suctorial Crustacea, on the contrary, the mouth is prolonged into a sort of beak, or trunk, as we have already- seen in Insects of the same habits. In the interior of this tube, we find thin and pointed appendages, which perform the office of little lancets ; and on each side we commonly see organs, which are analogous to the auxiliary jaws of masticating Crus- tacea, but which are so formed as to serve to fix the animal on its prey. 851. The digestive canal extends from the head to the pos- terior extremity of the abdomen ; and is composed of a very short oesophagus, a large stomach (e, Fig. 572) generally armed interiorly with powerful teeth, of a small intestine, and of a rectum. In some Crustacea, the bile is secreted by biliary fo FIG. 572. — ANATOMY OF A CRAB ; the greater part of the carapace having been removed; p, portion of its lining membrane ; c, heart ; a*, ophthalmic artery ; aa, abdo. minal artery ; b, branchiae in their natural position ; b', branchias turned back to show their vessels ; fl, lower portion of the shell ; /, appendage of the foot-jaw ; e, stomach ; m, muscles of the stomach ; fo, liver. vessels, like those of Insects ; but in general there is a very voluminous liver, divided into several lobes, and composed of a CIRCULATION AND RESPIRATION OF CRUSTACEA. 239 multitude of small tubes terminating in follicles, and grouped round a ramified excretory canal, whose extremity empties itself on each side into the intestine near its commencement (fo. Fig. 572). 852. We know as yet nothing of the manner in which the chyle passes from the intestine into the circulating apparatus. The blood is colourless, or slightly tinged with blue or lilac ; and coagulates easily. This liquid is put in motion by a heart, situated on the median line of the back, and composed of but FIG. 573 — CIRCULATING APPARATUS OF LOBSTER ; a, heart ; 6 and c, arteries to the eyes and antennae ; d, hepatic artery ; e and /, arteries to thorax and abdomen ; gg, venous sinus ; A, gills ; i, branchial veins. a single cavity of variable form (Fig. 573, a). Its contraction propels the blood into the arteries, which distribute it to all parts of the body. The veins are very incomplete, and are formed chiefly by passages left between the different organs, and lined by a thin layer of areolar tissue ; they end in large cavities near the base of the legs (Fig. 574, *), from which the blood is conducted to the respiratory organs, whence it returns to the heart by very distinct canals termed branchio-cardiac vessels. 853. Crustacea are almost all essentially aquatic; their respiration is nearly always effected by gills; and when these organs are absent, their place is supplied by the skin of certain parts of the body, generally of the legs. In other respects, the arrangement of the respiratory apparatus varies consider- ably. Thus in the Crabs, Cray-fish, and all other Crustacea of analogous organisation, the gills consist of a considerable 240 RESPIRATORY APPARATUS OF CRUSTACEA. b ve number of pyramids, — each composed either of a number of minute cylinders placed like the hairs of a brush, or of little lamellae piled one on the other like the leaves of a book. — These organs are fixed by their extremities to the inferior border of the arch of the flanks (Fig. 574) ; and are inclosed in two large cavities, situated at the side of the thorax and shut in between the carapace and the arch just men- tioned, an arrangement which is not found in the other divisions of this class. The respiratory cavity communicates with the exterior FJO. 574-.— VERTICAL SECTION OF A CRUSTACEAN, SHOW- ING THK COURSE OF THE BLOOD ; c, heart ; *, venous sinus ; va, vessels conducting the venous blood to the gills ; ve, vessels which collect the aerated blood from the capillaries of the gills ; vb, branchiocardiac vessels ; /, carapace ; st, sternum. FIG. 575.— RESPIRATORY APPARATUS OF PRAWN ; a, rostrum or beak ; 6, carapace ; c, base of antennae ; d, base of abdomen ; e, base of legs ; /, gills ; g, dotted line, marking the turned-in border of the portion of the carapace that covers in the gills, which has been removed in this preparation ; h, canal for the exit of the water from the respira- tory chamber ; {, its valve ; j, its extremity. by two openings ; that which serves for the entrance of the water is situated between the base of the legs and the side of RESPIRATION OF CRUSTACEA. 241 the carapace ; the other, destined for the exit of the water, is placed at the sides of the mouth (Fig. 575). The renewal of the water in contact with the gills, is effected by the movements of a large valve, situated near this last opening, and formed by lamellated appendages of the second pair of jaws (Fig. 575, z). In other Crustacea, the Scilla for instance, the gills are formed of feathery tufts ; and instead of being inclosed in the thorax, FIG. 576.— SCILLA ; y, eyes; a, antennae; p', first pair of legs; p*, second pair of legs ; p3, three last pairs of thoracic legs : pa, abdominal pro-legs ; b, gills ; g, fin-like members. they float freely on the exterior, and are fixed to the abdominal members. In others, as the Sandhoppers, the gills are replaced by membranous vesicles fixed at the base of the legs, beneath the thorax. Lastly, in the Isopod Crustacea, the respiration is effected by means of false abdominal legs, which present a leaf-like and membranous aspect. 854. A small number of these animals are formed to exist in air ; but they constitute an exception to what has been said, relative to the difference in the structure of the breathing appa- ratus of terrestrial and aquatic animals : for, instead of being pro- vided with lungs or tracheae, they respire by gills like the former ; but these organs are placed in such a manner, as to be surrounded by that degree of moisture, which is necessary for the exercise of their functions. The Land- Crabs^ which are met with in different parts of the globe, but which chiefly abound in the Antilles, offer a remarkable example of this anomaly. Instead of living in the water like ordinary Crustacea, these animals are terrestrial ; 242 RESPIRATION AND REPRODUCTION OP CRUSTACEA. and although provided with gills, some among them are speedily suffocated by submersion in water. Indeed, their respiration i s so active, that the small quantity of oxygen dissolved in the water cannot suffice for their wants ; but in the air they find this gas in abundance ; and an arrangement similar to that which we have met with in certain Fisli (§ 558), permits them to remain out of FIG. 577.— LAVD CRAB. the water without their gills becoming so dry, as to be unfit to perform their functions. Sometimes there is, at the bottom of the respiratory cavity, a sort of basin, destined as a reservoir for the water necessary to supply the requisite moisture to the gills. In other instances, we find in the lower arch of this cavity a spongy membrane, which seems to serve the same purpose. Most of these Land-Crabs commonly inhabit moist woods, and hide themselves in holes which they dig in the soil ; but the localities which they prefer vary according to their species. Some dwell in low marshy lands, near the sea ; others in wooded hills far from the shore ; and these last at certain -periods quit their habitual dwellings for the sea. The Woodlice also are terrestrial Crustacea, whose respiration is effected by means of leaf-like plates, which are situated under the abdomen, and which, in other animals formed nearly on the same plan, fulfil the functions of gills. 855. All Crustacea are oviparous. The female is generally distinguished from the male by the more enlarged form of the abdomen ; and after having laid the eggs, she carries them for some time, suspended under that part of her body, or even inclosed in a sort of pouch, formed by the appendages to the legs. Sometimes the little ones swim about in this pouch, and remain there until they have undergone their first moult. The young do not in general undergo true metamorphoses; but sometimes they acquire, with advancing age, a larger METAMORPHOSES OF CRUSTACEA. 243 l HI. .078. EARLY FORM OF THE CRAB. number of legs ; there are some which change their form com- pletely during the first part of their life. This is the case, for example, with the common Crab, whose early condition is represented in the accompanying figure. It is remarkable, however, that in other animals of the same Order, such as the Cray-fish, the change of form is so in- considerable, as not to deserve the name of metamorphosis. Hence we perceive that the degree of this change cannot be em- ployed as a character in the subdivision of the Class, as we have seen that it may be in Insects. Of a large proportion of Crustacea, however, the early form is unknown. The metamorphoses of some of the lower tribes are even more ex- traordinary than those of the higher (Figs. 604 and 605, 609 and 610); being frequently such, as appear to remove the adult altogether from the class to which the larva evidently belongs. 856. The early condition of many of the higher Crustacea bears a strong resemblance to the permanent forms of the lower. This is in no point more remarkable, than in the character of the respiratory apparatus. Thus in the earliest period of the develop- ment of the Astacus fluviatilis, or River Cray-fish, no trace of gills can be discovered; but as the embryo within the egg approaches maturity, temporary gills are developed in the form of leaf-like expansions, occupying the situation of the extremities of the maxillary appendages, which are the first developed of all the members. These soon subdivide, and one part assumes a cylindrical form, and seems no longer to belong to the apparatus; whilst branchial filaments begin to appear on the other — which are subsequently prolonged into complete gills. During this interval, the thoracic extremities have made their appearance ; and they also become furnished with branchial appendages. At a subsequent time, a narrow groove or furrow is seen along the 244 SUBDIVISIONS OF CRUSTACEA. under edges of the thorax ; the margins of which are soon pro- longed so as to meet each other and enclose the gills, — openings being left for the entrance and exit of water. 857. The undoubted members of the class of Crustacea may be divided into five great Sections or sub-classes, including thirteen Orders; and to these we must add a sixth Section and a fourteenth Order for the curious forms already referred to (§ 822 note), which appear to unite the Crustacea with the Arachnida. A. The first Section, PODOPHTHALMA, includes all those having the eyes mounted upon foot-stalks, and moveable. They are almost always furnished with distinct branchiae ; their feet are partly formed for walking, and partly for prehension ; and the thorax is generally covered with a carapace. This Section includes the first two Orders : — I. DECAPODA, possessing five pairs of thoracic extremities, and having the gills enclosed in a special respiratory cavity. II. STOMAPODA, having the gills external, and a variable number of extremities. B. The second Section. EDRIOPHTHALMA, consists of those Crustacea whose eyes are sessile (that is, not mounted on a foot- stalk), and whose branchiae are not distinct organs, but are united with the extremities, which are commonly seven on each side. This Section contains the three succeeding Orders : — III. AMPHIPODA, in which the thoracic members are subser- vient to respiration ; and which have the abdomen well developed, and furnished with six pairs of appendages. IV. L^MODIPODA, in which the abdomen is undeveloped. V. ISOPODA, in which the abdomen is well developed, and has members, similar in form to the rest, subservient to respiration. C. The third Section, XYPHOSURA, includes a few species in which the body is incased in a strong calcareous carapace, and the tail converted into a long, sword-shaped spine. The jaws are wanting, mastication being performed by the first joints of the feet. — This Section contains only a single Order — VI. XYPHOSURA. D. The fourth Section, ENTOMOSTRACA, presents a great va- riety of form and structure, and in many cases a retrograde de- SUBDIVISIONS OF CRUSTACEA. 245 velopment takes place ; so that whilst the young exhibit all the characters of the group, the mature animal appears to be any- thing rather than a crustacean. The typical forms are covered with a shell or carapace of a horny or leathery texture, formed of two pieces; they have jointed feet, fringed with hairs; and their branchiae, when present, are attached to the feet or organs of mastication. — This Section includes six Orders, forming three well-marked groups : — a. BRANCHIOPODA, with a masticating mouth and numerous leaf-like branchiae attached to the feet, including the Orders — VII. PHTLLOPODA, with the body shell-less, or enclosed in a simple carapace, and furnished with numerous appendages. VIII. CLADOCERA, with a carapace enclosing the whole body, like a bivalve shell, and not more than six pairs of appendages. b. LOPHYROPODA, with a masticating mouth, to the organs of which the branchiae are attached ; including the Orders — IX. OSTRACODA, which has the entire body enclosed in a sort of shield resembling a bivalve shell. X. COPEPODA, in which there is no such envelope. c. PCECILOPODA, with a suctorial mouth, including the Orders — XI. SIPHONOSTOMA, in which the thorax is composed of dis- tinct rings, and bears three or four pairs of swimming feet. XII. LERN^EIDA, with the thorax undivided, and the feet rudi- mentary. E. Thejifth Section, CIRRHOPODA, includes numerous animals, which, when mature, depart widely from the type of the Class. — They are attached to marine bodies, and enclosed in a shell com- posed of several calcareous valves, from an opening in which they protrude a bundle of cirri. — They form a single Order — XIII. CIRRHOPODA. F. The sixth and last Section, ARANEIFORMIA, or the Spider- like Crustacea, includes a small number of species furnished with a suctorial mouth, and with four pairs of long jointed legs, adapted solely for walking. — They form but a single Order — XIV. ARANEIFORMIA. It is in the Order Isopoda that we find, in the equality of the segments and of their appendages, as well as in the aerial VOL. II. T 246 ORDER DECAPODA ; GENERAL CHARACTERS. | respiration of many species, the nearest approach to the class MYRIAPODA; and in some members of the Entomostracous section, we find a considerable approximation to the higher ROTIFERA. SECTION A.— PODOPHTHALMA. ORDER I.— DECAPODA. 858. In this Order we find the highest general organisation, the largest size, and the most varied habits, which we anywhere meet with among Crustacea ; it is the one most useful to Man ; and also most interesting to the Naturalist. The Lobsters, Crabs, Cray-fish, Prawns, Shrimps, — in fact, nearly all the species that are ever used as food, — belong to it. Their growth is slow ; but they ordinarily live a long time. Their habits are mostly aquatic ; but, in consequence of the manner in which their gills are inclosed, none of them are killed at once by being withdrawn from the water ; and some of them pass the greatest part of their lives in air. They are naturally voracious and carnivorous : and the first pair of legs is transformed into a pair of powerful claws, by which they seize their food and convey it to the mouth, — the claw of one side usually having a sharp edge for cutting, whilst that of the other is provided with a blunt rounded edge for bruising. The form and size of the claws, relatively to the rest of the extremities, varies greatly in the different species; thus in the Cray-fish (Fig. 579), they only seem like legs somewhat enlarged ; whilst in the Crabs (Fig. 583), they commonly seem to be distinct organs. It is in this group that we find the mouth furnished with the most complicated set of appendages ; and we may trace in these a gradual transition from the form of jaws to that of legs. This is shown in the accompanying figures, which represent the under surface of the Cray-fish, and the series of feet-jaws sepa- rately displayed. — This Order is divided into three sub-orders, ORDER DECAPODA. BRACHYOURA. 1247 according to the development of the abdomen ; thedte are : — I. The BRACHYOURA, or short-tailed Decapods, to which the name of Crabs is commonly applied ; — II. The MACROURA, or long-tailed, such as the Lobster, Cray-fah, &c. ;— and III. The Fi». 579. — CRAY-FISH ; a and b, antennae ; e, eyes ; d, organ of hearing ; e, external feet-jaws ; /, first pair of thoracic mem- bers ; g, fifth pair of thoracic members ; A, abdominal false-legs ; i, tail-fin ; ./, anus. FIG. 580. — MASTICATORY APPA RATUS, com- posed of six pairs of appendages ; a, man- dibles ; 6 and c, first and second pairs of maxillae ; d, e, /, three pairs of feet-jaws, gradually approaching the form of the or- dinary limbs. ANOMOURA, in which the condition of the abdomen is inter- mediate. Each of these sub-orders is divided into families ; but it will be sufficient here to notice their principal forms. 859. The BRACHYOURA may be considered as ranking at the head of the whole Order, in regard to the concentration and high development of their nervous, circulating, respiratory, and secreting systems. They are formed for walking rather •248 MACROUROUS DECAPODS J CRABS. than for ^wimming ; and they are consequently usually found upon the shore, or even quite inland, rather than afloat. The FIG. 581.— CARCINUS MJENAS, (Common small edible Crab); upper side, and under side of the body with the limbs cut short ; a, lateral antenna ; 6, intermediate antenna : c, eye ; d, outer foot jaw ; e, f, g, h, i, base of the five pairs of legs ; k, tail ;. I, sternum. tail or post-abdomen is shorter than the thorax, and possesses no appendages or swimmerets at its extremity ; it is folded in PIG. 582.-MAIA. a state of rest beneath tlie thorax, where it is lodged in a hollow MACROUROUS DECAPODS; — CRABS. 249 fitted to receive it ; and in the female it is furnished with four pairs of double filaments, analogous to the sub-abdominal swim- ming appendages of the long-tailed Decapods, and used for carrying the eggs. The claws, or first pair of legs, are alone furnished with pincers ; the ordinary legs having only simple pointed terminations. — In the Maia (Fig. 582) and other allied genera, the body has very much the form of that of some Spiders, and the legs are very long ; whence these Crabs are commonly termed Sea-Spiders by the fishermen. — The Cancer pagurus, or common large edible Crab, belongs to a group distinguished by the very great breadth of the carapace, which, in this species, sometimes amounts to as much as twelve inches ; it is much arched at the sides, and each border has nine festoons. This Crab is captured, by sinking pots, baskets, or nets, baited with decaying animal mat- ter, to a considerable depth along the rocky coast. Du- ring the summer months it is very abundant, especially where the water is deep; but in winter it is rarely to be found, and it is supposed to burrow in the sand, or to retire to the deeper parts of the ocean. The Carcinus Manas, or small edible Crab, is very active in its habits, run- ning with considerable speed ; it is caught, however, in large numbers, but is principally eaten by the lower classes, being less esteemed than the preceding as an article of food ; its breadth seldom exceeds three inches. There are several other species of this group, which are used as food in different parts of the world, where they take the place of the preceding. — The Podophthalmtts, which is extremely remarkable for the length of its eye-bearing foot-stalks (Fig. 570), belongs to a group of Crabs distinguished by the flattened form of the last pair of legs, which are used as oars, and enable the animal to swim with facility. 033.— CANCKK PAUUHL-S. 250 BRACHYOUROUS DECAPODS. LAND-CRABS. FIG. 584.— THELPHUSA. 860. Of the group of Brachyourous Decapods formed to live at a distance from the sea, there are many species ; some of them inhabiting fresh water, whilst others form burrows in the ground, even at a distance from water. Of the genus Thelphusa^ one fresh- water species, a native of the rivers of Southern Europe, was well known to the ancients, who often represented it upon their medals ; the Greek monks eat it uncooked, and it is a common article of food in Italy during Lent. Another species, which inhabits India, has been tnus noticed by Bishop Heber in his Journal : — " All the grass through the Dec- can generally swarms with a small Land-Crab, which burrows in the ground and runs with considerable swiftness, even when en- cumbered with a bundle of food as big as itself; this food is grass, or the green stalks of rice ; and it is amusing to see the Crabs, sitting, as it were, upright, cut their hay with their sharp pincers, and then waddling off with their sheaf to their holes, as quickly as their side-long pace will carry them." They have been found on the table-lands, at an elevation of nearly 4000 feet from the sea ; and there is reason to believe that they do not, like the West Indian Land-Crabs, perform an annual migration to the sea, for the purpose of depositing their eggs. — The Gecarcinus, or Land-Crab of the Antilles (Fig. 577), is remark- able for its nocturnal and burrowing habits, and for the migrations it executes ; when the season arrives for the depo- sition of the eggs, it moves towards the sea in large com- panies, taking the most direct line, and seldom permitting any obstacles to interrupt its progress. — Another West Indian species, the Cardisoma carnifex, inhabits the mangrove swamps, where it burrows in the soil, and feeds principally on the fruit of a kind LAND CRABS. — ANOMOUROUS DECAPODS; HERMIT CRABS. 251 of Annona. It also devours carrion ; and when burying-grounds are situated in the vicinity of its dwelling-place, will dig down into the graves to get at the bodies. This species is looked upon as a great delicacy in the West Indies. It is caught in rat-traps, and fattened, after its capture, with broken victuals. — Some of the Land-Crabs are remarkable for the inequality in the size of their claws ; the larger is used to close up the mouth of the burrows ; and it is sometimes held up in a beckoning attitude, whence these Crabs have acquired the name of Calling-Crabs. — Nearly allied to these, which are all inhabitants of tropical re- gions, are some small native species, termed Pea-Crabs, which reside, at least during a part of the year, inside various bivalve shells, such as Mussels, &c. The ancients believed that the Pea- Crab lives on the best terms with the inhabitant of the shell in which it is found ; and that it not only warns it of danger, but goes abroad to cater for it : this, however, is an absurd fiction. 861. The Decapods of the section ANOMOURA are interme- diate between the short-tailed Crabs and the Long-tailed Lob- sters and Cray-fish ; not having the abdomen reduced to the almost rudimentary state, which it presents in the former ; nor converted into a powerful organ for swimming, as in the latter (Fig. 585). There is nearly always a pair of appendages attached to its last segment ; and these have, in some instances, important uses. This section includes the Hippa (Fig. 568) and its allies, constituting the family HIPPID^E ; and also the family PAGURID^E, or Hermit- Crabs, which are very peculiar as to both their conformation and their hubits. The tail, or post-abdomen, is of large size, but its envelope is little else than a membran- ous bag, entirely unpossessed of the usual hardness of the Crus- taceous integument, and presenting no division into segments. The thorax itself is not very firm ; and it is only on the claws, which are of large size, that we find the true calcareous en- velope. For the protection of their soft tails, the Paguridce re- sort to various artificial methods. Many of them seek univalve shells, in which they take up their abodes ; attaching them- selves to their interior by a sucker, with which the tail is furnish- ed at its extremity, and also holding by the three pairs of 252 ANOMOUROUS DECAPODS; — HERMIT-CRABS. appendages, or false legs, which it bears at its hinder portion. When they are feeding or walking, the head and thorax project beyond the mouth of the shell ; but when they .are alarmed they draw themselves in, closing the mouth with one of the claws, which is much larger than the other, and holding to the interior so firmly, that they will rather be torn asunder than quit their attachment. As they increase in size, they are obliged to change their habitation for a more commodious one; and the way in which they accomplish this is very amusing. They may be not unfrequently observed crawling slowly along the line of empty shells, &c., left by the last wave; and as if unwilling to Part witn their old domicile till a new one has been obtained, they slip their tails out of the old house into the new one, again betaking themselves to the former, if the latter is not found suitable. In this manner they not unfrequently try a large number of shells, before they find one to their liking. There are several species of various sizes, which are inhabitants of our own shores ; they feed for the most part upon dead fish, and all kinds of garbage thrown upon the shore. The Birgus, an allied genus of tropical regions, has the tail somewhat more protected, but still soft ; this does not lodge in shells, but retires to rocks, or hides itself in burrows in the earth. The best-known species, Birgus latro, inhabits the Isle of France, and lives upon cocoa-nuts ; it bur- rows at the roots of the trees, and feeds upon the fruit which falls from them ; and it is even said to climb the trunk, to obtain a further supply. — In the curious genus Hypoconcha, belong- ing to the family DROMIID^;, which of all the families of Ano- moura makes the nearest approach to the preceding sub-order, the dorsal surface of the body is soft, and the animal protects it- self by attaching to this part one valve of a bivalve shell, which serves it as a sort of convex shield. The only known species, Hypoconcha sabulosa, has been found on the coasts of Cam- peachy, Cuba, and St. Domingo. MACROUROUS DECAPODS. 253 862. The MACROURA, or long- tailed Decapods, are dis- tinguished not merely by the length of the tail, but by having it terminated by a sort of fin, expanded laterally, and consisting FIQ. J8S.— PALINURU8. of five pieces (Fig. 586). This is a very powerful instrument for motion in water, serving, by its vertical strokes, to propel the animals through the liquid ; and we consequently find the Crustacea of this Section much more frequently swimming in the water than walking on its bottom or on the shore. This Section is a very extensive one, and contains the largest species of the whole class. The Lobsters, Cray-fish, Prawns, Shrimps, &c., 254 PALINURUS.— ORDER STOMAPODA. . of which the group is chiefly composed, are sufficiently well known to need no description. We may notice, however, the Palinurus, or Spiny Lobster, one of the largest animals in the class ; which was known to the Romans under the name of Locusta. This is distinguished by the very large size of its lateral antenna ; which are beset, like the body, with sharp points. The legs are all single-fingered ; not even those of the first pair being furnished with pincers. This animal frequents deep waters, especially off rocky shores ; and it only approaches the coast at the return of spring, to deposit its eggs, which are numerous, minute, and of a bright red colour. The common English species not unfrequently weighs 12 or 14 Ibs., when loaded with eggs. — The Galathea, a genus somewhat allied to the preceding, and of which two small specie% are common on our own coasts, is remarkable on account of the vast numbers in which it sometimes appears ; the Galathea gregaria having been seen by Sir Joseph Banks, during his voyage round the world, to accumulate in such multitudes, that the surface of the water appeared as if saturated with blood. ORDER II.— STOMAPODA. 863. THE name of this Order is derived from the mode in which the feet approach the mouth, in many of the animals composing it ; not only the foot-jaws, but also part of the thoracic extremities, being directed towards it (Fig. 588). The number of legs is variable ; but there are generally from twelve to sixteen, — one or more pairs of the feet-jaws of the Macrourous Decapods being here developed as true legs. The general form of the body bears considerable resemblance to that of the Cray-fish and its allies; the abdomen being much prolonged, the tail-fin much expanded laterally, and the appendages beneath the abdomen being developed and used as fin-feet. There are, however, some considerable differences in their structure ; which are quite sufficient to separate the Stomapods, as a distinct Order. The branchiae, instead of being inclosed in a cavity beneath the STOMAPODA.— MTS18, OK OPOSSUM-SHRIMP. 25D thorax, are attached to the abdominal appendages, and hang freely in the water (Fig. 576); the heart has more the form and characters of the dorsal vessel of Insects ; the integuments have little solidity, and are sometimes membranous and trans- lucent ; and the nervous system is arranged in a less concen- trated manner. — All the Stomapods are marine ; and the largest species are only found in tropical climates. As they are inhabitants of deep waters and the open sea, rather than of the shores, their habits are but little known ; but from the conform- ation of some of the Order, they may be regarded with proba- bility as very voracious. 864. As connecting this Order with the last family of the preceding, we may first notice the curious genus Mi/sis, or Opos- sum-Shrimp ; which bears, in its general form, so strong a resem- blance to the ordinary Shrimps, that it has been frequently placed with them. It is distinguished, however, from the true Decapoda, by the external position of its branchiae ; as well as by other cha- racters. In regard to the number of the feet, it holds a very interesting intermediate place between the Deca- pods and the ordinary Stomapods ; for the last pair of feet-jaws is developed into true legs, making their number twelve in all; and the other two pairs have much more the form of ordinary legs, than in the Decapods. Each of the legs has a lateral ap- pendage, which is so much developed as to appear like a second limb ; and thus reckoning in the feet-jaws, which also possess similar appendages, we may say that the Mysis has no fewer than 32 legs. The common name of this curious little animal is derived from the peculiar conformation, which enables it to afford a special protection to the eggs. The female has a large concave scale, attached to the inner division of each of the posterior legs ; and these, overlapping one another, form a pouch, which is capable ot being considerably distended. Into this pouch the eggs are re- ceived, when they quit the ovarium ; and here they continue until :256 ORDER STOMAPODA. — SQUILLA MANTIS. the young are so nearly developed, that they present a very close resemblance to the parent. The parent then opens the valves of the pouch, and sets free tn"e whole brood at once into the surround- ing element ; and these usually seem to remain associated with the community from which they sprang. Although sparingly distributed in the seas of Europe, these little animals inhabit some parts of the Arctic ocean in amazing numbers ; constituting the principal food of the prodigious shoals of Salmon, which resort thither in the months of July and August, and upon which the inhabitants of Boothia depend in great degree for their winter store of provisions ; and serving also as one of the chief articles, on which the Whalebone Whale is supported. 865. The Squilla, which is sometimes termed " Sea Mantis," from the resemblance of its powerful claws to those of that Insect (§ 728), may be regarded as the type of the Order. Its carapace is small, and only covers the anterior half of the thorax ; — the posterior being formed of rings like those of the abdomen. FIG. 588.— SauiLLA MANTIS. The members, which, in their position, correspond with the external feet-jaws of Decapods (Fig. 588, a), are here developed into enormous claws, terminating in a sharp hook ; in the typical species, Squilla mantis, the last joint or finger is furnished with six sharp projecting spines ; and the preceding joint, or hand, is furn- ished with three sharp spines, and is hollowed at its edge into a groove, into which the finger shuts, in such a manner as to render this claw a most efficient instrument of prehension. The other foot-jaws, and the three first pairs of thoracic members (b\ share in this conformation ; being furnished with a sharp move-able finger, and a hand armed with spines, against which the finger closes ; ORDER 8TOMAPODA ;— PHYLLOSOMA, OR GLASS-CRAB. 25? and these are directed towards the mouth, in such a manner as to hold the prey again'st it, in the most efficient manner. The three posterior pairs of legs, which are attached to the annulated (or ringed) portion of the thorax (c), are furnished with a brush instead of a hook at their extremities, and more resemble the ab- dominal swimming legs. The tail is expanded into a broad fin. Thus we see that the locomotive apparatus of this animal is partly adapted for prehension, and partly for natation (or swim- ming), and not at all for walking. This species is probably the largest of the Order ; its length being about seven inches. It is common in the Mediterranean. 866. To this Order also belongs a very curious genus, the Phyl- losoma, or Glass-Crab. Its scientific name, which means leaf- bodied, as well as its common designation, refer to the remarkable peculiarity of structure by which it is distinguished j the whole body being flattened like a leaf, and almost as transparent as glass. It is composed of a large oval plate, which represents the head, and bears the two eyes, mounted on long footstalks, at its anterior extremity ; of a second plate, in part covered by the preceding, and bearing the thoracic legs; and of an abdomen which is always short, and sometimes undeveloped. The legs, six in number, are very long and slender ; they are bifid, like those of the Mysis ; and are adapted for swimming only. These curi- ous creatures are inhabitants of the tropical parts of the Atlantic and Eastern Oceans. 867. It is scarcely possible to avoid being struck by the analogy presented by this Order to the Orthoptera among Insects. The resemblance of the Squilla to the Mantis has already been noticed ; and the correspondence of the Phyllosoma to the leaf-like species of the same order (§ 729), is scarcely less remarkable. We may also point out the many resemblances between the Decapod Crus- tacea and the Coleopterous Insects. They occupy a corresponding position, in being at the head of the mandibulate series of their re- spective classes ; they are both also pre-eminent in regard to the hard- ness of their integuments ; and in bojfch there is an adaptation of the extremities for walking, rather than for swimming or flying — which are actions analogous to each other (ANIM. PHYSIOL., § 663). SECTION B,— EDRIOPHTHALMA. ORDER III.— AMPHIPODA. 868. Passing on to the group of EDRIOPHTHALMA, — which is distinguished by the absence of peduncles supporting the eyes, and by the union of the respiratory organs with the locomotive members, — we have first to notice the Order AMPHIPODA, in which the abdomen is well developed, but the respiratory organs are connected with Fro. 589.— GAMMARUS PULXX. the thoracic limbs only. These organs consist of membranous vesicles, at- tached to the base of the legs, of which some traces present them- selves in the preceding Order ; the continual renewal of the water in contact with them is accomplished by the constant movements of the first three pairs of abdominal pro-legs. The thoracic legs are fourteen in number, consisting of the ten which are characteristic of the Decapods, with the addition of two pairs of feet-jaws, — only one pair of these last organs being here left in its original form. The legs are partly directed forwards, and partly backwards, from which the name of the Order is derived. The abdomen is much developed, and is composed of seven segments, — the last, however, being a mere rudiment ; the appendages of the three preceding divisions are often united into a sort of bundle, constituting an organ whieh is of great service in leaping. These Crustacea are all of small size ; but they frequently present themselves in very large numbers. Some of them are inhabitants of the sea and shores, whilst others are abundant in our streams. The greater number of them are very agile leapers. 869. The common Talitrus locusta, or Sand-hopper (Fig. 564), AMPHIPODA; — SAND-HOPPER, &c. 259 is a very characteristic example of this Order. It is extremely- abundant on our shores ; and may often be seen in vast numbers on the sands, especially when the sun is shining upon them and the tide is retreating. The whole surface of the sand, or rather the air for a few inches above it, appears as if alive with them ; for they are incessantly leaping to an elevation, which is, for their minute size, very considerable, as if they were in the height of enjoyment. They burrow in the sand ; and seldom enter the water. Their food probably consists of the minuter animals, and of the decomposing animal and vegetable remains, which are left in the sand by the sea. The Gammarus pulex (Fig. 589), which is nearly allied to the preceding in structure and in its leaping powers, is an inhabitant of fresh water brooks; being especially abundant in those, in which there is an accu- mulation of decaying vegetable matter. The Corypkmm is remarkable for its very long antennae, and for its pre- daceous habits. It is very abundant on the coast of La Rochelle, where it forms extensive burrows in the Fio. 590. — COR YpnruM LONOICOKNR ; a, terminal •, 1 •, . ., segment of the tail. sand,— only making its ap- pearance, however, at the beginning of May. It keeps up a continual war with the Anne- lida, which inhabit the same neighbourhood ; and also attacks Mollusca and even Fishes, as well as dead animal matter. Scarcely anything is more curious, than to observe these creatures at the rising of the tide assembled in myriads, moving about in all directions, beating the mud with their arm-like antennae, and mixing it with water in order to discover their prey. If they meet with Annelids even ten or twenty times their size, they unite together to attack and devour them ; and the carnage does not cease, until the whole of the mud has been turned over and examined. It is said that they sever the byssus, by which the Mussels are fixed (§ 1030) ; so as to cause them to fall, and thus to enable them to be more readily attacked. They are in their turn devoured by Fishes and by many Shore-Birds. The Crustacea 260 ORDER L.EMQD1PODA ; — CAPRELLA. of a portion of tins Order are parasitic in their habits ; attaching themselves to the bodies of Fishes ; and having the mouth more adapted for suction. ORDER IV.—L^EMODIPODA. 870. The Crustacea of this Order resemble the preceding in the conformation of the respiratory organs ; but differ from all the other Edriophthalma, in the want of development of the abdomen. The number of legs varies considerably in the different species. The body is composed (with the head) of eight or nine segments, of which seven may be furnished with members ; but not unfrequently some of the appendages are undeveloped. This Order is divided into two Sections, according to the form of the body; the Filifor- mia, having the body long and thread-like, and the legs also long and slender (Fig. 591); Whilst in the Ovalia, FJQ< SSI.-CAPRBLLA PHASMA. the body is shorter and broader, and the legs shorter and stouter (Fig. 592). Of the former group, the Caprella phasma is a characteristic exam- ple; it is found among marine plants, creeping along in the same manner as the Geometer, or Looper- Caterpillars (§ 768) ; often bending itself back with great rapidity, and applying its antennas to various parts of the body. It has five pairs of legs, of which the second is the largest ; these are not disposed, however, in a regular, but in an interrupted series, the second and third segments of the thorax having only the respiratory vesicles. In an allied genus, there are also ten legs, disposed in a con- tinuous series ; and in another, all the fourteen are developed. CYAMUS. ORDER ISOPODA. 261 The Cyamus and its allies, belonging to the second division of the Order, appear to be mostly parasitic in their habits. The Cyamus, commonly termed the Whale-Louse, attaches itself, by means of its strong claws, to the surface of the body of the "Whale; which is sometimes so completely covered by these parasites, that the individuals thus infested may be easily recognised at a considerable distance by their white colour. When the parasites are removed, the skin of the Whale is found to be deprived of its epidermis. ORDER V.— ISOPODA. 871. These Crustacea bear a general resemblance to the Amphipoda ; but their bodies are flattened horizontally, instead of being compressed vertically, and the abdomen is not terminated either by appendages adapted for leaping, nor by an expanded fin for swimming, as in that group. The thorax nearly always consists of seven segments, and is furnished with seven pairs of appendages adapted for walking (Fig. 565) ; but the respiratory organs are not attached to them, but are developed as expansions of the extremities of the pro-legs, which are attached to the abdominal segments. These organs, which have usually an oval form and a membranous texture, are sometimes suspended freely beneath the abdomen ; but they are occasionally covered in by little scales, which fold over and protect them. The females usually have large plates attached to the base of the thoracic legs, which form, by their meeting, a pouch in which the eggs and young are matured ; others have a membranous bag in this situation. The newly-hatched young have only six thoracic segments and six pairs of legs, — acquiring an additional segment and pair of legs at the time of their first moult. 872. Of this Order, the principal part is aquatic; but one group is terrestrial. Many of the former are parasitic upon other animals, — very frequently upon larger Crustacea; this is the case with the Bopyrus, which is parasitic upon the common Prawn, affixing itself beneath -the carapace, upon the branchiae, VOL. ii. u 262 ORDER ISOPODA ,* LIMNORIA, WOOD-LOUSE. and producing an evident swelling externally. Between eight and nine hundred young ones have been observed beneath the body of a single female ; and the parent has the instinct to set them free in situations frequented by the Prawns. — Of those marine Isopods which are not parasitic, the most worthy of notice is the Limnoria terelrans ; which, although not more than a sixth of an inch in length, is, through its boring habits, and its powers of multiplication, exceedingly destructive. It pierces timber in different directions with astonishing rapidity, appa- rently for the purpose of feeding upon it, as in its stomach are found minute particles of the wood. It is found in different parts of the British Ocean, attacking wooden piles, immersed in water, in our dock-yards, bridges, flood-gates, chain-piers, &o. ; and perforating them in the most alarming manner. 873. It is in the terrestrial species, that we find the most remarkable provision for the inclosure of the respiratory organs ; these being completely folded over, by plates developed from the abdominal members ; and the anterior plates being perforated with a row of small holes, through which the air gains access to the gills within. Like the Land Crabs, these terrestrial Iso- pods (of which the common Wood-louse is a very familiar example), for the most part frequent damp situations ; inhabiting dark and con- cealed places, such as cellars, caves, holes in walls, the un- der-side of stones, &c. They feed upon decaying animal and vegetable matter, and come forth from their retreat in damp weather. They crawl slowly, except when alarmed ; and they have the power of rolling themselves into a ball, so as to expose on the outside nothing but the plates of the back, and to conceal the appendages of the underside of the body. FIG. 594.— ARMADILLO PUSTULATUS. FIG. 593 — ANILOCRUS. ORDER ISOPODA ;— TRILOBITES. 263 874. This is probably the situation, in which we are to place the remarkable fossils known under the name of Trilobites, from FIG. 595. — CALYMENE FIG. 59C.— A, ASAPHUS EXPANSUS. B, THE SAME BLUUENBACHII. EOLLED UP. the three lobes into which the body is divided lengthways (Fig. 595). These are found in the very earliest of the formations that contain fossils at all; and they appear to have ceased to exist before the creation of Mammalia. They resemble the Isopoda in the equality of their segments, as well as in the tri-lobed division of the body, which is presented by some of the recent species of that Order ; and also in their tendency to roll themselves into a ball (Fig. 596). Their exact situation, however, cannot be known, until some information has been gained in regard to their ex- tremities, of which we know as yet next to nothing. The slight traces of these organs which have been discovered seem to in- dicate that they bore some resemblance to the feet of the Phyllo- poda, and it is probably as an Order intermediate between the latter and the Isopoda that we must regard the Trilobites. — They bear no inconsiderable resemblance externally to the Chitons among Mollusca (Fig. 673) ; and could probably, like them, draw the border of the shell completely down to the surface on which they were adherent. Their Articulated character, however, is fully evidenced by the nature of their eyes, which have the com- pound structure peculiar to that Sub-Kingdom. This has been so perfectly preserved in many specimens, that the facets may be counted with the aid of a magnifying-glass ; and as many as four hundred have been found to exist in a single specimen. 264 SECTION C. ORDER VI.— XYPHOSURA. 875. Although this group only contains a single genus, the Limulus, or King-crab, yet the structure of this departs so widely from that of all the Crustacea we have hitherto con- sidered, that it cannot be referred to the same Order, or even the same Sub-Class, with any of them. The Limuli, — which are Crustacea of considerable size, sometimes attaining the length of two feet, — have their bodies divided into two parts ; of which the anterior, covered by a large semicircular shield (c, Fig. 598), bears the eyes, the antennae, and six pairs of legs, which sur- TIG. 597.— LIMULUS. FIG. 598.— UND] R SURFACE OF LlMULUS. round the mouth (£), and are used both for walking and for mastication ; whilst the posterior portion of the body, wliich is ORDER XYPHOSURA ;— LIMULUS OR KING-CRAB. 265 covered by another shield of a somewhat hexagonal shape, bears on its under surface five pairs of swimming legs, of which the last is furnished with gills; and this hexagonal shield termin- ates in a long pointed process (q). Now when we compare the appendages to the head and body of these animals, with those of ordinary Crustacea, it is evident that the first pair of the legs sur- rounding the mouth of the Limulus represents their mandibles ; that the second and third pairs represent their maxillae; the three following pairs of legs their feet-jaws ; and the five pairs of swimming-members, abdominal fin-feet, — the true thoracic legs being altogether absent. Besides the pair of compound eyes, characteristic of the Crustacea in general, the Limuli have a pair of small simple eyes, placed' anteriorly, near the central line. — The Limuli are confined to the shores of tropical Asia, the Asia- tic Archipelago, and tropical America. As the best-known species comes from the Molucca Islands, they are sometimes termed Molucca Crabs. Of their habits very little has been ascertained. They appear to prefer the neighbourhood of sandy shores, and it is said that when kept from the water, they bury themselves in the sand, in order to avoid the violent heat of the sun, which causes them speedily to perish. They feed upon animal flesh. The long process of the posterior shield is not developed in the young animal ; which also wants the posterior branchial mem- bers. This process is used by some of the Malays as a point for their arrows; the wounds it makes being dangerous, like those made by the spines of many Fishes, on account of their jagged character. On the coast of America, where the Limulus is known as the Casserole Fish, the shell is employed as a ladle for water. —Fossil remains of this genus are not uncommon in the Second- ary and Tertiary strata ; and it may be further remarked that, in several particulars, the Trilobites may be regarded as having been probably analogous to it. 266 SECTION D.— ENTOMOSTRACA. ORDER VII.— PHYLLOPODA. 876. We are now arrived at the fourth Section of the class,— that of ENTOMOSTRACA j in which the union between the legs and respiratory organs, which we have seen to be gradually taking place in the preceding Orders, becomes more complete, — there being now no distinct gills, and the anterior legs being converted into respiratory organs, by an expansion of their sur- face. In the greater part of this and the succeeding groups, the body is inclosed in a sort of horny shell ; which sometimes appears composed of but a single piece, and in other instances is formed like the shell of a bivalve Mollusk : — hence they are commonly known as Entomostracous Crustacea (this term meaning, inclosed in a shell). The eyes are generally placed near each other ; and are sometimes so close, as to run together (so to speak) into one mass. The foot-jaws are all converted into true legs, being, like them, adapted for swimming ; and even the antennae sometimes become locomotive organs. The number of legs varies greatly ; reaching in some species to above a hundred ; but being commonly much less. All these animals are aquatic, and most of ihem inhabit fresh water. They are for the most part extremely active in their habits ; and are all of small size, some of them being even of microscopic minute- FIQ 599.— CYCLOPS ness< This active locomotion is doubtless in VULGARIS, magnified, part connected with the act of respiration, and serves to produce a constant interchange in the water in contact with the surface of the body, and especially PHTLLOPODA ;— LIMNADIA ; APUS. 267 with the branchial expansions of the legs. Even when the animals are at rest, these last organs are seen to be in rapid motion. The eggs are arranged in a mass in a cavity beneath the back of the shell, or are inclosed in a common envelope, and carried in one or two bunches or masses at the base of the tail (Fig. 599 j. 877. The Order PIIYLLOPODA includes those Entomostraca, whose body, sometimes naked or shell-less, and sometimes in- closed in a shield-like carapace or in a bivalve shell, is divided into a great number of segments, nearly all of which are furnished with leaf-like appendages, or gill-feet. They vary considerably in their conformation ; some of them being provided with a certain number of simple swimming feet, placed behind the gill-feet ; but of the latter there are always at least eight pairs, and sometimes their number amounts to sixty pairs. The first division of the Order includes those, which have the body protected by a horny shell. This is the case with the Limnadia (Fig. 600), which has a bivalve shell, and bears a considerable FIG. 600.— LIMNADIA. FIG. 601.— APTJS MONTAGUI. resemblance to the Daphnia (§ 879), except in the form and number of the feet; and in the Apus (Fig. 601), which has a simple shield-like shell, and in which the feet are very numerous, but all except the anterior ones are extremely small. These last are extremely remarkable for the immense number of pieces, cal- culated at about two millions, of which their bodies are composed ; and also for the power which their eggs possess, of retaining their vitality for several years, when the waters in which they are deposited have been dried up. They inhabit lakes, pools, and ditches, and are often found in vast numbers, especially in the 268 PHYLLOPODA ;— BRINE-SHRIMP. spring and beginning of the summer. They are sometimes raised into the air by whirlwinds, and scattered again like rain. Their eggs are of a red colour, and fall to the bottom of the water, when set free from the egg-cases which the parent bears near its tail. When first hatched, the young differ considerably from their pa- rents, having but one eye, four legs, no tail, and the shell cover- ing only the front half of the body. These Crustacea, which are amongst the largest members of this section, appear to feed chiefly upon the smaller Entomostraca, and are in their turn attacked by Frogs. They swim well on the back, and burrow in the sand, elevating their tails in the water. 878. In the species included in the second division of the Order, there is neither bivalve shell, nor any trace of a shield- like carapace ; but the body is entirely soft. It is usually much prolonged, and composed of a large number of segments ; but the branchial appendages or gill-feet do not exceed eleven pairs. To this group belongs the curious Artemia salina, or Brine-shrimp ; a small Crus- tacean, about half an inch in length, commonly found in the salt-pans at Lymington, when the evaporation of the water is so far advanced that the fluid contains a quarter of a pound of salt in the pint. The accompanying figures repre- sent the progressive stages of its development. "Nature having constructed it with members solely adapted for swimming, it seems to be in perpetual quest of prey, gliding with an almost even motion through the water, and moving with equal indif- ference on the back, belly, and sides ; the shape of the animal, the undulating movements of its fins, and the glossy appearance of its coat, render it an object of a very interesting description." The reservoirs in -ARTEMIA SAUNA, in different stages. FIG. 603 — CHIROCEPHALTJS DIOPHANX.S. CHIROCEPHALUS.— ORDER CLADOCERA. 269 which they are chiefly found, are called " clearers," as the liquid becomes clear in them ; and this is attributed by the workmen to the rapid motion of the feet of these little creatures ; and so firmly are they persuaded of this, that, according to Mr. Rackett, they will transport a few brine-worms, as they call them, from one saltern in which these animals are abundant, to another in which they do not make their appearance. — Nearly allied to this is the Chi- rocephalus ; of which the several species are found, often in great numbers, in small pools, especially after heavy rain ; sometimes even in those which are left on the uneven surfaces of stones, — the eggs, which are inclosed in a strong shell, seeming to have been transported by the wind. The Chirocephali generally swim on their backs ; and their short lamellar feet, which are unfit for walking, are then kept in an undulatory motion, that sends forward a current of water, along a channel hollowed in the lower side of the body, to the mouth, and thus supplies the animal with food. At other times, they swim more forcibly, by alternate lateral strokes of the tail upon the water. The British species (Fig. 603) measures more than an inch in length, and is a very beautiful creature. ORDER VIII.— CLADOCERA. 879. The Order CLADOCERA consists of those minute Crus- tacea answering to the foregoing description, which have the body inclosed in a bivalve shell. These belong, for the most part, to as wel1 as from the absence of a respiratory apparatus, the circulating system may be regarded either as incomplete, or as altogether wanting, — the respiration being provided for, as in the lower tribes of Crustacea, by the exposure of the fluids of the body to the sur- rounding medium. Krohn, however, has lately stated that these animals possess a dorsal vessel, similar in structure to that of the Insects and Arachnida ; and they are said to possess traces of a ARANEIFORM CRUSTACEA.— PYCNOGONIDJE. 287 nervous system, and four eyes placed upon a tubercle on the an- terior segment. Their minuteness renders it difficult to as- certain many^ points of their structure ; and much is still to be learned respecting them. Various species exist on our own coasts. Their motions are remarkably slow, and appa- rently difficult; and it is obvious from this circumstance, as well as from the conformation of the mouth, that their prey must consist of either dead animal matter, or of living animals as defenceless as themselves. The body consists of a sort of cephalothorax, composed of four segments, each bear- ing a pair of legs ; it is terminated in front by a conical rostrum, often ac- companied by a pair of pal- piform organs, and behind by a minute abdomen. The females are distinguished by the possession of a pair of spurious legs (Fig. 619), placed in front of the rest, and appropriated to the purpose of holding and carrying the eggs. These |re collected into globular masses, enveloped with a thin skin or membrane, each mass being firmly adherent to the limb. There are several of these masses in most species of the tribe ; but in Pycnogonum itself, the eggs form a single broad square membrane laid under the body. Of the development of these curious animals we know scarcely anything, except that the young on leaving the egg are only furnished with four short legs beset with long filaments, so that they must undergo considerable changes' before reaching maturity. With regard to their habits, our information is equally deficient. FIG. 619.— NTMPHON GROSSIPES, and under side of its Beak. GEOGRAPHICAL DISTRIBUTION OF CRUSTACEA. The extensive study of this large and important class, by M. Milne-Edwards, has enabled him to arrive at some very in- teresting conclusions in regard to its Geographical Distribution. An outline of these will be here introduced, because they would probably serve, with so"me modifications, to represent the general facts relating to the distribution of other Classes. 900. It has been pointed out, in the preceding sketch of the principal forms of the Crustacea, that different species have different localities, or residences assigned to them (as it were), on the surface of the globe. We have seen that some are exclu- sively confined to fresh water, — that others are inhabitants of the brackish water of estuaries, — that others take up their abode on the shore, where they are periodically covered and left dry by the tide,— that others frequent the shallow waters in the neigh- bourhood of the shore,— that others are found near the bottom of the deeper waters, at no great distance from land, — that others, again, roam freely through the open sea, — and finally, that others are only to be met with on the- dry land, at a considerable dis- tance from the shore. Thus we see that each species has an appropriate kind of residence, for which it is peculiarly adapted by its organisation and habits ; but it may be further stated, that each species has an appropriate place of residence, which is very much determined by the temperature of the region. It is true that there are many species very extensively distributed ; but this results from their being adapted, by some peculiarities of structure and habit, which we cannot detect, to sustain life under a considerable variety of external conditions (§ 13). The extent to which even these species are distributed, however, will GEOGRAPHICAL DISTRIBUTION OF CRUSTACEA. 289 depend, in great part, upon the locomotive powers with which they are endowed, either in their adult or their young states ; and also (in regard, at least, to all but the freely-swimming marine species) to the continuity of a line of coast, from one point to any- other, along which their migrations may be effected. The existence of constant or periodical currents, too, — such as the Gulf Stream of Mexico, — will often affect the distribution of species ; thus it is probably to this cause, that we are to attribute the presence of some American Crustacea on the shores of the Canary Islands. 901. The following are the general principles arrived at by M. Milne-Edwards in regard to the influence of Temperature on the Geographical Distribution of Crustacea. I. The different forms and modes of organisation of these animals manifest themselves more, in proportion as ice pass from the Polar Seas towards the Equator. — Thus, on the coasts of Norway, where there is frequently a vast multiplication of individuals of the same species, the number of species is very small ; but the latter increase rapidly as we go southwards. Thus the number of species of Crustacea of the first two Orders, known to exist on the coast of Norway and the neighbouring seas, is only sixteen ; but eighty-two are known to be inhabitants of the western shores of Britain, France, Spain, and Portugal; one hundred and fourteen are known in the Mediterranean Sea; and two hundred and two in the Indian Ocean. A similar increase may be observed in fol- lowing the coast of the New World, from Greenland to the Caribbean Sea ; the number of species of Decapods in the former region being only twelve, whilst in the latter it is seventy-one. II. The differences of form and organisation are not only more numerous and more characteristic in the warm than in the cold regions of the globe ; they are also more important. — The number of natural groups, which we find represented in the Polar and Tem- perate Regions, is much smaller than that of which we find types or examples in Tropical Seas. In fact, nearly all the principal forms, which are met with in colder regions, also present them- selves in warm ; but a very large proportion of the latter have no representatives among the former. Thus, of the three primary groups, into which the Class is at first subdivided, the Xypho- 290 GEOGRAPHICAL DISTRIBUTION OF CRUSTACEA. sura are altogether wanting beyond the forty-fourth degree of latitude. Again, the Brachyourous and Anomourous Decapods appear to be altogether excluded from some of the most northern regions that have been explored. Of the family of SquillidaB (§ 791), so highly characteristic of the Order Stomapoda, it is rare to meet with any members, north of the forty-fifth degree of latitude. And the curious group of Phyllopoda is restricted within a still nearer neighbourhood of the Tropical Region. III. Not only are those Crustacea, which are most elevated in the scale, deficient in the Polar Regions ; but their relative num- ber increases rapidly as we pass from the Pole towards the Equator. Thus the Brachyoura, which must be considered as the most elevated of the whole series, are totally absent, as we have just seen, in some parts of the arctic region ; and we find their place taken by the far less complete Edriophthalma, with a small num- ber of Anomourous and Macrourous Decapods. In the Mediterra- nean, however, the Decapods surpass the Edriophthalma in regard to the number of species ; and the Brachyourous division predomi- nates over the Macrourous, in the proportion of two to one. And in the East and West Indies, the short-tailed are to the long-tailed Decapods, as three, four, or even five, to one. — Again, the Land-Crabs, which are probably to be regarded as taking the highest rank among the Brachyoura, are only to be met with between the tropics. And of the fiuviatile Decapods (those which inhabit rivers, brooks, and lakes), a large proportion belong in tropical regions to the elevated type of the Brachy- oura ; whilst all those found in the temperate and arctic zones belong to the Macrourous division. IV. When we compare together the Crustacea of different parts of the world, we observe that the average size of these animals is considerably greater in tropical regions, than in the temperate or frigid climes. The largest species of the arctic and antarctic seas, are far smaller than those of the tropical ocean ; and they bear a much smaller proportion to the whole number. Further, in almost every group, we find that the largest species belong to the equatorial regions ; and that those which represent them (or take their place, as it were) in temperate regions, are of smaller dimensions. GEOGRAPHICAL DISTRIBUTION OF CRUSTACEA. 291 V. It is where the species are most numerous and varied, and where they attain the greatest size, — in other words, where the. temperature is most elevated, — that the peculiarities of structure, which characterize the several groups, are most strongly manifested. Thus the transverse development of the cephalo-thorax, which is so remarkable in the Brachyourous Decapods (the breadth of the carapace of the typical Crabs being much greater than its length from back to front), is carried to its greatest extent in certain Crustacea of the Equatorial region; and the same might be stated of the characteristic peculiarities of most other natural groups. Further, it is in this region that we find the greater part of those anomalous forms, which depart most widely from the general structure of the Class. VI. Lastly, there is a remarkable coincidence between the temperature of different regions, and the prevalence of certain forms of Crustaceous animals. * Thus there are few genera to be met with in the West Indian seas, which are not represented in the East Indian, — the species, however, being usually different. The same may be said of the genera inhabiting the temperate regions of the globe ; — similar generic forms being usually met with in the corresponding parts of the Old and New World, and of the Northern and Southern Hemispheres, although the species are almost invariably different. CHAPTER XIII. OF THE VERMIFORM CLASSES. 902. We are now arrived at the lower division of the Arti- culated Sub-kingdom, in which there is an absence of articulated members, and a general inferiority in the structure of the animals composing it ; so that, as we descend, we lose one after another of those characters, by which this group is distinguished. Nevertheless, the lateral symmetry (§ 47) of the body is almost uniformly preserved ; and it is only in the very lowest that we meet with any approach to the circular arrangement of the parts of the body, which is characteristic of the Radiata. The Ner- vous System cannot be traced in the simplest animals of this division ; but wherever it can be detected, it presents the same essential characters as in the higher classes, — consisting of a double cord running along the ventral surface from one extremity of the body to the other, and studded with ganglia at intervals. These ganglia are smaller, in proportion as they are more nume- rous ; and their size diminishes, too, with the diminution of the locomotive powers of the animal. The cephalic ganglia, or those which are placed at the anterior extremity of the body, above the oesophagus, are usually larger than the rest ; especially when they are connected with organs of special sense, such as eyes and antennas. But as we descend through this series, we find the eyes disappearing, and then the antennae ; so that the head is only marked by its being the situation of the mouth ; and the cephalic ganglia are then scarcely to be distinguished from the rest. 903. "!The body of these animals is generally long, slender, and more or less cylindrical ; it is frequently divided into dis- tinct segments ; but these are only marked externally by a folding or wrinkling of the integuments ; and there does not GENERAL CHARACTERS OF VERMIFORM ARTICULATA. 29 exist any proper tegumentary skeleton or hard envelope, as in most of the higher classes of Articulata. In the lowest mem- FIG. G2?.— LEC-CH. bers of the class, indeed, we cannot even trace an integument distinct from the contained tissues; all being alike soft, and some- times almost jelly-like. Even here, however, the division into segments is most distinctly marked, by the repetition, in each segment, of nearly all the organs of the body ; so that the animal is much more capable of sustaining severe injuries, than is the case in the higher classes ; and it has also greater power of repairing them, new segments being developed to replace those which had been lost. The greater number of the Vermi- form or "Worm-like Articulata are aquatic in their habits, livirrg either in water or in moist situations ; and as a general rule, their respiration is performed either by gills, or by the general surface of the body. They have usually a distinct circulating appara- tus ; which serves not only to convey the nutritious fluid through the several tissues, to whose growth it is to contribute, but also to carry it to the organs in which it is to undergo aeration. This apparatus consists, as in Insects, of a dorsal vessel, running along the greater part of the body, and contracting from behind forwards, so as to expel the blood through the branches which proceed from its anterior extremity ; the fluid then flows back- wards through the body, affording nutriment to its several parts in its course ; and it is then made to flow over the walls of the alimentary canal, so as to take up from its cavity any new materials, which may have been prepared for it. The pro- visions for carrying it through the respiratory organs vary greatly, in proportion to the variety jn the arrangement of the respiratory organs themselves, which we shall see to be as great, as it is in the Mollusca : butfthere is not unfrequently a distinct contractile cavity, or respiratory heart (ANIM. PHYSIOL. § 281), for propelling the blood through every pair of gills, as in the VOL. II. T 294 VERMIFORM ARTICULATA. CLASS OP ANNELIDA. Crustacea (§ 852). In the lowest Articulata, however, no dorsal vessel, or impelling organ of any kind, can be discovered ; and the circulating system consists merely of a network of capillary vessels, occasionally merging into larger trunks ; the blood being propelled through it by the continual movements of the body itself, which act upon it in somewhat the same manner that our own changes in position do upon our venous circulation (ANIM. PHYSIOL. § 279). 904. This group may be regarded as especially represented by the class ANNELIDA ; which contains, with the Leech and Earthworm, a great number of marine animals less gene- rally known. In the ENTOZOA, we find the characters of the Articulated series in their lowest state of development. And in the ROTIFERA, we meet with peculiarities of form so great, that the affinity of the minute animals it contains to the preceding classes, is by no means apparent without a careful examination. CLASS OF ANNELIDA. 905. The Annelida may be characterised as possessing an elongated body, marked by transverse lines that divide it into numerous segments : and usually furnished with a series of loco- motive appendages in the form of bristles, sometimes implanted on fleshy tubercles ; but not with articulated members. They have a complete apparatus for circulation and respiration ; and FIG. 621 — NEREIS. the ventral chain of nervous ganglia may always be distinguished. — Of the appendages which often combine the functions of loco- LOCOMOTIVE APPEN] OF ANNELIDA. 293 motion and respiration, there are frequently two pairs in each segment ; one belonging to its upper or dorsal portion, and the other to its lower or ventral (Fig. 388) : but in other in- stances the two appendages on the same side are united (Fig. 628). We usually then find, in the marine Annelida, that the ventral portion is chiefly devoted to locomotion ; and the dorsal to respiration. Thus, in the Eunice, we find, at the under part, a fleshy tubercle (t), furnished with a tuft of bristles, and below it a rudimentary cirrkus, or tendril-like organ (t) ; whilst the upper part of the appendage is formed by a branchial tuft (6), and by a long slender cirrhus (c). This last sometimes exhibits a trace of articulation, as in the Syttis (Fig. 623, a). In other cases, however, these appen- FIG. 622.— GIT.L- TUFT OP EUNICE. FIG. 623. — SYLLIS MONILARIS, with one of its locomotive organs and setigerous appendage attached thereto. dages are only represented by a few short stiff hairs, as in the Earthworm ; and in other instances, as the Leech> there is no trace of any members or appendages to the body. The bristly tufts of the Nereidans and their allies are useful to them in various ways ; they serve them in part as instruments of attack and defence, the bristles being usually sharp, and sometimes barbed at their extremities, so as to attach themselves with force to soft substances ; they assist, also, in their movements over solid surfaces, taking hold, as it were, of the rock on which the animal is crawling, so that the hinder part of the body is pre- vented from slipping back, when the anterior part is pushed forwards ; and they also aid in its movements through the 230 GENERAL CHARACTERS OP ANNELIDA. water, serving in some degree as oars by which it is propelled. In some instances, indeed, we find the tufts replaced by flattened plates, which are specially adapted for this last purpose. Where there are no locomotive appendages, the extremities of the body are usually furnished with suckers, which give important assist- ance in locomotion, — as in the well-known Leech. But in one tribe of this class, the animal, in its adult form at least, enjoys very little power of locomotion, being confined within a shell, which it constructs for itself, and which is attached to some solid support. 906. The first segment, which constitutes the head, is usually provided with one or more pairs of imperfectly-formed eyes ; and also with several appendages analogous to the cirrhi of the other segments, which are considered as antennae or tentacular cirrhi. The mouth, which is situated on the lower side of the head, ia constructed on a very different plan in the several divi- sions of the class : being sometimes furnished with one, two, or three pairs of hard horny jaws, with toothed or pointed edges ; sometimes having a sort of trunk, which can be pushed out or tr drawn in (Fig. 624), and which bears a pair of small tooth-like jaws at its extremity ; and some- Mines being situated in the centre of a flattened sucker, and armed with an apparatus of little saws, FIG 624 — HEAD AND TRUNK OF GLV- ,, T •> /-.-,. /?0i \ c, anterior portion of the as m the Leech (Flg- 631)« body ; t , head ; tr, trunk ; 6, opening alimentary canal is usually simple of the mouth ; m, m, jaws. . . ' m its form, passing in a straight line from one end of the body to the other; and not exhibiting any distinction of stomach or intestine. It is often furnished with a number of little saccular appendages, placed along the greater part of its length ; these are probably 'secreting organs, as we do not find any others which can be regarded as having that character. Many of the Annelida are remarkable for the red colour of their blood ; this colour is not given, however, by red corpuscles, but exists in the liquor sanguinis (Amii. PHY- SIOL. § 229). Sometimes, however, the blood has rather a DEVELOPMENT OF ANNELIDA. 29? greenish tint ; and in many instances it is colourless, as in the Annulosa in general. 907. Comparatively little is known of the history of the de- velopment of the Annelida ; but there appears to be considerable variation in the amount of change they undergo after coming forth from the egg. The Branchiferous Annelides on first leaving the egg form an oval or roundish body, furnished with one or more bands of cilia, by the agency of which the little creatures swim about freely in the water. The body then gradu- ally becomes more elongated, during which additional bands of cilia often make their appearance. In a little time indications of the eyes and of the division into segments show themselves, a mouth and intestinal canal are formed, and by degrees the cilia disappear, and their place is usually taken by bristles of peculiar construction ; which however are only provisional or larval ap- pendages, and fall off when the worm approaches maturity. The number of segments then gradually increases, the new rings being always produced between the last and the last but one. In this way the body is elongated ; fresh organs are formed on its sides and on the head, until it acquires its permanent form. In the Leech and Earth- Worm, on the other hand, the develop- ment of the young seems to be nearly complete by the time that they leave the egg. — We find in this group the first dis- tinct appearance of that gemmiparous mode of reproduction which is especially characteristic of Zoophytes (ANIM. PHYSIOL. §§ 723- 730). The accompanying figure represents the mode of pro- PIG. 625.— SYLLIS PROLIFERA. pagation of the Syllis prolifera ; in which a young one is formed from the hinder part of the body of the parent, its head being 298 PROPAGATION AND CLASSIFICATION OF ANNELIDA. produced by a conversion of one of the segments of its body ; and this is gradually detached by a narrowing of the preceding joint. Previously to its separation, however, the young one often forms another bud from its own hinder part, in a similar manner ; and even three generations have been seen thus united. — From ob- servations recently made on another Marine Worm, in which a similar occurrence takes place, it would appear that the buds thus detached are, like the flowers of Plants, destined to Reproduc- tion only ; for whilst the parent continues to grow, to obtain its food, and to develope new buds from its hinder portion, these buds do not seem to grow into new individuals like their parents, - but, although possessing a head, mouth, and alimentary canal, they do not take in nourishment, their functions being restricted to the laying of eggs, from which new Nereids spring. 908. This Class is subdivided into Orders, according to the differences in general conformation and habits exhibited by the tribes which compose it ; and especially by the character and distribution of the respiratory organs. The first Order, DOKSI- BRANCHIATA, includes those which have the branchial appendages or gill-tufts disposed regularly along the body, sometimes extend- ing along its entire length, and sometimes restricted to the segments about the middle. This Order has been also denomi- nated Errantia, from the active habits of the animals composing it. — II. In the next, TUBICOLA, we find worm-like animals inhabiting fixed and permanent residences, like the testaceous Mollusca. The disposition of the gill-tufts around the head, and the absence of them along the body, is the principal character which distinguishes the animals themselves from those of the first Order. — III. In the third Order, TERRICOLA, the body is desti- tute of all external appendages, except some minute and almost imperceptible bristles ; for the respiratory organs are here deve- loped internally, the animal being usually formed to crawl upon the ground, instead of swimming through the water. — IV. And in the last, SUCTORIA, the body is destitute even of these bristles, but is furnished with a sucker at each extremity. ORDER DORSIBRANCHIATA ;— NEREIS, ETC. 299 ORDER I.— DORSIBRANCHIATA. 909. Of the foregoing Orders, the Dorsibranchiata appear, on the whole, to possess the most complete structure, as well as the most varied faculties ; and they also exhibit the forms most characteristic of the class. The head is almost always quite distinct from the trunk, and is furnished with one or two pairs of minute eyes, which are seen as black or reddish specks upon its upper side ; and it is also provided with several pairs of appendages (Fig. 626), as well as with complex instruments of mastication. These Marine Worms do not attain any considerable dimensions upon our coasts, rarely exceeding a few inches in length ; but in tropical climates, species no. 626.— HEAD are to ke met wjt^ Of comparatively gigantic pro- AND ANTERIOR ^ ° ° * SEGMENTS OF portions, having their bodies composed of 400 or 500 segments, and occasionally measuring four feet from one end to the other. They generally crawl with facility, and swim rapidly ; their chief habitations are among rocks and masses of shells; but some of them bury themselves in the sand, forming a sort of burrow, lined with muqps secreted from their bodies, which they quit in search of their prey. They are all carnivorous, and live on various small marine animals. 910. The NEREIDS, commonly known as Sea- Centipedes (Fig. 621), may be regarded as characteristic examples of this group. They are distinguished by having the gills in the form of leaf-like appendages or laminae, which are traversed by a net- work of vessels ; and every segment has, on either side, two tu- bercles, two cirrhi, and two tufts of bristles. They have none of that venomous power, which their name might be supposed to indicate ; but they are extremely voracious, and thread the most intricate passages and crevices among rocks and stones, in pursuit of their prey. In their turn, they are devoured by Fishes. — The EUNICID.E are nearly allied to the Nereidae; but have gills composed of filamentous tufts (Fig. 622, b\ instead of leaf-like plates. — The Eunice gif/antea of West Indian seas sometimes measures four feet in length ; and species of a much larger size are said to occur in the Southern seas. There are smaller species 300 DORSIBRANCHIATA ;— EUNICE, ARENICOLA, APIIRODITA. upon our own coasts. — In the AMPHINOMID^E, the gills hare the form of branching or arborescent tufts ; and these are disposed along the whole of the body. They are frequently coloured very brilliantly. The genus Euphrosyne has these branchial tufts very much developed ; and the body, instead of being long and narrow, has a broad and oval form. — The Aphrodita, the type of the family APHRO- DITIDJE, is an animal no. G27.-EUPHBOSYNE LATTREATA. . w6U-known on our coasts under the name of " Sea Mouse ; " probably on account of the large quantity of silky hairs with which it is covered. These hairs are of a very brilliant metallic lustre ; and their colours vary with the play of thp light ; so that this animal is scarcely surpassed by any in beauty of colouring. The back is furnished with two rows of large membranous scales, which somewhat resemble the elytra of Insects ; these inclose the gills ; but they are themselves concealed by the hairy covering just mentioned. The form of the body much resembles that of the Euphrosyne (Fig. 627). A large number of Aphroditre are not un frequently thrown up on our coasts after a gale of wind. In many species, the lateral setaa or bristles exhibit a beautiful structure, which admirably fit them for weapons of defence, being barbed on each side of their tips ; and each of these barbed setaa is inclosed in a smooth horny sheath, composed of two blades. — The ARENI- COLID^E are distinguished from the other families of this Order, by their having an enlarged rounded head, destitute of tentacles or eyes, and by their arborescent branchiae being confined to the middle part of the body. They constitute the nearest approach to the succeeding Order, as, although they do not form a tube for their residence, they dwell constantly in the sand, in which they burrow to a depth of twelve or eighteen inches, and, like the Tubicola, deposit their eggs in the midst of a small gelatinous mass, which serves as a protection to the younfc, and which is left on the surface of the sand, close to the little hssps which they throw up on retreating into their burrows. The common Arenicola is the well-known Lob-worm of the fishermen, who use it as a bait. ARENICOLA; PERIPATUS. — ORDER TUBICOLA. 301 The Arenicola is one of the Annelides most distinguished by the red colour of its circulating fluid ; and this colour is peculiarly seen in the branchial tufts, which have a beautiful crimson hue during the life of the animal. — Lastly, we may mention a very curious genus, Peripatus, which is probably to be placed in this Order, although it is a resident on land. In some respects it bears a resem- blance to the lu- lid»(§808),hav- PIG. 628.— PERIPATUS IULIFORMIS. . • ing legs adapted for walking, which present some appearance of articulation or jointing ; but in the softness of its body, and in the termination of the legs in tufts of bristles, it is evidently allied to the Ne- reidans. It forms the family PERIPATIDA:. ORDER II.— TUBICOLA. 911. The animals of this Order never attain to the same dimensions as the preceding ; and more is known of the casings which they form, than of the structure of the animals them- selves. One of the commonest of these is the shelly tube exuded by the Serpula ; which is formed of calcareous matter, resembling that of the shells of Mollusca, and apparently se- creted in a similar manner. In fact, it is often scarcely possi- ble to. distinguish between the shell of a Serpula and that of a Vermetus (Fig. 672). The tubes of the Serpulae (Fig. 629) are generally found clustering in masses, attached to the surface of stones, shells, or other bodies, which have been immersed for any length of time in the sea ; they are usually more or less contorted in form, varying in this respect according to the position in which they grow ; but they are always closed at one end, which tapers to a point, the wide end being open to give exit to the head and mouth of the inhabitant. The animal which forms this shell, and resides in it, has its branchial filaments or gill- tufts all assembled round the head ; where they form a pair of 302 ORDER TUBICOLA ; — SERPULA, SPIRORBIS. Fiu. 629.— GROUP OF SERPULA. most elegant fan-like appendages, which usually possess very brilliant colours. At the base of each series, there is a fleshy filament ; and one of these, on the right or left side indifferently, is prolonged and dilated at its extremity into a flat disc, which fits to the mouth of the shell, and serves to close it when the animal is withdrawn into the tube. The body of the animal is composed of a great number of seg- ments ; but these are for the most part unprovided with any appendages. The anterior segments, however, which are much thicker than the rest, are furnished on each side with bundles of stiff bristles. The largest species of this, as of the preceding groups, are found in tropical regions, where they usually form their habitations in the midst of Corals, and lengthen their tubes as the Coral is built up around them ; their length is sometimes as much as three feet; and their expanded gill-tufts are of extremely vivid colours, strongly resembling the most brilliant Carnations in general aspect. These are usually extended beyond the mouth of the shell, in order to obtain the full influence of the water, for the aeration of the circulating fluid ; but if they be touched, they are immediately drawn in, and the mouth of the tube is closed by the disc just mentioned. Numerous smaller species are found on our own coasts ; and some of these are remarkable for the brilliant hues of their expanded gills. — A minute white spiral shell may be frequently seen upon the flat fronds of sea- weeds ; this is the Spirorbis, the animal of which is nearly allied to that of the Serpula. The food of these Annelids probably consists of Animalcules and small marine animals ; together, per- iiaps, with particles of dead animal matter, which are brought towards the mouth, by the currents created by the cilia on the branchial tufts : their masticating apparatus is much less complete than that of the Dorsibranchiata. 912. Besides the Serpulse, we have to mention several other TUBICOLA; — TEREBELLA, AMPHITRITE, PECTINARIA. 303 animals of this group, which do not form their tubes by a calca- reous exudation from their own bodies, but by cementing together particles of shell, sand, small pebbles, &c., by means of a gluti- nous secretion. We may first notice the Sabella, which seems to have some power of exuding calcareous matter ; and forms its shell partly of this material, and partly of granules of clay or fine mud. In the arrangement of its gill-tufts, it bears a strong resemblance to the Serpula. The Terebella forms its tube entirely by the agglutina- tion of grains of sand, pieces of shell, &c. ; and some species live in groups, so Fio. 630.— TKRKBBLLA MEDUSA, in its tube. that their clustering-tOge- ther forms solid masses, which may go on increasing to a considerable size. The gills are here smaller, and are placed behind the head, having the form of small arborescent tufts ; and the head is furnished with numerous tentacula, which are capable of being greatly extended. These probably assist the gills in the aeration of the blood, as they pre- sent a large surface to the water ; but their chief use appears to be the prehension of food. The shelly tubes usually have little branches near their summit, through which the gills and the ten- tacula pass out. The Tubicola of the genus Amphitrite are distinguished by their large golden-coloured setae, disposed in a comb-like series, or in a crown, or in one or several ranges on the front of the head ; these probably serve them for defence, and may give assistance in locomotion. Many of these animals, belonging to the sub- genus Pectinaria, are less con- fined to one spot than the pre- j.- ,1 • ,i_ i • i ceding; their tubes, which are composed of fine grains of sand cemented together with great regularity, are simple cones open at both endfc and not attached ; FIG 631 — TKREBELLA VARIABILIS. 304 PECTIN ARIA. —ORDER TERRICOLA. and they carry these about with them, when roaming in search of food. It is perhaps in consequence of their locomotive powers, which give them a greater facility of selection, that they construct their shelly tubes with so much more regularity than other Annelidans. These tubes, usually about two inches long, may be frequently picked up on our shores. Some of this group, however, are fixed like the other Tubicola, and form their tubes less regularly. Their bodies are doubled up, as it were, within these envelopes ; so that the intestine terminates in a tube which is curved back over the head. The young of these creatures, when just hatched, are all active, ciliated animalcules, furnished with eyes, which they lose on approaching maturity. ORDER III.— TERRICOLA. 913. The Annelida of this Order have a cylindrical body, tapering to a point at its extremities, and furnished only with several rows of bristles ; these are frequently invisible to the naked eye, but may be distinguished by the resistance they make when the finger is passed along the body from behind forwards, — their points being directed backwards, in order to give the animal a firm hold of the earth through which it is boring. The head of tnese animals is not distinct from the body ; and they have neither eyes, antennae, mandibles, cirrhi, nor external gills. Their bodies, however, are distinctly divided into segments ; and these are marked by minute spots on each side (Fig. 632, a\ which are apertures leading to small respiratory sacs, on the walls of which the blood is submitted for aeration to the air or water received into them. This Order includes only two princi- pal groups, the Earth- Worms and the JVaids, — the former be- ing inhabitants of the land, and the latter of the water. 914. The Earth- Worms, which nearly all belong to the genus Lumbricus, generally live beneath the surface of the ground. In boring, the Worm insinuates its pointed head between the par- ticles of the earth, penetrating like a wedge ; and in this position, the anterior part of the body is fixed by the spines or ORDER TERRICOLA; — KA*UTH-WOUMS. r,co bristles, of which there are four pairs on each segment (Fig. 632, &). The hinder parts are then drawn forwards by a shorten- ing of the body, — a movement which the spines do not oppose ; this swells out the anterior segments, and forcibly dilates the passage into which the head had been already thrust. The spines upon the hinder rings then take a firm hold upon the walls of the hole into which they have been drawn ; and this part of the body being now made a fixed point, the head is again forced forwards by the powerful contraction of another set of muscles ; and by a repetition of this process, the animal easily makes its way through substances, which it would at first have seemed impossible for it to penetrate. The muscles, by which this action is performed, are disposed in two series ; the arrange- ment of which is very characteristic of the Articulata in general, though it is less obvious in the higher classes, whose locomotion is chiefly effected by the action of the extremities. The muscles of one series are longitudinal in their direction, passing from segment to segment, and serving by their contraction to draw the segments together, in such a manner as to shorten the body, at the same time increasing its diameter. The muscles of the other series have a contrary direction, forming rings round the body, and tending by their contraction to diminish its diameter, and consequently to increase its length. 915. The burrowing of Earth-worms is a process exceed- ingly useful to the Gardener and Agriculturist; and these animals are far more beneficial to Man in this way, than they are injurious by devouring the vegetables set in the soil. They give a kind of under-tillage to the land, performing the same below ground that the spade does above for the garden, and the plough for arable land ; and loosening the earth, so as to render it permeable to air 'and water. It has been lately shown, that they will even add to the depth of soil ; covering barren tracts with a layer of productive mould. Thus, in fields which have been overspread with lime, burnt marl, or cinders, these substances are in time covered with finely-divided soil, well adapted to the support of vegetation. That this result, — which is commonly attributed by the farmers to the " working-down " of the materials in question, — is really due to the action of the Earth- 506 ORDKU TERRICOLA ; EARTH-WORM. worms, appears from the fact that, in the soil thus formed, large numbers of "worm-casts11 may be distinguished. These are produced by the digestive process of the Worms ; which take into their intestinal canal a large quantity of the soil through which they burrow, extract from it the greater part of the decaying vegetable matter it may contain, and reject the rest in a finely-divided state. In this manner, a field, manured with marl, has been covered, in the course of 80 years, with a bed of earth averaging thirteen inches in thickness. 916. It is commonly supposed that the Earth- Worm may be multiplied by the division of its body into two pieces, of which each will continue to live. This does not, however, appear to be the case with regard to the common species. If it be divided across the middle, when in motion, each part will continue to move for a time ; but only the piece which bears the head will be found alive after a few hours. This forms a new tail ; and soon shows little sign of injury. But if the division be made near the head, the body will re- main alive, and will renew the head ; and the head, with its few attached segments, will die. — There appear, how- ever, to be some species, in which this reproductive power is sufficiently great to produce a new head and body from even a small portion of the original ; so that it is said that -above twenty indi- viduals have been prd&uced in this manner, by the division of a single one into as many parts. This power is even greater in the Naids ; which also produce buds, that separate from the parent by sponta- neous division, as in the Syllis prolifera (§ 907). — The propagation of the Earth- worms presents some other very remarkable peculiarities. The FIG. 632.— LUMBRICTJS TER' RESTRIS, OR EARTH- WORM; 6, anterior segments magnified, showing the bristles directed backwards; c, egg, enclosing two young ; d, escape of young worm from the egg. EARTH-WORM, NAIS. ORDER SUCTORIA. 307 ova, when they have been fertilised, quit the ovarium, not by oviducts or passages leading outwards, but by finding their way into the loose tissue of the body, beneath the muscular layer ; through this they are propelled by a series of strong undula- tions, until they reach a sort of receptacle, in which they undergo the first part of their development, and within which, in some species, the eggs are hatched, so that the young come forth alive. The eggs are provided with a curious valve-like structure at the end through which the young worm emerges ; and it is remark - able that, in a great number of instances, two embryos may be observed in a single egg. - 917. The genus Nais is nearly allied to the Lumbricus ; but the worms which it includes are aquatic in their habits, living in holes which they perforate in mud at the bottom of water. Some of them have small black points upon their heads, which have been regarded as eyes. ORDER IV.— SUCTORIA. 918. This Order contains the common Leech and its allies, which are all animals of aquatic habits, but not all agreeing in its blood-seeking propensities. The group derives its name, as already stated, from the suckers which terminate the two ex- tremities of the body, and which constitute its chief means of locomotion ; for having fixed its anterior extremity, the animal draws the posterior one close up to it, by bending its body, — and then, fixing the latter, re-advances the first, by straightening and extending the body. In this manner the Leech can advance much more rapidly over solid surfaces, than the Earth- Worm can by its crawling movement ; and it can also swim with facility, by an undulating movement of the whole body. 919. The Leech, in its general structure, bears a considerable resemblance to the Earth-Worm ; but differs as to the conforma- tion of its mouth and digestive apparatus, which are in accord- ance with its suctorial habits. Its mouth is situated in the middle of the cavity of the anterior sucker ; and three little 308 ORDER SUCTORIA; — LEECH. cartilaginous bodies, usually called teeth, but more properly jaics^ are seen to be disposed around it, in such a manner that the FIG. t,;;3. SANGUISUGA OFFICINALIS. three edges form three radii of a circle. Each of these has two rows of minute teeth at its edge, so that it resembles a small semi-circular sav^ It is imbedded at its base in a bed of muscle, by the action of which it is worked, in such a manner as to cut into the skin, — a sawing movement being given to each piece separately. It is in this manner that the tri-radiate form of the leech-bite is occasioned ; each ray being a separate little saw. The lacerated character of the wound is very favourable to the flow of blood ; which is further promoted by the vacuum created by the action of the sucker. The alimentary canal is straight ; but is furnished, at its posterior portion, with a large number of little sacs, or caeca, opening from it. The operation of digestion is extremely slow, notwithstanding the rapid and excessive manner in which the Leech fills its stomach ; a single meal of blood will suffice for many months ; nay, more than a year will sometimes elapse, before the blood has passed through the alimentary canal in the ordinary manner, during all which period so much of the blood as remains undigested in the sto- mach continues in a fluid state. — Leeches are furnished with eight or ten simple eyes, which may be detected by the aid of a magnifying-glass, as a semicircular row of black points, situated above the mouth upon the sucking surface of the oral disc ; this position is evidently calculated to render these organs of use in the discovery of food. Each of these visual specks would seem to be merely an expansion of the extremity of a nerve, derived from the cephalic ganglia, spread out beneath a kind of cornea formed by the delicate and transparent cuticle, and having behind it a layer of black pigment; nothing like a crystalline,- lens can be discovered ; so that the vision of these animals must LEECHES. — CLASS OF ENTOZOA. 309 be extremely imperfect. — The greater number of the Leech tribe are inhabitants of fresh water ; some, however, are only found in the sea ; others live in moist situations near stagnant water, pursuing Earth- Worms, &c. ; and there is one small species, entirely terrestrial, which inhabits the woods of Ceylon, and attacks men and horses that are passing through them, in such a manner as to become, from its great voracity, one of the most troublesome pests of that fine island. The species of the genus Cfepsine, which inhabit fresh waters, suck the blood of the com- mon Pond-snails. Most of the marine species are parasitic in their habits ; the Malacobdellce attaching themselves to bivalve Mollusca, whilst others infest fishes, and one, the Udonella call- gorum, feasts upon the juices of a small Caligus(^ 889), which is itself parasitic upon the liolibut. CLASS OF ENTOZOA. 920. This class derives its nan e from the peculiar mode of existence of the animals composing it ; most of them being inhabitants, during their whole lives, of the bodies of other animals, generally of higher organisation, from the juices of which they derive their nourishment. Many of these possess a distinct worm-like form ; the body being much prolonged and exhibiting a slight indication of a division into segments, and the mouth being situated at one extremity. These, therefore, evidently belong to the Articulated series. There are others, however, which, in their general form and the simplicity of their organisation, seem scarcely to agree with the Articulate type of structure. 921. There is a very interesting group, consisting of the genus Planaria and its allies ; which is placed in this class on account of its general conformity with it in structure; although not agreeing as to the residence of the animals composing it, — ihese not being inhabitants of the bodies of other animals, but swimming freely in waters of the ocean, as well as in VOL. n. z 310 PLANARIA.— ENTOZOA PROPER. streams and ponds, and crawling upon their banks, or upon floating substances. The body is flat, and three or four times as long as it is broad. Within its soft tissue are channelled out, not only a complex digestive cavity, but also a system of vessels which absorb fluid from its walls, and convey it through the system. The stomach opens, not by a mouth at one end, but by a sort of sucker projecting from the middle of the body ; and through this the Planaria imbibes the juices of various aqua- tic • animals which it attacks ; mastering even the most active little worms (such as the Nais) by twisting its body round them. — The most curious parts of the economy of these animals consists in their power of reproducing parts that have been lost, and of repairing injuries ; which seems to be almost as great as that of the Hydra among Polypes. They may be divided into three parts ; of which the first shall contain the two minute spots which are believed to be eyes ; the middle one the sucker ; and the posterior one the reproductive apparatus ; and in a short time, each part will develope itself into a new individual, perfect in all its parts. It may be partially split longitudinally from either extremity, so that two heads, or two tails, or both in com- bination, may be formed, all uniting at the middle point, but each being complete in itself. 922. Although, for the sake of brevity, we have retained the class of Entozoa as a single section of the Articulate series, and the animals included in it agree in at least one important anato- mical character, namely, the absence of transversely striated muscles, it must be admitted that they present very great differ- ences both in form and structure, and the majority of modern naturalists are agreed in regarding them as forming two inde- pendent classes, which have been denominated by Vogt, NEMA- TELMIA or Round-worms, and PLATYELMIA or Flat-worms. In the NEMATELMIA, which present the nearest approach in form to the lower members of the preceding class, the body is elongated and cylindrical, and the skin often exhibits indications of segmentation in the form of slight wrinkles. There is usually a distinct intestinal tube with an orifice at each end, in some species a vascular system has been detected, and in most there NEMATELMIA ;— NEMATOIDEA. 3 1 1 are distinct traces of a nervous system. The sexes are always on separate individuals. In the PLATYELMIA, on the contrary, the body is almost always flat and broad, covered by a soft skin, often containing calcareous corpuscles, but destitute of any indi- cations of segments. The intestinal canal has only a single orifice, and the nervous system is far less distinct than in the Nematelmia. These animals are hermaphrodites. 923. Section I. NEMATELMIA. — These worms, which are all parasitic in their habits, form three orders. The GORDIACEA, or Hair-worms, have the body so extraordinarily long and thin as to resemble horse-hairs, and their intestine has no posterior orifice. They are parasitic in the bodies of different species of insects, where they live amongst the parenchyma exterior to the intestine. When ma- ture, they quit the bo- dies of their victims and proceed to deposit their eggs in long FIG. 634.-GORDIU8 AOTATICUS. a. t»ii. chains in the water, or in moist situations. If the weather be dry at the time of their escape, they often be- come dried up until they form slender horny threads, which arc so brittle as to be easily broken ; but even in this state they re- tain the principle of life, and the occurrence of a shower of rain is sufficient to restore them at once to activity. The young are of course hatched from the eggs, in the water or damp earth in which the latter are deposited, but they soon penetrate into the body of some insects, in the interior of which their development takes place. — The NEMATOIDEA are distinguished from the pre- ceding by the existence of an anal orifice, and by their shorter and thicker form. This order includes several species which are parasitic in the intestines of Man. Such are the Ascaris lum- bricoides, well known as the Round-worm, which is of the size and form of a small earth-worm, whence its specific name ; and the Oxyuris rcrmicularis, or Thread-worm, which frequently occurs in great numbers, especially in children, to whom it is exceedingly troublesome. Other species live in closed organs of 312 STRONGYLUS ;— FILARIA.— ACANTHOCEPHAL A. the body, but these are rarely found in man. Of this nature is the Strongylus gigas, which inhabits the kidneys of pigs, and sometimes occurs in the human subject. This worm is usually about ten inches in length, but occasionally measures two or three feet, and, as might be expected, is extremely injurious to the animal in which it takes up its abode. We may also notice the Filaria or Guinea-worm, which burrows in the flesh of man and other animals in warm climates, especially in Africa and the South of Asia. It usually measures five or six feet in length, but is said sometimes to be much longer. When it shows itself at the surface, it is extracted very slowly and carefully, by wind- ing it round upon some small object ; if broken during this operation, it is said to produce very painful consequences. — The mode of development and transmission of the Nematoid worms is still involved in much obscurity. In some instances the worms ap- pear to bore through the wall of the intestine, in order to deposit their eggs in the tissues or blood-vessels of their host ; the young animals then enclosing themselves in a minute cyst, from which they escape after a time in order to return to the intestine. This is supposed to be the origin of the Trichina spiralis, a small encysted worm found on the muscles of the human subject. In other cases the worms are passed with the excrements, espe- cially at certain seasons of the year, when they probably disse- minate their eggs in the outer world ; and these, or the young brood, may be taken again into the stomach with raw food or water. The little Oxyuris is even known to creep voluntarily out of the intestine, and may thus perhaps find admission to that of a new victim. The Filaria is found principally in the lower extremities of the body, so that its young probably inhabit the water, and attach themselves to the legs of people when wading or washing their feet. — The third Order, the ACANTHOCEPHALA, includes only the single genus Echinorhynchus, composed of rather thick, annulated worms, which appear to be totally desti- tute of an intestine. These curious parasites, which are found principally in the intestines of Fishes, are furnished with a pro- trusible proboscis, armed with rows of recurved spines, which serve to hold the animal firmly in the intestine of its host. Be- PLATYELMIA 5—TURBELLARIA : TREMATODA. 313 neath the skin is a singular areolar structure, which is probably connected with the absorption of fluid through the integument, this being apparently the only way in which these parasites can obtain their nourishment. Some species of the group arc para- sitic on Mammalia, and one of these found in the Pig attains a length of no less than eighteen inches. — The so-called Eels of vinegar and sour paste are referable to this group, in regard to the simplicity of their structure and their worm-like form ; al- though their habitation is so different. There is also a little worm-like animal closely allied to these, which is found in dis- eased ears of wheat, and which possesses remarkable tenacity of life, being revived by moisture after having been dried for almost any length of time. 924. Section II. PLATYELMIA. — Of the Flat-worms, we may likewise distinguish three Orders. — Of these the first, that of the TURBELLARIA, includes the non-parasitic species, which are dis- tinguished from their parasitic relatives by the possession of cilia on the surface of the body. To this Order belong the Planaria already referred to (§ 921), together with a number of nearly allied species, the majority of which are inhabitants of fresh water, whilst a few are found in the sea, and several are ter- restrial in their habits. The Nemertida or Ribbon-worms, which are also placed with the Turbellaria, differ from the Planariae in the elongated ribbon-like form of their bodies, and in the posses- sion of an anal opening. They are predaceous in their habits, and some of them attain a considerable length. — The TREMATODA, forming the first Order of the parasitic Flat-worms, have a rounded, elliptical or oval body, covered with a soft skin, which usually contains calcareous corpuscles, and furnished with one or more sucking discs, which are often supported by a horny framework. The intestine is generally forked at a little distance behind the mouth, and the two branches sometimes end in blind extremities, and sometimes meet at the posterior part of the body, so as to form a complete circle ; in some cases the intestine is minutely ramified. The Distoma hepaticum or Fluke, which commonly infects the livers of sheep, and is also found in man, is a well-known example of this group, most of the worms belong- 314 PLATYELMIA ; — TREMATODA ; CESTOIDA ing to which are found in the parenchymatous organs of animals, although some infest their intestines. In the development of some of the Trematode worms, we meet with an alternation of generations, as it is called, of a very singular nature. The yelk gives origin to a flat, ciliated embryo, furnished with a pair of eye-like points at the anterior extremity. In the interior of this a sac-like body capable of motion is produced (by gemmation) ; and this, getting access to the body of some animal different from the one in which its parent was parasitic, gives origin by another process of gemmation to a multitude of little granules, which be- come developed into small tailed animalcules, identical with those which were formerly described as Infusoria under the name of Cercarice. These break out of their sac-like parent (or nurse as it is called), and swim about freely in the water, until they re- commence a parasitic existence by boring their way into the aquatic Iarva3 of Insects. Here they lose their tails, and enclose themselves in a little cyst, to wait until the insect inclosing them is devoured by some predaceous animal (fish, or bird), in the body of which they are able to continue their development. The most singular species of this group is the Diplozoon paradoxum, a creature which consists of two exactly similar halves, united by a narrow band in the middle of the body, as though two separate animals had grown together at this point. This curious animal is parasitic on the gills of the Sea Bream. 925. In the CESTOIDEA, forming the third Order of Flat- no. 635.— TJENIA SOLIUM. worms, the process of development is no less curious, although, in many cases, the number of transmigrations appears to be rather DEVELOPMENT OF TAPE-WORMS. 315 less than in those Treraatoda whose history has been investigated. In their mature state, when they are known as Tape-worms (Fig. 635), these creatures form an elongated strap-like body, divided into numerous segments, with two longitudinal canals running down the sides of the body, and united in each segment by a transverse canal. At the anterior extremity, which is much narrowed, there is a sort of head furnished with sucking discs, and usually with a double crown of hooks, by the agency of which the parasite is firmly anchored to the intestine of its victim. The Tape-worm in this form is not however to be re- garded as an individual animal, but as a colony ; each segment being an individual in the ordinary sense of the term, produced by gemmation from the head, and gradually removed to a greater distance from the point where it was first formed, by the constant production of similar segments in the same way. Each segment is in fact a complete hermaphrodite, and, when mature, contains an immense number of eggs ; on arriving at this condition it is cast off from the colony, acquires a power of locomotion, and quits the intestine of the animal which has hitherto harboured it, in order to distribute its eggs in situations whence they may be introduced into the bodies of other animals. With but few ex- ceptions, however, the animals adapted for the early development of the embryos of the Tape-worms, are not the same as those in which the mature parasites are met with ; the latter are always found in carnivorous, and the first products of development princi- pally in herbivorous animals, not in the intestinal canal, but in the closed and parenchymatous organs of the body. A s the mode of de- velopment of these parasites is exceedingly curious and interesting, and a knowledge of it is of the highest importance in medicine, we shall give a short abstract of its leading peculiarities. The seg- ments, which are now called proglottides,, when thrown off from the mature Tape-worm disseminate their eggs in various places, as they crawl about upon the ground or on plants. These eggs are swallowed by herbivorous animals with the grass or other plants which constitute their food, and on reaching the stomach the little embryos escape from them. The embryos are small vesicles, furnished with six minute hooks or spines, by the agency of 316 DEVELOPMENT OF TAPE-WORMS. which they make their way through the walls of the stomach and the tissues of the body until they reach the organ in which their development is to take place, or, getting into the blood- vessels, allow themselves to be carried along by the stream to some suitable locality. Here they establish themselves, and soon afterwards the little vesicle swells and becomes surrounded by a cyst, formed by exudation from the tissues of its host. A curious process of gemmation then begins in the little bladder, the result of which is the production of a head resembling that of the Tape-worm, but turned into the cavity of the vesicle, which is filled with a fluid resembling the white of egg, and serves both as a reservoir of nourishment and as a protective covering for the budding head. In some cases nothing but the head is produced ; in others a neck of considerable length, with indications of segments, is formed ; in some again the vesicle only produces one head, whilst in others it attains an enormous size and gives origin to a multitude of such productions. These bladder-like parasites have long been known under the name of Cystic- worms (Cystici), and regarded as nearly allied to the Tape-worms ; but it is only recently that it has been discovered that they are mere steps in the development of the latter. The worm in this stage is now gener- FIG. 636.— CYSTICERCUS CEr.LTJLOs.aB 5 11 a • j. j 7 T i • «, head enlarged. ^"7 denominated a scolex. In this condition it remains until the animal in which it harbours is devoured by some particular carnivorous animal, when the head, which up to this period has been turned into the vesicle, is protruded and attaches itself to the intestine of its new host by means of the hooks and suckers with which it is provided (Fig. 636). The vesicle (and neck when present) is then cast off, and the head proceeds to develope a series of segments which in course of time form the true Tape-worm colony as first described. This is called the Strobila. Some differences are exhibited, especially in the second stage, by the different species of Cestoidea, especially those which pass this PLATYELMIA; TAPE-WORMS. 317 period of their existence in cold-blooded animals ; in these no vesicle is formed, but in some there is a flat band-like appendage, and in others the little vesicle of the embryo fits closely over the newly formed head. 926. Several species of Tape-worms inhabit the intestines of man. Of these the best known is the Tcenia solium or common Tape-worm (Fig. 635), which sometimes .measures eighteen or twenty feet in length. The Bothriocephalus latus, or Broad Tape-worm, is found only in particular districts on the continent, especially in Holland, Poland, and Switzerland ; it is as long as the common species. A third large species has been described, under the name of Tcenia mediocanellata, by D. Kiichenmeister of Zittau ; this appears to increase very rapidly, as, in one case reported by the above author, a patient was calculated to have passed on an average twenty proglottides or segments per day for eighty days ; or taking the number at fifteen per day, this would give 1200 proglottides; or reckoning these at 1 inch in length, 100 feet of worm in the above period of time, being at the rate of 1 £ foot per day. This enormous product was all furnished by a single worm. Of the Cystic forms (Scolices) a few are also parasitic upon the human subject; such are the Cysticercus celluloses (Fig. 636) and the Echinococcus. The former is also found in various herbivorous animals, but especally in the Pig, to the flesh of which it communicates the diseased appearance known as measles. The Echinococci occur principally in the livers of various domestic animals, but they also commonly attack man in the island of Iceland. They form large bladders of fluid, from the inner walls of which an immense number of minute heads are developed ; and in one form or species, the original bladder not only produces heads, but also smaller vesicles, which again give origin to heads. The Ccenurus cerebralis is another vesicular form, which attains a large size and produces a great number of heads, but in this species the budding takes place on the outer side of the bladder. The Ccenurus inhabits the brain of sheep, to which it gives the pe- culiar disease known as the vertigo or staggers. 318 ROTIFERA, OR WHEEL-ANIMALCULES. CLASS OF ROTIFERA. 927. The class of ROTIFERA, or Wheel- Animalcules and their allies, is certainly to be regarded as belonging to the Articulated division of the animal kingdom ; although the characters of that group are by no means distinctly marked in it. That these beings possess a structure much more complex than that of the Infusoria, to be hereafter considered (Chap. XXVI.), there can be no doubt whatever, and indeed some authors have even pro- posed to arrange them with the Crustacea. That this complexity of structure was for a long time overlooked, was owing to the minute size of the animals in question ; scarcely any of them ex- ceed a line in length, and many are less than -^^ of an inch. Nearly all the species of this class are aquatic in their habits, some living only in salt water, others frequenting stagnant ponds, and others appearing in vegetable infusions, where they gener- ally succeed animalcules of inferior organisation. 928. The great transparency of the bodies of the ROTIFERA permits their general structure to be easily recognised. They have usually an elongated form, similar on the two sides. At the anterior extremity, we observe one or more rows of vibratile cilia, usually arranged in a circular manner. When these are in motion, an appearance as of revolving wheels is produced, from which the class derives its appellation ; and this is particularly evident in one of its commonest forms, usually known as the Wheel- Animalcule, which possesses a circular row of cilia on each side, (Fig. 637, b). In many species we find a prolonga- tion of the body in front, extending beyond the ciliary apparatus ; this, which sometimes bears one or more red spots, that are believed by Ehrenberg to be eyes, may be regarded as a head (Fig. 637, a). The body is covered by a double envelope, both layers of which are extremely thin and flexible in some species ; whilst in others the outer one seems to possess a horny consist- ence, and may even contain silicious or flinty matter, like the sheaths of the lower Infusoria. In the former case, the whole STRUCTURE OF WHEEL-ANIMALCULE. 319 integument is drawn together in a wrinkled manner, when the body is shortened ; in the latter, the sheath acts as a kind of cell, into which the head and ciliary apparatus can be completely retracted. These last would seem to have some relation with the Polypifera; and we shall hereafter see that the affinity may be regarded as very close. On the other hand, the former present an external resemblance to the vermiform tribes ; which, also, will be found to increase on a closer examination ; and there are also species, of which the sheath bears a strong likeness to that of some Entomostracous Crustacea (§ 882). Hence we may regard this group as con- necting the Articulated classes with the Zoophytes. This re- semblance is heightened by the fact that many of these little creatures are sessile or attached to one spot during life, and most of these envelope themselves with a gelatinous case, from the top of Which the upper part of the body c> water-siphon ; d, masticating appara- J tus; «, salivary glands; //, intestinal With the rotatory Organs IS pro- canal ;g, its dilated termination; ft, glan- truded. FIG. 637 — WHKKL AMMALCULKH ; A, with the wheels expanded ; B, with the dulnr apparatus surrounding it ; i, young ones nearly complete ; A-. ecrgs; I. tail. 929. As a characteristic illus- tration of the class, we shall select the common Wheel- Animal- cule, Rotifer vulgaris. The body, when extended, possesses considerable length in proportion to its diameter, and has much of the Vermiform or worm-like aspect ; this is increased when a slight contraction draws the external membrane, which is here thin and very flexible, into transverse wrinkles, that seem to in- dicate the segments of the trunk. The posterior extremity is 320 STRUCTURE OF WHEEL-ANIMALCULE. prolonged into a tail, possessing three joints, each of which has a pair of prongs or points. These joints can be drawn up within each other, like the sliding-tubes of a telescope. Within the ex- ternal integument there are four longitudinal bands running from end to end ; these are probably bundles of muscular fibre, by the contraction of which the body may be shortened. The cilia are disposed in two circles, forming what are termed the wheels. By the successive vibration of these, the appearance of a continual rotation is produced ; and their action creates rapid currents in the surrounding fluid, by which the supply of food is obtained. A sort of whirlpool is created by each .wheel, which brings towards the mouth the minute animalcules and other particles floating in the neighbourhood ; and those which are not swallowed, are carried off by a return-current. Between the wheels, the head is occasionally protruded, bearing the two red spots supposed to be eyes ; and on its under surface there is a projecting spike (c), which is observed to be tubular, and which is believed to act as a siphon for the introduction of water into the general cavity, for the purpose of respiration. The oeso- phagus terminates in a sort of gizzard, provided with regular teeth at its entrance (d). These teeth are two in number on each side, and are fixed upon hard jaws, moved by powerful muscles, so as to work between each other. All the food which is swallowed is submitted to their action, before it enters the first stomach ; and when the cilia are in operation, these jaws are always in regular movement. From the first stomach there passes off in the Rotifer a long straight intestine (/,/)> whidk terminates without any dilatation except near its close (#), just at the commencement of the tail. But in many other Rotifera we find the gizzard opening into a larger cavity, which may be regarded as the true digestive stomach. Near the termination of the intestine is the opening of the passages, by which are ex- truded the eggs (k), that are formed in the large ovaria. These eggs often attain so great a degree of development, while yet within the body of the parent, that the ciliary movements of the embryo may be seen ; and the young may be said to be born alive, being capable of active locomotion, and of obtaining their STRUCTURE OF WHEEL- ANIMALCULE. 321 own food, as soon as they quit the body of the parent. Besides the longitudinal muscular bands, we observe transverse lines crossing the body at intervals, which might be supposed to possess the same character, and to contribute to the elongation of the body by contracting upon the contents of the visceral cavity. Nervous ganglia are suspected to exist in this animal in the neighbour- hood of the eyes ; but they cannot be seen in this species as dis- tinctly as in some other Rotifera. 930. This animalcule, from the activity of its habits, and the variety of the movements it performs, is one of the most interesting objects which commonly present themselves to the microscopic observer. Sometimes it fixes itself by its forked tail to some solid basis, and then sets its wheels (as they appear) into rapid revolution ; at the same time bending its flexible body in various directions, so as to create currents in different parts of the surrounding water. In this manner it draws into its gullet the unfortunate Animalcules which have been affected by the whirlpool it has created ; just like (it has been amusingly remarked by Spallanzani) a certain species of Whale, which, after having driven herrings into a bay or strait, by a blow of its tail produces a whirlpool of vast extent and great rapidity, which precipitates them down its open mouth. The food thus taken in passes at once towards the stomach, and is submitted to the action of the jaws at its entrance, by which it is broken down. By keeping a Wheel- Animalcule for a few days in pure water, it will become almost perfectly transparent in every part, and its alimentary canal will be completely emptied. If some water containing the green or red Cercarice, or any other small coloured animalcules, be then added, its voracity will be very amusingly exhibited. They will be very distinctly seen passing into the alimentary canal, as fast as the animal can masticate them ; and this will become distended with their coloured substance. It cannot be questioned that the ciliary movement is here entirely subject to the will of the animal. When satisfied with the sup- ply of food it has obtained, the movement of its wheels no longer continues ; and the lateral projections on which they are situated then usually fold themselves inwards, so as to conceal them. 322 STRUCTURE OF WHEEL-ANIMALCULE. The form of the animal — the head still projecting — then closely resembles that of a Leech ; and the movements which the Rotifer performs in this condition, are by no means unlike those of that animal. Sometimes it detaches itself altogether, and swims freely through the fluid, as if in search of a new pasture. In other instances it attaches itself by the head, which is furnished with a sort of sucker for the purpose ; and then, by shortening the body, draws up the tail into close proximity with it. It then attaches the tail, and, detaching the head, extends the body so as to project the head to a considerable distance, where it takes a new hold of the surface upon which it thus creeps. The rapidity and precision with which these movements are executed display a considerable amount of muscular energy on the part of the animal, as well as of that capability of adapting its opera- tions to circumstances, which indicates sensations of some acute- ness. When the body is elongated to its full extent, the intestinal canal rvms nearly straight ; and the eggs, which may usually be seen by its side, lie apart from one another. But, when the body is contracted, the alimentary tube becomes serpentine, and the eggs by its side appear to be in close contact. The great amount of muscular contractility, and the flexibility of the integument in this animal, enable it thus to contract itself more than most of its class. It is not unfrequently seen to assume quite a globular form ; and this is its usual aspect when it dies, or when the water evaporates. — The reproduction of the Rotifer is not accomplished by spontaneous subdivision, or by the production of buds, such as we shall see to occur in the Polypes and Infusoria ; it takes place only by eggs, in the manner already mentioned. Although not many eggs are produced at once, yet these so speedily become capable of producing others in their turn, that the multiplication of these beings takes place with extraordinary rapidity. A cal- culation, made by Ehrenberg, from data furnished by experiments upon another species, will be presently given (§ 933). 931. The capability which these Animalcules possess, of being revived, after having been entirely dried up, or desiccated, is one of the most curious points in their history ; since perhaps, with the exception of the Bear animalcules (§ 841), no other TENACITY OF LIFE IN ROTIFERA. 323 animals of an organisation so complex appear able to preserve their vitality under the same treatment. The fact was first observed by Leeuwenhoek ; and it has been since confirmed by other observers. Ehrenberg doubts, however, whether a com- plete desiccation could have taken place ; thinking it impossible that the animal should survive it. The following statement of my own experience on the subject may not, therefore, be unde- sirable. In the summer of 1835 I placed a drop of water, con- taining a dozen specimens of the Rotifer vulgaris, on a slip of glass ; and allowed the water to dry up, which it did speedily, the weather being hot. On the next day I examined the glass under the microscope, and observed the remains of the animals coiled up into circles, — a form which they not unfrequently assume when alive, — but so perfectly dry that they would have splintered in pieces if touched with the point of a needle, as I had before observed in similar experiments. I covered them with another drop of water ; and in a few minutes ten of them had revived, and these speedily began to execute all their regular movements with energy and activity. After they had remained alive for a few hours, I again allowed the water which covered them to dry up ; and I renewed it on the following day with the same result. This process I repeated six times ; on each occasion one or two of the animals did not recover ; but two survived to the last ; and with these I should have experimented again, had I not accidentally lost them. — It is possible that the species on which Ehrenberg and other foreign naturalists have experi- mented, may not be the same as that which I and other English observers have used. Something, too, appears to depend upon the season and the general condition of the animal; for, on repeating the experiment in subsequent years, I have found the results extremely variable, — not more than one or two sometimes recovering, out of a large number that had been dried up. It is interesting to remark, that, whilst, in the embryo which is being developed from the egg, the rotatory and masticating organs are the first parts which exhibit motion, they are the last to revive after this kind of resuscitation. 932. We observe, then, in the Rotifer vulgaris, a very manifest 324 WHEEL-ANIMALCTJLES ; — HYDATINA. tendency to the Vermiform character, exhibited in the elongated shape of the body, the position of the eyes and mouth at one extremity of it, the narrow, straight, intestinal canal having its second orifice near the other extremity, and the mode of locomotion when the tail is detached and the operation of the wheels suspended. This tendency, however, is not so marked in some species of the class, which are in many respects more high- ly developed than this ; — for example, the Hydatina senta, an animalcule not uncommon in vegetable infusions. Here the body is somewhat funnel- shaped ; and the cilia are arranged around the wide mouth, in two con- centric rows. The outer row consists of a simple continuous circle arranged upon the edge of the body ; but the inner one is made up of eleven groups of cilia, attached to distinct muscular lobes. The integument appears to consist, as in the Rotifer, of two membranes, both of which are soft and flexible. To the inner one are attached four pairs of longitudinal muscles, by which the chief movements of the body are performed. The tail has separate muscles for its retraction or protrusion ; and others are seen at the large extremity of the body, which fold up the ciliary apparatus. The mouth is situated in the centre of the large extremity of the body ; it leads, through a short oesophagus, to the first stomach or gizzard, the jaws at whose entrance are pro- vided with five or six pairs of teeth. Into this cavity a pair of secreting ca3ca open ; and between the termination of these is the commencement of the intestinal tube ; the upper part of which, being very distensible, may perhaps be regarded as a second stomach, since in this the digestive process is principally performed. The intestine terminates, as in the Rotifer, near the FIG. 638. — HYDATINA SENTA ; a rows of cilia ; b, muscles of the jaws ; c, stomach ; d, enlarged ter- mination of the intestine ; e, anus ; /, salivary glands ; g, ovaria ; h, dorsal vessel. STRUCTURE AND REPRODUCTION OF HYDATINA. 325 posterior part of the body ; and the oviducts open into the dis- tended extremity of its tube. The nervous system is here easy to be distinguished. It consists of a kind of circle surrounding the oesophagus, on which three pairs of ganglia may be observed. From the lower pair there proceeds a double cord, which passes along the ventral surface of the body to its opposite extremity. 933. The reproductive powers of the Hydatina are very remark- able. The number of eggs contained in the ovarium at once is never large, seldom exceeding three or four ; but they are frequently deposited and renewed, and themselves soon arrive at maturity. The following experiment is related by Ehrenberg : — " On Nov. 21, I placed in a jar a young Hydatina containing an egg nearly mature. I added for its food a drop of liquor containing Monads. On the morning of the 22nd, the egg had been deposited. On the 23rd I met with four individuals, of which two were fully developed. On the morning of the 24th, there were twenty. The observation ceased at this point ; as it became too difficult to count the numbers which thus rapidly increased. In a space of 72 hours, twenty individuals had been formed — one only having been employed as the stock ; and at this rate of increase, the numbers would be, at the end of ten days, 1,048,576 ; and this number would be quadrupled in another day. Even if only two instead of four were produced daily by each individual, a million would be called into existence in twenty days ; and on the twenty-fourth day, we should have 16,777,216 animalcules." When we consider, in connection with this rapid increase in number, the curious power of revivification possessed by these beings, it is obvious that we need not have recourse to the idea of spontaneous generation,* to account for their sudder* appearance in various situations, and for their speedy multiplica* tion, wherever the conditions, in regard to food, temperature, &c., are favourable. * This term refers to an idea, which has been entertained at various times, that animals of low organization may of themselves originate, by the accidental meeting of particles adapted to form their structure. VOL. II. A A CHAPTER XIV. OF THE MOLLUSCA. IN GENERAL. 934. QUITTING now the Articulated series, — which we have seen to terminate in very simple forms of structure, that lead us towards the Zoophytes, — we return to a higher point in the Animal scale, to descend in like manner through the Molluscous series. Looking only at the general complexity of structure exhibited by these groups of Animals respectively, we might have some difficulty in deciding which should rank the highest ; since in the Articulata we observe one set of organs far more highly organised than in any of the Mollusca ; whilst the converse holds good as to another set of organs in the Mollusca. But when we look at the respective characters of these organs, we cannot reasonably hesitate longer. It is the organs of animal life that are so highly developed in the ARTICULATA ; whilst it is in the development of the organs of nutritive or vegetative life only, that they are surpassed by the MOLLUSCA. In the Animal scale, therefore, we may justly regard the Articulata as ranking on the whole above the Mollusca. To the consideration of the latter group we shall now proceed. 935. The range of animal forms comprehended in the sub- kingdom MOLLUSCA is so great, that it would be difficult to include them by any character common to all. We encounter but few traces of the circular disposition of organs around the mouth, which is characteristic of the Radiated tribes ; and we seldom meet with any thing that even approaches to the elon- gation of the body, still less to the division into segments, which has been noticed among the Articulata. This will be compre- hended, when it is borne in mind that the body of the Mollusca is almost entirely occupied by the organs of nutrition ; and that the organs of sensation and locomotion are entirely subservient to GENERAL CHARACTERS OF MOLLUSCA. 327 the supply of these. "We find in the lowest tribes of this group, living beings which are fixed to one spot during all but the earliest period of their lives ; and which scarcely possess within themselves so much power of movement, as that enjoyed by the individual polypes in a mass of Coral ; and yet these exhibit a complex and powerful digestive apparatus, a regular circulation of blood, and an active respiration. But we nowhere find, throughout the whole animal kingdom, that the conformation of these organs governs the shape of the body ; they rather adapt themselves to the type which predominates in its structure, and which is principally manifested in the disposition of the loco- motive organs. Thus, the stomach of the Star-fish sends a prolongation into each ray; whilst in the Articulata, on the other hand, we find the digestive cavity prolonged into a tube, in accordance with the form which the body there possesses. 936. Thus we see that, in regard to external shape and arrangement, the apparatus of Organic life has no definite plan of its own ; and in the Mollusca there is an absence of any general type, to which it may be made conformable. Hence the shape of the body varies extremely in those classes, in which it is entirely or principally composed of these organs; and no general character can be given, which shall apply to all, or even a large part, of the animals composing them. There is often an entire want of every kind of symmetry ; that equality of the two sides, which is peculiarly characteristic of the higher animal^ being deficient ; as well as the radial arrangement of parts seen in the lower. But this is only the case, where there is no development of a head ; that is, of a prominent part on which the mouth is situated, and which also bears the organs of sensa- tion, if any exist. In the higher Mollusca, which possess not only sensory tentacula, but eyes, and even organs of smell and hearing, we find these disposed in a symmetrical manner ; so that the head (where it exists), or the part peculiarly concerned in animal life, presents a bi-lateral equality of parts, even where the remainder of the body wants it. In the more active species among the higher classes, we find this bi-lateral symmetry extending in many instances through the whole body ; evidently 328 GENERAL CHARACTERS OF MOLLTTSCA. bearing a pretty close relation with the degree of locomotive power. It is most evident and complete in the CEPHALOPODA ; many of the animals in which class are adapted to lead the life of Fishes, and resemble them in the general form of the body and in the structure of many individual organs. 937. As a group, however, the MOLLUSCA are to be characterised rather by the absence, than by the possession, of a definite form ; and there is a corresponding absence of any regular organs of support, by which such a form could be main- tained. The name they have received designates them as soft animals ; and this they are pre-eminently. The Shell, where it exists, is to be regarded rather in the light of an appendage designed for the mere protection of the body, and deriving its shape from it ; than as a skeleton, giving attachment to muscles, and regulating the form of the whole structure. Where the body is entirely inclosed within it, as in the lower bivalve Mollusca, no locomotive powers whatever, except such as depend on the passage of water through the respiratory tubes, are enjoyed by the animal. It is only where the body is uncovered by a shell, or a portion of the body can be projected beyond it, that any active movements can be executed ; and the muscles concerned in the performance of these do not make the shell a fixed point, as is done by those of Articulated or Vertebrated animals in regard to their skeletons, but are entirely unconnected with it. 938. Hence we see that the shell of a Mollusk is, when considered in reference to its functions, a very different organ from that of a Crustaceous animal, although formed in somewhat the same manner. Its frequent absence might of itself lead us to suspect its want of importance to the living structure. In one whole class of Mollusca it is entirely deficient ; and in three others it is frequently absent. In only two it is universally present. When speaking of the anatomical conformation of the body, therefore, we may leave the shell pretty much out of considera- tion. Before the animals which produce them had been properly studied, Naturalists founded their classification of Mollusca upon the shells only ; and the greatest confusion thus resulted. Shells GENERAL CHARACTERS OP MOLLUSCA. 329 of very similar aspect are often produced by animals extremely unlike each other,* and living in different conditions — as, for instance, fresh and sea water. And shells of very dissimilar character in the eye of the mere Conchologist, often belong to animals closely allied. In fact, the form of the shell taken alone is a character as purely artificial, as the number of stamens and pistils in a flower ; and will lead to a classification as far removed from a natural plan. But when the principal divisions have been formed upon other grounds, the conformation of the shell will often afford valuable subordinate characters ; and the Naturalist seeks to employ these as much as he safely can, on account of the facility with which he can apply them to the study of those fossil remains, from which all traces of the animal itself have disappeared. The softness of the entire body of the Mol- lusca prevents us from recognising its form and structure after death, in any other way than by the shell ; but upon this, it must be remembered, entire reliance cannot be placed, since it is liable to great variation, in accordance with the circumstances of the individual, whilst it is by no means certain that there are constant differences in its form in distinct species. 939. The only tribe of Mollusca which presents anything that corresponds to the internal skeleton of the Vertebrata, is that of the Cuttle-fish. There is in their bodies a cartilage, partly inclosing the nervous centres in the head, and sending prolongations along the back, for the protection of the large nervous cords which traverse it, and for the attachment of the muscles by which it is mored. These last are especially deve- loped, where the body is spread out into fin-like processes, re- sembling those of Fishes, by the stroke of which active move- ments are produced (Fig. 640). This skeleton is almost as highly organised as are the lowest forms of that internal skeleton which is characteristic of Vertebrata (§ 639). 940. In all the Mollusca, the soft body of the animal is * The impossibility of founding a correct classification upon the characters afforded by the shell only, is made at once apparent by comparing the shell of a Serpula (Fig. 629) with that of a Vermetus (Fig. 672). Between these two shells there is no essential difference ; yet the animals which form them belong, not merely to different families, but to different sub-kingdoms. 330 MANTLE AND SHELL OF MOLLUSCA. inclosed in a spongy elastic skin, with which muscular fibres are interwoven ; this is termed the mantle. This envelope is fre- quently not applied closely to the surface of the organs contained in it ; especially among the lower classes, in which the space thus left constitutes a respiratory chamber. It has apertures for the admission and exit of the surrounding water, to effect the aeration of the blood ; and, when the mouth is not capable of being projected beyond it, the same current furnishes the supply of food. These apertures are sometimes extended, for particular purposes, into proboscis-like tubes (Fig. 697). Where the head is capable of being protruded, there is usually an opening in the mantle for the purpose ; and another for the foot, where it exists as a separate organ. 941. The mantle is chiefly interesting, as being the portion of the body alone concerned in the formation of the shell. Some- times this envelope is secreted from nearly the whole surface ; sometimes from only a small part of it. As the same general statements in regard to the constitution of this body will apply to all the Mollusca, its origin and essential characters may advantageously be described, previously to the more detailed account, which will be given of the several classes, in which its leading peculiarities of form will be noticed as they occnr. Shells are formed, like bones, of a combination of earthy and animal matter. The former consists entirely of carbonate of lime, which is usually deposited in a crystalline condition. The latter is composed of layers of membrane, alternating with the mineral matter; and of cells inclosing it. The cellular structure, which seems to be of the nature of Epithelium (ANIM. PHYSIOL. § 39), is generally found upon the surface. If the carbonate of lime be removed by the slow action of a weak acid, the animal matter will remain, sometimes in the form of a continuous membrane, but sometimes only as a flaky mass, easily shaken into separate portions. The shell is most solid and massive in those species which lead an inactive life ; and it attains greater weight in the Conchifera, in which every species forms a stony covering, than in the Gasteropoda, whose powers of locomotion are somewhat greater, and in which the shell is often absent, FORMATION OP SHELL OF MOLLUSCA. 331 and is frequently composed, where it does exist, of nothing but a thin horny plate, destitute of calcareous deposit. 942. As the mouth of the shell is always at its widest part, and as, in extending it, the cavity is enlarged as well as its entrance, there is evidently no necessity for such a division into separate plates, with a provision for the individual growth of each, as we have seen in the Cirrhopoda (§ 897) ; nor for the periodical exuviation and renewal which is performed by the Crustacea. In order to adapt its size to the progressive increase in the bulk of the tody, new layers are deposited from the mantle at intervals, each of which usually lines the previous one, and extends beyond it. The portion which thus projects is generally thicker and firmer than the rest of the new layer ; since that part which is deposited within the previous layers is protected and supported by them. And the corresponding part of the mantle is also thicker and more spongy, so as to possess almost a glan- dular texture. At this part of it, indeed, are situated the glands, by which the colouring matter is secreted, that gives to the exterior of the shell its beautiful and variegated tints ; these are wanting in that portion of the mantle, which merely forms the lining to the older layers. In general we find each new layer in immediate apposition with the last ; but this is not always the case. The animal forms it upon the mould, as it were, of its own body ; and if this has shrunk, or changed its form, so as not to occupy the whole cavity of the shell, a space will inter- vene. This is remarkably shown in the Spondylus varius, or Water- Clam, a section of whose shell exhibits a regular series of chambers thus formed ; and these are usually filled with water. In the common Oyster such spaces may often be ob- served ; but they possess no regularity. The animal always appears inclined to adapt its shell to the form of the body, by reducing its cavity if necessary, as well as by extending it ; and thus an Oyster, which has been kept without food, and whose body has thereby shrunk, so as not to fill the interior of the shell, will expend its last energies in forming a new layer adapting the interior surface to its altered condition. The texture of the shell varies considerably in the different tribes of 332 LOCOMOTION OF MOLLUSCA. Mollusks ; and it often furnishes characters in classification, which are equally useful with those derived from its form. 943. The means of locomotion possessed by Mollusca are usually very limited ; and the absence of any constant and regular provision for this function, is an additional evidence how little it enters into the general plan of the group. "We have seen in the Articulated series, that, wherever members or instru- ments for locomotion exist at all, they have the same character and situation, — being developed from the several segments of the body, with more or less complete uniformity. Now among the lowest Mollusca we shall find, that some tribes are entirely fixed, during all but the earliest period of their lives ; that in others, although the body is not fixed, it has no other means of movement than that afforded by the respiratory currents, which cause it to advance gently through the water, without (as it would appear) any voluntary control on its own part. In many animals inhabiting Bivalve shells (i. e. Shells which are formed of two parts or valves, united by a hinge) there exists what is termed a foot ; which is nothing else than a fleshy tongue-like projection, sometimes enabling the animal to leap upon hard surfaces, sometimes used as a boring apparatus, sometimes em- ployed as a sort of fin for swimming, and sometimes chiefly useful as the instrument for producing the byssus, a sort of cord by which the animal attaches itself to rocks, &c. — In the animals inhabiting the greater number of Univalve shells, there is no such projecting foot ; but the under side of the mantle is thick- ened into a fleshy disc, which, by its contractions and expansions, serves as an instrument of progression. This is well seen in the common Snail. Among the animals allied to these in structure, but not possessing a shell, the whole mantle is muscular ; and by the contractions and expansions of its different parts, the general movement of the body is effected. This is especially the case with the aquatic species of this group ; some of which are thus enabled to swim with considerable rapidity. — Again, in the Mollusca of the Cuttle-fish tribe, we find this method replaced by others, which are more efficient, but which are entirely different in their character. This group 13 Distinguished ORGANS OP LOCOMOTION AND SENSATION. 333 by the presence of a set of arms or members disposed in a cir- cular or radiating manner around tbe mouth ; and these arms are frequently the chief instruments of locomotion, as well as of the prehension of food, being furnished with a strong connecting membrane, that forms a sort of circular fin, by the aid of which the animal swims backwards (Fig. 645). In other members of this group, the arms are less developed, but the body is elon- gated into a fish-like form ; and it is furnished at its edges with fins much resembling the dorsal and anal fins of Fishes, and supported by the cartilaginous internal skeleton already men- tioned (Fig. 640). From this general sketch it is evident that the appendages for locomotion do not possess, in the Molluscous series, anything like the same regularity of development which they manifest in the two preceding ; and that locomotion forms a much smaller part of the life they are destined to lead. In fact, the word sluggish^ which is founded upon the well-known habits of a naked (or shell-less) terrestrial Mollusk, very well expresses the general character of the group in this respect. 944. The amount of development of the organs of sense in Mollusca, varies as much as the character of the locomotive apparatus. Thus in the highest class, comprehending the Cuttle- fish and its allies, the head is furnished with a pair of large well- formed eyes, constructed upon the same general plan as those of Vertebrata. There is also an apparatus for Hearing, much resembling that which exists among the lowest Fishes ; and there is reason to believe that an organ of Smell is also present. The senses of Taste and Touch appear to be very acute. It is in such animals that we should expect to find the organs of sensation most developed, on account of their rapid locomotion and voracious habits. In the Gasteropods, which are not so much distinguished in these respects, we find the organs of sense less developed ; but it is seldom that either of them is altogether absent.* Descending lower, however, we no longer find these organs situated upon a prominent part of the body ; nor are they usually placed in the near neighbourhood of the mouth. This * An apparatus for hearing, though of a very simple kind, has been detect- ed in a large number of this class. 334 NERVOUS SYSTEM OF MOLLUSCA. is usually furnished, indeed, with feelers or tentacula, which are nothing else than prolonged lips, and which serve to distinguish and select the food ; but the eyes, if any are present, are gene- rally placed elsewhere, in such a position as to be of the most effectual guidance in the movements of the body. In the lowest Mollusca, we lose all traces of any special organs of sense ; and it appears as if the sense of feeling, possessed in all probability by the body in general, but peculiarly by the lips or tentacula, is the only one through which the animal can receive any inform- ation of its condition. 945. The conformation of the Nervous System is very much what might be anticipated from the facts just stated. It by no means displays the same complexity, or seems to possess the same importance as a prominent feature in the composition of a Molluscous, as it does in that of an Articulated animal ; and its arrangement is not marked by any regular characters, but varies with the disposition of the organs with which it is connected. Thus we have a single ganglion, or a pair of ganglia, situated in the head, where this exists as a distinct part ; and these ganglia, which seem to be the principal seat of the instincts of the animal, serve to direct those movements which are not reflex. The gills, the pharynx, the foot, and other organs, usually have their own distinct ganglia ; and these, which are all connected with the cephalic ganglia (those situated in the head), seem to be the centres of the reflex actions of the several parts (AwiM. PHYSIOL. § 439, and ZOOLOGY, § 53, and Figs. 35 and 36). In the lowest Mollusca we find but a single ganglion, which seems in some degree to combine all the functions just mentioned, but to be particularly connected with the respiratory apparatus. 946. The Mollusca are, for the most part, extremely vora- cious ; and are not particular in their selection of food. It is in those which possess most power of locomotion, that we see (as might be expected) the greatest exercise of choice ; those which are dependent for their aliment upon the casual supplies brought by the sea, being obliged to take what they can thus get. Their digestive apparatus is always highly developed, We uniformly meet with a large liver ; and frequently with salivary CIRCULATION AND RESPIRATION OF MOLLUSCA. 335 glands, and organs of mastication. There is frequently a com- plete gizzard, or muscular stomach, for the reduction of the food, when this is not accomplished in the mouth ; and the intestinal tube is often of considerable length, and much convo- luted, or rolled together. The blood is colourless or nearly so ; and circulates, in all Mollusks, in a regular system of arteries and veins, issuing from a heart, which is usually muscular or nearly so, and possessed of two cavities, one of them a receiving cavity or auricle, and the other an impelling cavity, or ventricle (ANIM. PHYSIOL. § 257). The accompanying figure will give an idea of the usual mode in which the Circula- tion is carried on in this sub- kingdom. The blood (which has returned from the gills in an aerated state) is pro- pelled, by the ventricle, «, through the main systemic artery, b ; after passing through the capillaries of the system, it is collected by the systemic veins, /, into a large trunk, which again subdivides into the branchial arteries, g\ these convey the blood, now ren- dered VenOUS, to the gills, £, * . . . Where it IS aerated ; and after returning thence by the branchial veins, 6?, it enters the auricle, c, whence it passes again into the ventricle, a. — The Respiration of Mollusks is almost always aquatic ; being carried on by the aid of gills, which expose a large surface of blood to the water at once. These gills are sometimes altogether exterior to the body (Fig. 679) ; sometimes they are enclosed between folds of the mantle (Fig. 674) ; and sometimes the respiratory surface is altogether internal. In this d, ventricle ; ft, main artery or aorta ; c, auri- cle; Abranchial veins ; e, vessels of the gills; /, systemic veins ; g, branchial arteries ; h, tentacuia. 336 CLASSIFICATION OF MOLLUSC A. last case it may be so disposed as to admit the flow of water introduced from without over its surface, as we shall see among the Tunicated Mollusks ; or it may be adapted to expose the blood to the influence of air, as is the case among the Terrestrial Gasteropods (the Snail, Slug, and their allies), which are the only Mollusca not aquatic. 947. In the classification of the Mollusca, the system of Lamarck will be generally followed, with some modifications rendered necessary by the researches of others. The Sub- Kingdom may be first divided, like that of Articulata, into two principal sections ; — the first including all those which have a distinct head, or (in other words) which have the mouth situated on a prominent part of the body, furnished with organs of special sense ; — the second comprehending those in which no such head exists, the mouth not being capable of being projected beyond the body, and no organs of special sense being present. The former may be termed Cephalous, and the latter Acephalous (or headless) Mollusks. The Cephalous Mollusks are usually divided into the three following classes : — I. CEPHALOPODA, which have feet or tentacula arranged in a circular manner around the head, as in the Cuttle-Jlsh tribe. In this group we find the nearest approach to the Vertebrata. II. PTEROPODA, a small but interesting class, characterised by the possession of a pair of wing-like expansions of the mantle, which serve as fins, and enable them to swim with great velocity. III. GASTEROPODA, the most extensive group of the Sub-King- dom, have a single foot, or muscular disc for locomotion, formed by a thickening of the mantle on the under surface of the body. The animals of the two preceding classes are entirely marine ; there are species among these which live in fresh water, and even on land. With the Gasteropoda we also place the aberrant group of HETEROPODA, which has been regarded by many authors as forming a distinct class. The animals composing it are especially distinguished by the form of the foot ; which, instead of being a horizontal disc, is compressed vertically, so as to form a fin, which is turned upwards, instead of being situated below the body. 948. In each of the foregoing Classes, we observe a consider- able variation in regard to the relative size, and even the very CLASSIFICATION OF MOLLUSCA. 337 existence, of the Shell ; for, whilst there are some species in all of them which are entirely destitute of this protection (such being called naked Mollusks), there are others which possess it in a slight degree, having it generally concealed in a fold of the mantle ; whilst in others, again, it completely envelopes the body when they desire to withdraw themselves under its protection. In nearly every case, the Shell, where it exists, is Univalve. — In the Acephalous Mollusks, we find two distinct groups ; in the first of which the shell is always present ; whilst in the second it is invariably absent. The first is therefore named Conchiferous, or shell-bearing ; and the latter Tunicated, — the shell being replaced by a leathery or membranous tunic. The Conchiferous Acephala, with scarcely an exception, have Bivalve shells ; and they are again divided into two classes, according to the arrange- ment of their respiratory organs. IV. LAMELLIBRANCHIATA, having the gills arranged in four lamellce, or riband-shaped folds, which run parallel to the edges of the shell. To this group belong all the ordinary Bivalves. V. PALLIOBRANCHIATA, having the respiratory surface formed by the mantle itself. The animals of these shells differ in several other important particulars from the preceding. This class is very small at present, in comparison with the other Bivalves ; but in the more ancient periods of the earth's history, a very large proportion of the Bivalve Mollusks seems to have belonged to it. VI. TUNICATA, a group including all those Acephalous Mol- lusks which are destitute of a shell. In this class we find many points of structure which lead us towards the Zoophytes. The Tunicata really differ in many important particulars from most of the other Mollusca, especially in the very slight development of the nervous system, which consists of a single ganglion, situ- ated in the vicinity of the oesophagus, and giving off nerves in vari- ous directions. In this respect, they agree with a curious group until recently placed amongst the Zoophytes, but which are now proved to belong to the Mollusks, of which they form a seventh class. VII. POLYZOA, a group of minute compound animals, each residing in a distinct cell, and furnished with ciliated tentacles surrounding the mouth. The Polyzoa and Tunicata form the subdivision Molluscoida of some authors. 338 CHAPTER XV. OF THE CLASS OF CEPHALOPODA. 949. THE Cephalopoda unquestionably constitute the group of highest organisation in the Molluscous sub-kingdom. They are characterised by the possession of feet, or locomotive organs, around the head ; whence their name is derived. But these feet have no analogy either with the fleshy disc of the Gasteropods, or with the feet of Articulata or Vertebrata. They are, in fact, prolonged tentacula, or lips. In the Nautilus (Fig. 648), which approaches the nearest to Gasteropoda, they are very numerous, and are evidently feeble as instruments of prehension ; whilst they would seem, from the distribution of their nerves, to be more concerned in sensation. In some of the Cephalopoda the feet are much prolonged, and of great power ; and are evidently very important organs both of locomotion and prehension (Fig. 643). But in those forms which approach most nearly to Fishes, we find them again greatly reduced in size, in propor- tion to the elongation of the body ; and it is by the latter, and the fin-like expansions with which it is provided, that progression is then chiefly accomplished (Fig. 640). FIG. 640.-CALAKAKY. possess tentacular prolong- ations of the lips, evidently analogous to the arms of the Cepha- lopoda ; and this is one of the many interesting points by which a transition is effected between these two classes. In many species of this class one of the arms of the male is singularly modified and rendered subordinate to the business of reproduc- tion ; in the Argonaut and Tremoctopus, this arm is even thrown off by its owner, when it attaches itself to the female, and exhi- bits so much vitality that it was until recently described as a parasitic worm, under the name of Hectocotylus. The Nautilus is the only one amongst existing Cephalopoda, in which the prin- GENERAL CHARACTERS OP CEPHALOPODA. 339 cipal part of the body is contained within a shell. Animals of this kind were formerly much more abundant. At present the naked species, as they are termed — in which the shell is rudi- mentary, and is inclosed between folds of the mantle instead of being external to the body — are the chief inhabitants of our seas. In some of these, the shell still retains considerable size and density, as the common pounce-bone ; but in the long slender species, which swim by the movements of the whole body, it is necessarily flexible ; and here we find it very narrow, and com- posed of a light horny substance, so as to bear some resemblance to a feather. 950. The trunk of these animals is inclosed in the mantle ; which is shaped like a bag, sometimes nearly spherical, some- times more or less elongated ; inclosing all the viscera, and < being only open in front (Fig. 641, o). The head, projecting from this opening, is round, and generally provided with two large eyes, of a struc- ture very similar to those of Vertebrated animals. The mouth is situated in the centre of the circle of arms ; and is armed with a pair of horny mandibles, which have very much the form of the Parrot's beak — The arms are sometimes all of equal length, as in the Octopus (Fig. 645) ; and sometimes two are much longer than the rest, as in the Calamary. — Cephalopoda are essentially aquatic, and breathe therefore by gills. These organs are concealed beneath the mantle in a particular cavity (Fig. 641), tne wans 01 waich dilate and contract alternately, and which communicates with FIG. 641 — GILLS OK Potxr. 340 RESPIRATION AND CIRCULATION OF CEPHALOPODA. the exterior by two openings — one like a slit (o) for the entrance of the water — the other, for the exit of water and excrements, formed like a tube or funnel (£). By the forcible expulsion of the water through this funnel, most of the Cephalopoda are able to swim, tail foremost, with considerable rapidity. Each gill (b) is shaped like a prolonged pyramid ; and is composed of a great number of membranous lamella?, placed transversely, and fixed on both sides of a central stalk. The number of gills varies ; and this difference is characteristic of two great divisions, of which this Class is composed. In the Poulp, Cuttle-fish, and Calamary, there exists but a single pair ; whilst in the Nautilus there are two. 951. The heart is situated between the gills, on the median line of the body, and is composed of a single ventricle only (c, Fig. 642). The blood from the gills flows into this ventricle tt> oc a et w FIG. 642.— ORGANS' OP CIRCULATION AXU RESPIRATION IN CUTTLE-FISH. by branchial veins (vb\ whose openings are provided with valves : it then enters the arteries (as, b), which spring from this organ, and is distributed into the body. This liquid then returns into a large vena cava (vc) ; which, when arrived near the heart, divides itself into two branches (ab) to enter the gills ; lastly RESPIRATION AND DIGESTIVE APPARATUS. 341 these vessels, when arrived at the base of the respiratory organs, generally present remarkable dilatations (cb\ interwoven with muscular fibres, so as to form two contractile reservoirs, perform- ing the functions of pulmonary hearts. This arrangement is observable in all CepTialopods with two gills ; but does not exist in those which are provided with four. It may be regarded as a transition-form between the heart of the lower Mollusca, which is altogether systemic (§ 946) ; and that of Fishes, which is en- tirely respiratory (§ 555). 952. The digestive apparatus is very complicated. The mouth is surrounded by a circular lip ; and the parrot-like jaws are put in motion by powerful muscles. There are well-developed salivary glands, several stomachs, and a voluminous liver ; the intestine terminates in the branchial cavity, at the base of the funnel by which the water is ejected, and communicates with a very singular secreting organ, which, in the dibranchiate (two- gilled) Cephalopods, produces an abundance of a black liquor, commonly termed its ink. The duct of this gland opens near the anus ; and, when the ani- mal is in danger, it expels this liquid through the funnel in sufficient quantities to hide it from the view of its enemies, by mingling with the surrounding water. It is the ink of one of these animals, the Cuttle-fish, which is employed in paint- ing, under the name of Sepia ; and several authors look upon Indian Ink as an analogous sub- stance. The four-gilledCephalo- podspresentnothingofthiskind. 953. The arrangement of the organs of locomotion, which are fixed around the mouth, varies in different divisions. In the two-gilled Cephalopods, there is a crown of large fleshy tenta- cula, whose internal surface is provided with suckers, by means of VOL. II. B B 34'2 NERVOUS SYSTEM OF CEPHALOPODA, which the animal fixes itself with great force to any body which it embraces. In the Poulp we find eight of these appendages, and in the Cuttle-fish ten. Sometimes two of them are expatidea into flattened mem- . branes, as in the Ar- gonaut (Fig. 646) ; or are elongated so as to become filiform^ or threadlike, as in the Calamary, and particularly in the Loligopsis (Fig. 643). In the four- gilled Cephalopods these appendages are quite slender, and unprovided with suckers; but they are extremely nu- merous (Fig. 648). 954. Most Mol- lusca of this class are remarkable for the development and perfection of their eyes, which are ex- ceedingly like those of Yertebrated ani- mals. Many possess also an apparatus for Hearing ; but this organ is reduced to a little membra- nous sac repre- senting the vesti- bule, and receiving a nerve (ANIMAL PHYSIOL. § 512). FIG. 644. — a, nervous collar embracing the oesophagus, the passage of which is marked by the bristle * ; c, ner- vous mass, apparently analogous to the Cerebrum of Vertebrata, from whose under side proceed connecting cords to two ganglia situated in front, which send nerves to the mouth, lips, pharynx, &c. ; ft, tentacular ganglia, sending nerves to the arms ; o, optic nerves ; g, sub-ceso- phageal ganglion ; v, great nerve of the viscera, of which one of the branches possesses an elongated ganglion, r, and enters the gills ; m, another branch, having the same origin, and furnished with a star-shaped ganglion, e, that sends nerves to the mantle. Lastly, the nervous system of these aninmls NERVOUS SYSTEM AND LOCOMOTION OF CEPHALOPODA. 343 is more complicated than that of other Mollusks; and the different ganglia, situated around the oesophagus, tend more to unite in a single mass. The nervous collar thus formed is composed of a pair of cephalic ganglia, whence originate the optic nerves ; of a pair of ganglia, situated more in front, but beneath the oesopha- gus, and furnishing the tentacula with nerves ; lastly, of a pair of thoracic ganglia, supplying the mantle with nerves, and sending backwards two cords on' each side, which are themselves furnished with ganglia, whence proceed nerves that supply the mantle, gills, heart, &c. It is evident from this description, that the nervous system of the Cephalopods approaches that of the lower Fishes in many particulars ; especially in the almost complete concentration of the nervous centres in the region of the head, and in the presence of the rudiments of a cerebral mass. If the cords that proceed backwards from the sub-oasophageal ganglion had been united on the central line, instead of diverging from each other, they would have presented a strong analogy in position, as well as in function, to the Spinal Cord of Yertebrata. 955. Cephalopods are almost exclusively marine in their habits ; only a few of them, such as the Octopus or Poulp (Fig. 645), ever quitting the water to prowl along the shore in search of food. When thus moving, they walk in what may be considered an inverted position ; the mouth being downwards, and the opposite extremity of the body being directed upwards. When swimming, the Poulp moves backwards through the water, propelling itself by the alternate contractions and exten- sions of the circular fin, which unites the bases of the arms. But the long slender-bodied Calamaries (Fig. 640), in which the arms are short, swim much more after the manner of Fishes ; striking the water, by means of the fin-like expansions of the mantle along the back and abdomen, with such force as occasionally to raise themselves out of the water. The Nautilus (Fig. 648) seems more limited in regard to its means of locomotion ; since its arms are not long enough to serve as efficient instruments for this purpose, and it has no other means, except a fleshy disc, which resembles that of the Gasteropods, and which enables the animal to crawl along solid surfaces in an inverted position. 344 HABITS OF CEPHALOPODS. 956. The animals of this Class are extremely voracious in their habits ; and seldom, if ever, devour anything but animal food. They chiefly prey upon small Fishes and Crustacea ; and seem especially destined to restrain the too rapid multiplication of the latter. Winding its arms around the body and limbs of even a powerful Crab, and securing them all by fixing its suckers upon their surfaces, the Cuttle-fish can pick the shell to pieces with its powerful mandibles, and extract the contained flesh, without fear of injury; — an action which no animal of any other Class could attempt. The firm armour, and powerful crushing jaws, of the more ancient Fishes, might have enabled them likewise to feed upon Crustacea; but no such Fishes now exist. The Common Cuttle-fish, and the Calamaries or Squids, are often very troublesome to fishermen, by following shoals of fish into the nets, devouring large quantities of them, and 'watch- ing an opportunity to dart away before they can themselves be seized. In their turn, they become the prey of the larger Fish and of Cetacea. They are much used as baits in the Newfound- land Cod Fishery ; and in the stomachs of the smaller Cetacea great numbers of the undigested horny Mandibles are frequently found, indicating (of course) that at least a corresponding num- ber of the Cuttle-fish have been devoured by them. — Some species of this class attain a considerable size. The Onychoteuthis, the suckers on whose two long arms are furnished with hooks at their edges, has been known to attain the length of six feet ; and it is much dreaded by the natives of the Polynesian islands, who are said to have been attacked by it, when diving for shell-fish. 957. The Class of Cephalopoda may be divided into two Orders, according to the number of the gills (§ 950); — the DIBRANCHIATA, or two-ffilled, including the Cuttle-fish, Argo- naut, and their allies, having only one pair of those organs ; — and the TETRABRANCHIATA, or four-gilled, including only the true Nautilus among the existing Cephalopods, but comprehend- ing a vast number of species now extinct, possessing four of those organs. The latter of these Orders is the one most allied to the Gasteropoda, both in the structure of the shell, and in the conformation of the animal. ORDER I.— DIBRANCHIATA. 958. The species of the Dibranchiate Order are extremely numerous ; and they frequent every part of the ocean, from the arctic to the equatorial regions, some preferring the neighbour- hood of the shores, whilst others are found only in the open sea. None of them possess more than ten arms, and a part have only eight ; the latter are considered as forming the highest group, being the most removed from the Tetrabranchiate Order. In only one genus, the Argonauta, do we find the body inclosed in an external shell ; in all the rest, the shell, or that which repre- sents it, is internal, or rather is included between two folds of the mantle ; and it serves rather as an organ of support, than as a protection to the animal. 959. The Octopod, or eight-footed section of the Order, includes two families, — the OCTOPODID^E, or Poulps, and the ARGONAUTI- IXE, or Argonauts. In the former the body is naked, the internal shell is rudimentary, and none of the arms are expanded at the apex into broad webs. To this family belongs the com- Fio. 645.— OCTOPUS OB POULP. mon Octopus or Poulp (Fig. 645), which is abundant on the southern coasts of Europe, and is occasionally met with on our own shores. This animal is the Polypus of ancient 346 OCTOPUS OR POULP. Naturalists ; who were quite unacquainted with the animals to which the name is now restricted. (Indeed this name was first conferred on the Hydra and its allies, on account of their simi- larity in form, and in the position of their prehensile arms OP feet, to the animal previously known under that appellation.) The common Poulp has arms six times the length of its body ; and each of these is furnished with 120 pairs of suckers. Every sucker is composed of a circular adhesive disc composed of a muscular membrane ; this has a thick fleshy circumference, and presents a number of lines radiating towards the circular orifice of an inner cavity, situated beneath the central part of the disc. In this cavity is a moveable circular piston ; which, when the sucker is not in action, appears level with the circular aperture; but which, when the disc is closely applied to any object, is strongly drawn back, so as to increase the size of the cavity and produce a vacuum in it ; — forming, in fact, an air-pump of the most precise and beautiful construction. When the animal releases its hold, it relaxes the muscles that drew back the piston ; and the vacuum is then made to cease. The whole apparatus might be compared to a boy's leather-sucker, with an exhausting syringe fitted to its centre. 960. It may be noticed, as a curious example of reflex action, that the nervous trunk supplying each arm of the Octopus, is furnished with a series of ganglia, corresponding in number and position with the suckers. A part of the trunk passes over the whole series of ganglia without entering them, — precisely as in the case of the ventral cord of the Articulata (ANIM. PHYSIOL. § 442) ; and this sends branches into each sucker, so as directly to convey to them the influence of the cephalic ganglia, and thus to cause them all to contract at the will of the animal. On the other hand, each sucker receives nervous filaments from its own ganglion ; and may be made to contract, when stimulated to do so, by the contact of a solid substance, even though the arm is entirely separated from the body. Hence, when a Cuttle-fish has fixed itself upon any animal, it may be cut into pieces with- out the suckers relaxing their hold ; since the muscles of every sucker are called into action by the reflex properties of its own OCTOPUS OR PODLP.— ARGONAUT. 347 ganglion alone. The conformation now described is common to the whole Order. 961. In regard to the Poulp it has been justly remarked, that " there is something strange and uncouth in the aspect of this creature ; its long flexible arms moving and curling in all directions ; and its large eyes, which stare with fixed gaze, rendering it even repulsive." Even a cursory observer would pre- dict it to be ferocious and carnivorous ; and its actual character harmonises with its appearance. Woe to the Fish that is infolded within the tenacious grasp of its arms. Resistance is vain ; for the suckers adhere with such tenacity, that they may sooner be wrenched off than unfixed. Closer and closer to the mouth is the victim brought ; until, being firmly secured as in a vice, the work of demolition commences. — Although the largest Octopods, of which we have any account that is entirely free from doubt, did not measure above 4 feet between the ends of the arms ; yet the inhabitants of several parts of the warmer regions of the globe confidently assert, that much larger ones are to be met with. These are said to extend their arms out of the water, and thus to lay hold of men, or of the masts of small vessels. The inhabitants of some of the islands in the Indian Archipelago are said to affirm, that Cuttle-fish are often seen two fathoms (12 feet) broad over their centre, with arms nine fathoms (54 feet long) ; and are stated to provide themselves with axes, whenever they go out in boats, from their fear of being seized by these monsters. Allowing for a great deal of exaggeration in these accounts, it is still probable that Octopods exist in the open sea, of much larger size than any with which we are familiarly acquainted. 962. The ARGONAUTID^E are distinguished from the other Octopod Cephalopoda by their possession of an external shell and by the wide dilatation of two of their arms. A well-known species is the Argonauta, commonly called the " Paper-Nauti- lus," from the whiteness and delicacy of its shell. As the ani- mal has Ifttle in common with the true Nautilus, it would be much better if the latter designation were entirely abandoned, and that of " Argonaut " substituted for it. The shell is not 348 ARGONAUT, OR PAPER-NAUTILUS. chambered, as in the true Nautilus ; but possesses one spiral cavity, into which the animal can withdraw itself entirely. The FIG. 646 — ARGONAUT, OB PAPER-NAUTILUS. animal, however, has no muscular attachment to its shell ; whence it has been supposed by many Naturalists to be a parasitic in- habitant, which had taken up its abode within it ; the shell, from its resemblance to that of the Carinaria (Fig. 682) being ARGONAUT. 349 imagined to have been really formed by an animal allied to that genus. It has been proved, however, by the interesting ex- periments of Madame Power (who has kept a number of these animals in a kind of cage inclosed from the sea in the bay of Messina), that the shell increases regularly with the growth of the animal ; and that the Mollusk possesses the power of repair- ing the shell when injured, in a manner corresponding to its original formation ; whence no reasonable doubt can exist, that the Argonaut is the real constructor of it. 963. Of the eight arms of the Argonaut, six taper gradually towards the extremities ; but two are expanded into wide mem- branous flaps. From very early times, this animal has been reputed to swim on the surface of the sea, using its arms as oars, and spreading these expanded membranes as sails, so as to be wafted along by the wind. But it is now known by accurate observation of the living animal, that this is altogether a fiction (though an interesting one) ; and that the expanded membranes are spread over the sides of the shell, meeting along its keel or edge, and completely inclosing it. It is by these, indeed, and not by the surface of the body itself, that the calcareous secre- tion is poured out, for the enlargement or reparation of the shell. It will be observed that there is a double row of suckers along the edge of each of the expanded arms ; and by these suckers they are held in close contact with each other along the keel of the shell. When the animal withdraws its whole body into the shell, the exterior of the latter is about half uncovered, the ex- panded arms also being partly drawn in. By the action of the arms, and the expulsion of water from its branchial chamber, the Argonaut can swim backwards in the same manner as other Octopods ; and it can also creep along the bottom of the sea. 964. The Decapod section, which, besides the eight ordinary arms, has two longer and slenderer ones, usually denominated tentacles, presents many points of approach to the Tetrabranchi- ate Order. This affinity is indicated, not merely by the in- creased number of the external arms, but by their smaller size in proportion to the body, by the frequent development of a second row of small tentacula within the others, and by several 350 LOLIGIDJi J SEPIIDJE ; SPIRTJLID^. internal characters, especially the development of a chambered shell, of which we find some traces in most of the different forms included in it. Of the three great families into which this group may be divided, the LOLIGID^E, commonly known as Calamaries or Squids, are distinguished by their elongated bodies, with the fins confined to the apex, and by the horny nature of the repre- sentative of the shell, which consists of a slender stem, and two lateral dilatations, giving it somewhat the aspect of a feather, whence the name of pen is usually applied to it. The arms, and especially the two tentacles, are generally of considerable length, sometimes very long. In Chiroteuthis (Fig. 643), the tentacles are sometimes six times as long as the body. The Calamaries are all active, and swim rapidly. To this family belongs the Loligo (Fig. 640), already several times referred to ; small spe- cimens of this genus are frequently left on the beach by the tide on our coasts, but the species are essentially inhabitants of the open sea. In the Onychoteuthis the clubbed extremities of the tentacles are armed with hooks, and the animals are said to em- ploy the small suckers with which the bases of the clubs are furnished, to unite them at this point, so as to form a pair of grasping forceps with which they seize their prey. — The SEPII- DM, or true Cuttle-fish, are stouter in their form than the Cala- maries, and their bodies are bordered throughout on each side with a fin. The internal shell is a calcareous, laminated, cellu- lar plate (the pounce-bone, which may be picked up on every coast), usually presenting an indistinctly chambered apex. The common Sepia, from which the Cuttle-Jish bone of the shops is derived, is a native of British seas. The bone was formerly used in medicine, but is now employed only for the formation of pounces. The most evident approach to the tetrabranchiate forms amongst the living Cephalopoda of the present order, is made by the curious little family of the SPIRULID^E, of which a few spe- cies exist in great abundance in the seas of warm climates, where their singular shells may be picked up on almost every sandy shore. These shells are spiral, with the whorls separate, and the interior divided into several chambers by little trans- verse partitions, which are penetrated by a slender siphon run- BELEMNITES. 351 hing along the smaller curve in the same way as in the Ammo- nites (Fig. 649). This structure, as we shall see, is very much like that prevailing amongst the species of the following order, and which will be explained hereafter ; but the shell, instead of being external, is completely enclosed within the posterior part of the body of the animal. 965. With this order we are also to associate an extremely interesting fami- ly, that of the Belemnites, whose remains abound in several of the older rocks, es- pecially the Lias and Oolite. The shell Consists of a conical-chambered portion, implanted (as it were) into a corre- sponding hollow of a long solid sheath, tapering to a point at its lower extrem- ity (Fig. 647). The conical chambered portion extends considerably beyond the hollow of the stony sheath ; but the border of the latter seems to have been prolonged forwards in a horny condition, so as still to envelope the chambered cone. In the last or largest chamber of the cone, distinct remains of an ink-bag have been frequently met with ; from which it has been argued, that, notwith- standing the strong resemblance of the shell to that of many genera allied to the true Nautilus and belonging to the Te- trabranchiate group, the animal must have been Dibranchiate, and must have included the shell, together with its mas- sive sheath, in the same manner as the Cuttle-fish included the pounce-bone. This argument was founded upon the fact, that the Nautilus — the only Tetrabranchiate Cephalopod now living — possesses no ink-bag ; its power of withdrawing the body completely into its shell, rendering such a means of protection unnecessary : and its justice has been made evident by the dis- FlG. 647 — BELEMNITES; a, large extremity, showing the insertion of; the chambered cone into the sheath. 352 BELEMNITES. — ORDER TETRABRANCHIATA. covery of specimens of Belemnites, in which the soft parts of the animal are so well preserved, as to enable their form and general structure to be distinctly traced. From these it has been ascer- tained, that the arms were furnished with hooks, as in the Ony- choteuthis ; and that the body had a pair of small lateral fins situated at about the middle of its length. From the weight of its dense internal shell, the Belemnite may be supposed to have commonly maintained a vertical position ; and, as its chambered portion was provided with a siphuncle analogous to that which we find in the Nautilus (§ 966), the animal probably had the power of ascending and descending in the water with facility. It would rise swiftly and stealthily to fix its claws in the belly of a fish swimming at the surface above ; and then, perhaps, as swiftly dart down and drag its prey to the bottom, and devour it. We cannot doubt that, like the hooked Calamaries of the present seas, the ancient Belemnites were the most formidable and pre- daceous of their class. ORDER IL— TETRABRANCHIATA. 966. From the remains preserved in a fossil state, the Cepha- lopoda of this Order appear to have been formerly most abund- ant in our seas ; as they present themselves throughout almost all marine strata, from the very earliest of the Palaeozoic series, to those of a comparatively recent epoch. Yet some causes, of which we are at present ignorant, have produced the almost entire extinction of the Order ; the only existing representatives of it being the well-known Nautilus pompilius, or Pearly Nau- tilus, so named from the nacreous lining of its shell, and two or three allied species. The shell of the Nautilus is well known ; being found on most shores between the tropics. Of the animal which constructs it, however, Naturalists had, until recently, the most vague and incorrect ideas, — the Nautilus being very rarely met with in the living state, owing to its being an inhabitant of the open sea, and possessing the power of sinking at the slightest alarm. The general structure of the shell, which may be taken ORDER TETRABRANCHIATA ; — NAUTILUS. 353 as a type of the whole group of chambered shells, will be evident from the accompanying figure ; which represents it laid open. g FIG. 648.— PEARLY NAUTILUS, with the shell laid open : t, tentacula ; e, funnel ; p, hood ; m, portion of mantle ; o, eye ; g, siphon. Externally it presents nothing remarkable, being a flattened spiral; but when its interior is examined, it is found to be divided into chambers, by a large number of transverse partitions of shelly matter. The outer chamber is by far the largest, and to this the body of the animal is restricted ; but it maintains a connection with the rest by means of a membranous tube, called the siphuncle (g, Fig. 648), which passes down through a per- foration near the centre of each partition, and thus penetrates even to the innermost and smallest chamber. Although the history of the growth of the Nautilus cannot (for want of a sufficient number of specimens) be positively stated, there is every reason to believe that, at the usual period for the enlarge- ment of the shell, the animal adds to the edges of the outer chamber, in such a manner as at the same time to prolong and widen it; and that it then throws a new partition across its lower or inner part, so as to form an additional chamber. Hence 354 ORDER TETRABRANCHIATA ; — NAUTILUS. the number of chambers would vary in different specimens, according to their respective ages, and the consequent number of additions they have made to their shells ; and this is found to be the fact. 967. The general structure of the animal is intermediate between that of the Dibranchiate Cephalopods and that of the Gasteropods. The tentacles are numerous, amounting to more than a hundred ; they are slender, tapering, and retractile ; and instead of being furnished with suckers, as in the Octopods and Cuttle-fishes, are more or less distinctly annulated. The inner tentacles are called labial tentacles, as they are attached to a membrane surrounding the mouth ; the sheaths into which the outer tentacles are retractile, are considered to be analagous to the arms of the dibranchiate Cephalopods ; and the dorsal pair of these are united and greatly dilated, so as to form a broad hood, which serves to close the aperture of the shell when the animal is retracted. Of the habits of the Nautili, little is known. They are said to creep along the bottom of the sea, and probably feed upon the Crustacea which they find there, as the specimen dissected by Professor Owen contained portions of a small crab. According to Rumphius, they are sometimes driven up from the bottom by storms, and are then seen, after the weather has again become calm, floating in troops at the surface, with the mouth of the shell upwards. The power of rising and sinking in the water at pleasure which has been attributed to the Nautilus, but its possession of which appears to be very doubtful, has been accounted for by the chambered structure of its shell ; and by a power which it has been supposed to possess, of diminishing its bulk, by forcing water from the. sac which surrounds the heart into the siphuncle, — or allowing it to be expelled from that tube by the elasticity of the air in the chambers, when it desires to increase the bulk of the soft parts of its body. If such increase and decrease in bulk could be effected without any change in the weight of the whole mass, it would be caused (according to well-known principles of Hydrostatics) to ascend or descend in water ; the animal with its shell being altogether of so nearly the same specific gravity with that fluid, that a very slight NAUTILITE; — ORTHOCERATITE ; — AMMONITES. 355 difference in this respect may produce either effect. But this theory, however ingenious, is inconsistent with the fact that, in some of the fossil chambered shells of this group, which we only know from their fossil remains, the siphuncle was evidently con- tinued as a shelly tube throughout, and therefore could not have been distended with fluid ; and even in the recent Nautilus, it does not appear to be possessed of sufficient elasticity to admit the action thus assigned to it. The use of the chambered struc- ture, and of the siphuncle, therefore, still remains unknown. 968. The numbers of fossil chambered shells formed on the same plan, and therefore probably to be regarded as the remains of Cephalopods of similar organisation, is very great. Thus we find in almost all marine strata, from the oldest limestones and sandstones of the Silurian system, down to those covering the chalk, large numbers of shells, very nearly resembling the exist- ing Nautilus, and therefore called Nautilites. Another fossil genus, the Orthoceratite, had a chambered shell, formed upon the same plan with the Nautilus, but straight instead of being spirally curved. In these two genera, — as in some others allied to them, and forming the family NAUTILIDJE, the partitions or septa between the chambers are smooth or simple ; — that is, although they are rather concave on the surface which looks towards the outer chamber, and similarly convex on the other or inner side, they have no inequality or irregularity of surface. Moreover, in both instances, they are usually perforated by the siphuncle nearly in their middle. 969. In the spiral and straight shells which form the family AMMONITID^E, on the contrary, the partitions are very sinuous or wavy, sometimes even forming sharply-bent or zig-zag lines (Fig. 649) ; and the siphuncle usually runs along the outer edge, and may be seen projecting from the surface. These animals are also considered to have possessed an operculum, or shelly valve, for the purpose of closing the orifice of the shell. The Ammonites, commonly called Snake-stones, are among the most abundant of all fossils ; especially in the Lias, Chalk, and Oolite formations. Their size is sometimes very considerable ; Am- monites being occasionally met with of as muAas four feet in 356 AMMONITES. diameter ; and a diameter of three feet being by no means un- common. In some places they are so numerous, that the rocks seem (as it were) composed of them alone. Above five hundred species of these shells have been already de- scribed ; and it appears that many of these were very widely distributed. Thus two species of Ammonites found in the Himalaya mountains, at a height of 16,000 feet above the sea, are exactly like species which are com- T . Tk ± l • mi FIG' 619.— AMMONITE. mon near Lyme in Dorsetshire. These animals must have evidently been very important agents, — their carnivorous habits being duly considered, — in keeping the balance among the other tenants of the seas, by preventing the excessive multiplication of Crustacea, as well as (in all probability) of other Mollusks, and of Fishes. That their mouth was armed in the same manner as that of the existing Cephalopods, is evident from the fact, that Rhyncholites, or fossilized beaks, are found in large numbers, associated with the shells of the Ammo- nites, in the beds in which they occur. It has been suspected by some Naturalists, that the Ammonite might have been, like the existing Spirula (§ 964), an internal, not an external, shell. This idea, however, is inconsistent with the size of the outer chamber, which is quite large enough to receive the animal, usually forming two-thirds of an entire whorl or turn of the shell; and also with the fact that the mouth of the shell, in specimens in which it has been found perfect, is so constructed as to have been evidently connected with the external parts of the animal, and not to have furnished attachment to internal organs. According to Mr. Woodward, also, there is a specimen of an " Ammonite in the British Museum, evidently broken and repaired during the life of the animal, which shows that the shell was deposited from within" The shells of the Ammonites seeming to have been thinner than those of the Nautilites, and their form being less arched, they would have been less capable of resisting pr^ure if they had not been furnished with ribs and AMMONITES. 357 bosses, variously disposed in the different species, for the purpose of strengthening them. In the species represented in the accom- panying figure, these ribs are very prominent. The curiously complicated septa or partitions of the chambers also assisted in strengthening these large shells. FIG. 650.— AMMONIT 970. Several kinds of chambered shells, with sinuous parti- tions, are met with in various strata. These seern to have borne the same relation to the Ammonite, as the Orthoceratite to the Nautilus; and they have been arranged according to their minuter diversities of structure. Some of them are spirally curved, but the several whorls or turns of the spire are not in contact with each other ; this is the case with the Crioceratite. Others are straight, or but slightly curved ; such as the Baculite. The Turrilite, again, has more of a corkscrew curve, resembling that of many Gasteropod shells. — There is good reason to believe that this group, which most abounded* at the period when the Ichthyosaurus and Plesiosaurus were the principal inhabitants of the sea and shores, was preyed on by these marine tyrants ; the remains of the beaks, and even of the horny rings surrounding the suckers, of Cephalopods, having been found in the fossilized excrement of those Reptiles. VOL. II. C C CHAPTER XVI. OF THE CLASS OF GASTEROPODA. 971. GASTEROPODS are those Mollusca, which are provided with a head, and which move from place to place by means of a fleshy disc, or foot, placed under the abdomen. This Class, repre- sented by the snail, is extremely numerous ; and is chiefly com- posed of animals living in a univalve shell, which is usually cone- shaped and rolled into a spiral. Some species, on the contrary, are perfectly naked, or destitute of an external shell : the Slug, for example. The body is elongated, and terminates in front by a head more or less developed, bearing the mouth, which is provided with fleshy tentacula varying in num- ber from two to six ; the back is enveloped in a mantle, which is more or less prolonged backwards, FIG. 651.-CASSIS. an(j which secretes the shell ; and the belly is covered on its under side by the fleshy mass of the foot. The viscera, lodged on the back, occupying the superior part of the buckler or cone formed by the shell, always remain inclosed there ; but the head and foot project beyond it, when the animal unfolds itself for the purpose of walking ; and re-enter the last turn of the spiral, when it again contracts. Hence the size of this last part of the shell, and the form of the opening, are in keeping with the size of the foot. In most aquatic Gasteropods whose shell is spiral, there is a horny or calcareous disc, called the operculum (Fig. 652, o), which is attached to the posterior part of the foot, and which closes the entrance of the shell when the animal withdraws itself. 972. The heart is always systemic (AxiM. PHYSIOL. § 281), and is composed almost invariably of a ventricle and an auricle (Fig. 639) ; it is placed near the back of the animal, opposite that side occupied by the reproductive organs. — The organs of Respiration are formed in some instances for aerial, in others for aquatic, respiration. In the first case they consist of a cavity, on whose walls the blood-vessels form a complicated net-work ; and into the interior of which the external air penetrates, through an orifice in the outer border of the mantle. This pulmonic, or lung-like cavity (Fig. 661), is situated on the back of the CIRCULATION AND RESPIRATION OF GASTEROPODS. 359 animal, and is lodged in the last turn of the spiral shell, when the Mollusk is provided wi th an envelope of this kind. Among Fig. C52 — ANATOMY OF TURBO PICA : p, foot ; o, operculum ; t, proboscis ; ta, tentacula , y, eyes ; m, mantle opened longitudinally, to show the disposition of the respiratory cavity ; /, anterior border of the mantle, which, in its natural position, covers the back of the ani- mal, leaving a wide slit by which the water enters the branchial cavity; b, the gills; c&, branchial vein, returning to the heart, c; ab, branchial artery; a, anus; i, intestine; et stomach and liver; or, oviduct. On the upper side of the neck are seen the cephalic gang- lion, and the salivary glands. And at d is shown a fringed membrane, which forms the lower border of the left side of the opening that leads to the respiratory cavities. those Gasteropods destined to breathe in water, the arrangement of the gills varies considerably ; in many, these organs are lodged in a cavity analogous to that which constitutes the lung of a the preceding (Fig. 652) ; but in others, they are placed be- tween the mantle and the foot, or even on the back of the ani- mal, so as to float freely in the '' surrounding liquid. As ex- amples of the pulmonic Gas- teropods, we may mention the Snail, and the Slug, which live on land ; and the Lymnasn, the FIG. f.53. — PLETJROBRANCHU8 : m, the mantle turned back to show the gills, !»• : a, the anus ; b, mouth and proboscis ; t>, hood ; t, tentacula ; p, foot. 3GO RESPIRATORY AND DIGESTIVE APPARATUS. Planorbis, and others, which live in stagnant waters, and come to the surface to take in the air necessary for their respiration. Among Gasteropods provided with gills inclosed in a dorsal cavity we find the Volutes, Whelks, Cowries, Olives, arid many others. The Limpets and Pleurobranchi (Fig. 653) have these organs in the furrow which separates the foot from the mantle ; a ad in the Doris (Figl 678), the Eolis (Fig. 654), and others, they con- sist of folds or tufts, sometimes very numerous, fixed to the dorsal surface of the body. 973. The mouth of Gasteropods is surrounded with con- tractile lips, and is sometimes armed with horny teeth, which occupy the palate. In several other animals of this class, the anterior part of the palate is very fleshy, and can be made to project outwards, so as to form a proboscis. The lower part of the mouth and oesophagus is occupied by the tongue, or lingual ribbon, as it is sometimes called, which is covered in most cases with an immense number of minute silicious teeth. This ribbon is usually of great length, sometimes longer than the whole body of the animal ; its anterior part is flattened out, and turned over, so as to enable the teeth upon it to be used ; the posterior part, which bears a reserve of teeth, has its margins rolled together so as to form a sort of tube. The form and arrangement of the teeth upon the lingual ribbon in the Gasteropoda have recently ac- quired great importance in the systematic arrangement of these creatures. In some cases, the stomach also is provided with cartilaginous, or even calcareous, projections or teeth, fitted to divide the food. The intestine is bent upon itself, and is lodged between the lobes of the liver and ovary : lastly, the anus is situated nearly always on the right side of the body, at but a little distance from the head. 974. In this Class, the organs of sensation are less developed than in the Cephalopods ; the tentacula, which most Gasteropods GENERAL CHARACTERS OF GASTEROPODA. 3CI carry in front, serve but for touch or smell. Their apparatus for hearing is very simple ; consisting of a little sac on each side which is almost imbedded in the cephalic ganglion. The eyes, which are sometimes wanting, are very small, and of a very simple structure ; sometimes they are situated on the head, and sometimes carried at the base, the side, or the point of the ten- tacula. The Nervous System is less developed than in the pre- ceding Class; and is chiefly composed of a cephalic ganglion, which is connected with others, either placed immediately be- neath the oesophagus, or scattered in distant parts of the body, according to the position of the organs they respectively supply, which varies considerably in this group. (See ANIM. PHYSIOL. § 438.) 975. Of these animals, some are terrestrial, some inhabit fresh waters, but most live in the sea. In general they are formed for crawling, as the Snail, the Whelk, the Limpet, &c. ; but sometimes they are rather adapted for swimming, as is the case with many of the naked Gasteropods. A few of this class attach themselves to the surface of rocks, and pass a great part of their lives with little variation in place. This is the case with the Limpet for example ; which is frequently found par- tially imbedded in a hollow exactly fitting to its shell, and therefore evidently formed by its own action. But the attach- ment of such is not a solid union like that of the Oyster and some other Conclufera ; being only produced by the adhesion of the muscular disc, or foot, which, acting like a sucker, can be detached at any time by the will of the animal. 976. As already remarked, the Shells of Gasteropoda, where they exist, are usually formed in one piece, or are univalve. There is no instance of a Gasteropod forming a bivalve shell, unless we consider the large calcareous " operculum of some of these Mollusks in the light of a second valve, with which it cannot be rightly compared. But there is a group, nearly allied to the Limpets, which is distinguished by the possession of a multivalve shell (Fig. 584); the valves being disposed like the segments of Articulated animals, and being connected by a complex muscular apparatus, which strongly reminds us of that 362 FORM AND STRUCTURE OF SHELL. which binds together and moves the several segments in that sub-kingdom. The material of which the shell is composed, varies considerably in regard to the relative quantities of animal and of calcareous matter which it includes. In the Cones, Cow- ries, Olives, and others known as porcellanous shells, the quantity of animal matter is so small, that it can with difficulty be detected ; but in others, as the Limpet, there is considerably more ; and in some instances there is an almost entire absence of calcareous matter, the shell having merely the consistence of horn. — It is remarkable that, notwithstanding so many of this group are destitute of shell in their perfect condition, all the species belonging to it possess the rudiments of a shell when they come forth from the egg ; and this has nearly the same form in every case, being usually a simple cone, with the point slightly turned over. In most Gasteropods this shell is retained, and is enlarged by successive additions ; but it soon falls off in those cases, in which it is not to be permanent. The additions which are made to the shell, for the purpose of deepening its cavity and widening its mouth, sometimes appear to be confined to the edge only ; whilst in other instances a new layer is thrown out as a lining to the whole interior of the shell. In the former case the line of junction between the old and the new parts is often marked externally by a prominent rib ; but the internal surface is beautifully smoothed off. 977. The forms of the shell in this Class are subject to great variations ; but those which appear most widely separated, may be shown to be connected by intermediate links ; as well as to have a common origin. The simplest of all shells in point of form, is that of the common Limpet, which is merely a cone, more or less expanded at the base ; and in which the successive additions are all made in the same direction. In an allied genus, the Pileopsis, we find the point or apex of the cone somewhat prolonged and turned over, so as to resemble a " fool's cap" in its form ; and the increase of this tendency produces a regular spiral shell, such as that of the Planorlis, in which all the whorls or turns are upon the same plane, — as in a " Catherine's wheel." But if the whorls do not continue in the same plane, but turn FORM AND GROWTH OF SHELL. 363 Fio. 655.— SECTION OP ACHATINA COLUMNARIS. round a central line in a corkscrew-like mode, a shell is formed like that of the common Snail, or the Pleurotoma (Fig. 665). From forms of this kind, we may return to the Dentalium, — which has a long straight cone, like that of the Limpet narrowed and drawn out, — by the Scalaria or Wendletrap, in which the coils of the spire touch each other only by their ribs ; and by the Magilus and Vermetus (Fig. 672), in which the commencement only of the shell possesses a spiral form, the remainder being prolonged into a tube which nearly approaches the straight direction. When the whorls revolve around a ver- tical line, instead of remaining in the same plane, a sort of central pillar is formed, which is termed the columella (Fig. 655) ; this is usually grooved at its lower part, for the passage of water to the respiratory organs. 978. The margin of the shell is not unfrequently fringed with spines, as in the Murex ; these are formed (as are similar ap- Fro. 656.— MURBX 'I KNUISPINA. pendages in the Conchifera,) by prolongations of the Mantle ; and the dissimilar number of them in different specimens has caused the establishment of many species, which, now that the habits of the animal are better known, prove to be but varying forms of the same. For it has been ascertained that the animal has not only the power of forming new spines, but of removing 364 CHANGES OF SHELL WITH AGE. old ones, especially such as would interfere with the continued growth of the shell. The edge of the Mantle is applied against their bases, and a kind of absorption of shelly matter seems to take place, a notch being formed, which causes them to be easily broken off. Various analogous changes are produced by a similar action in other shells, the portions first formed being wholly or partially removed. Sometimes the walls of the older portions are thinned for the purpose of lightening the shell ; and in other cases the top of the cone is altogether removed, a groove having been formed around its interior, which renders it so weak as to be easily broken off ; in these last cases, the animal previously withdraws itself from the part that is thus to be separated, and throws a new partition across, by which the top of the shell remains closed after the division. A shell thus deprived of its apex is said to be decollated. 979. It is not only by such removals, that the form of uni- valve shells undergoes a great change. Sometimes additions are FIG. 657. — FTEROCERAS SCORPIO : a and b, back and front views of the young shell ; c and d, the same of the adult. made to them, which completely alter their figure, so that two individuals of different ages would be scarcely supposed at first CHANGES OP SHELL WITH AGE. 365 sight to belong to the same tribe. But in all these cases, the form of the young shell may be traced in that of the adult. The accompanying figures of the Pteroceras show this change in a moderate degree ; in other genera it is much more remarkable. In another group of shells, of which the common Cowry is an example, a still more curious alteration takes place. In the young shell the edge is sharp, and the mouth an opening of con- siderable breadth. This state continues as long as the shell is increasing in size ; but when it has arrived at adult age, the outer FIG. 658.— CYPKAA EXANTHKMA : a, young shell ; b and c, back and front views of adult shell. lip is thickened, and brought so near the other as to leave but a narrow chink between them. At the same time, a prolongation of the mantle on each side deposits a new layer of shelly matter on the outside of the previous one ; and as the two' prolonga- tions meet along the back, (the line of their junction beino- usually evident on the shell), this additional coat, which is very hard and porcellanous in its texture, incloses the whole previous shell. — The operculum is principally confined to the aquatic Gasteropoda. It is sometimes of the same texture as the shell itself, and sometimes horny. It does not always close the entire 366 SUBDIVISIONS OF GASTEROPODA. mouth of the shell ; but it is sometimes made to fit it, at all stages of growth, with the most beautiful accuracy. Some of the land species also possess an operculum ; but in general they are destitute of it, and they form during hybernation a temporary closure to the mouth of the shell, by a viscid secretion, which hardens into a thin plate, and includes within it a bubble of air. Behind this, a second and even a third similar partition is occa- sionally found, as in the common Snail. 980. The sub-division of this extensive class into Orders is effected by arranging the different tribes according to the cha- racter and position of the respiratory organs. The class may be divided in the first place into the Gasteropoda proper, in which the foot forms a muscular disc, adapted to enable the animal to walk or creep ; and the ffeteropoda, already referred to (§ 947), in which the foot is small and usually compressed, and the ani- mals generally swim. The true Gasteropoda form three Orders. I. PULMONIFERA. — These are for the most part terrestrial species, and all of them are adapted to breathe the air by means of a pulmonary sac, or air cavity, the orifice of which they can open or close at will. They are usually furnished with a large spiral shell ; but in some species the shell is small and internal, and in others entirely wanting. The other two Orders are bran- chiferous. II. PROSOBRANCHIATA. — In which the branchiae are situated in an arched chamber formed by the mantle above the neck, and in front of the heart. All these animals possess a shell, which is usually large enough to conceal its possessor when retracted. III. OPISTHOBRANCHIATA. — In these the branchiae are more or less exposed on the back of the animal, usually towards the hinder part of the body, and consequently behind the heart. Most of the species are destitute of a shell ; a few have an in- ternal shell. IV. HETEROPODA. — The second, or aberrant section of the Gasteropoda, forms only a single Order. The foot is not adapt- ed for creeping, and the animals swim about freely in the open sea. The branchiae, when present, are usually placed on PULMONIFERA ;— SLUGS. 367 the posterior part of the back, and frequently protected by a shell. OKDER L— PULMONIFERA. 981. Although the greater part of 5he Mollusks of this Order live on land, some are aquatic ; but these, like the aquatic FlG. 659.— LIMAX RUFUS. air-breathing Insects and Vertebrata, are obliged to come occa- sionally to the surface to breathe. They all feed upon vegetables, and many of them do so exclusively ; but some are extremely voracious, and will devour almost any organised matter that falls in their way. They are diffused through all climates, particular species being restricted to each. Those with a mi- nute shell, usually concealed within the mantle, commonly known as slugs, constitute the family LIMACID^E. In the com- mon Slugs, as in most of' the terrestrial species of this Order, we observe a prominent head, with four tentacula ; and at the end of the longer pair the eyes are situated. These tentacula can be drawn inwards by a process resembling the inversion of the finger of a glove. On the back there is a kind of shield or disk, formed by the mantle, which usually incloses a small shell. This shield covers the pulmonary sac, the opening of which is on the right side, and the head can be withdrawn beneath it. The Testacella is a kind of slug which has the disc of the man- tle at the posterior extremity, and this always contains a small shell. This animal, which feeds largely on earth-worms, is abundant in the south of France, and has lately been introduced into the gardens of this country, where it is multiplying rapidly. 363 PULMONIFERA ; — SNAILS. — The ONCIDIID.E are nearly allied to the slugs. They are com- pletely covered with a coriaceous mantle, which is broader than FIG. 660 — TESTACET.I.A ap p the foot, but contains no shell. Their usual residence is on aquatic plants, in the marsty districts of warm climates ; but several species are found on the sea-shores, where they dwell within reach of the waves. 982. The Snails, and their allies, constituting the family HELICID^E, are closely allied to the Slugs in organisation ; differ- ing in but little else than the possession of a shell, into which the body may be withdrawn. The Common Garden-Snail of this country, and the Helix pomatia^ or Edible Snail of France and Italy, are well- known examples cv of this family. More striking ones are to be found, however, in tro- pical climates. Among the mem- bers of this group, we may especially notice the genus Anastoma, which FIG. 661.— ANATOMY OF SNAIL; /, foot; f, tentacula half IS distinguished by contracted; d, a sort of diaphragm, separating the respira- .1 -v^.,1;.,,. fnrm tory cavity from the other viscera ; s, portion of the sto- l mach ; I, liver; o, ovary ; i, intestine; r, rectum, or last and position of the part of the intestine; a, «nus ; ft, heart; ap, pulmonary . _ , , .. artery, distributed over the walls of the pulmonary cavity, mouth Ot the Shell p ; ar, aorta; v, secreting gland for the mucus which in the adult covers the body ; cv, its excretory duct, opening near the anus. ing its early life, ita mouth is in the same position as that of other snails ; PULMONIFERA ; — ANASTOMA ; BULIMUS ; ACHATINA. 369 and thus it continues until the shell is increased for the last time. The direction of the curve is then entirely changed ; a mouth with thickened lips and projecting teeth is formed, so as to be on the same plane with the spire ; and from henceforth FIG. GG2.— ANASTOMA it must crawl with the spire downwards, unlike all other snails. Some species of the genus Bulimus, of which the greater part are found in tropical countries, attain to great size, the ejrgs FIG. 6G3.— «, ACHATINA ZEBKA; I, ACIIATISA VIRGINKA (art-versed species;. being as large as those of a pigeon. The species of the allied genus, Achatina, are also of great size, some of them measuring 370 PLANORBIS ; — LIMN.EA ; — AKCYLU8. about eight inches in length ; the eggs of these gigantic Snails are more than an inch long, and enclosed in a brittle, calcareous shell. In certain species of the latter genus, the direction of the coils of the shell is opposite to what it is in other spiral shells ; such are said to be reversed. A European species is one of those most remarkable for the decollation of its shell. 983. The aquatic Pulmonifera have only two tentacula ; and the eyes are placed upon the head, at the base of these, instead of being supported at the extremities of tentacula. They are, of course, under the necessity of coming frequently to the surface to breathe ; and usually live in water of inconsiderable depth, such as ponds and small streams. They feed on the leaves of aquatic plants, especially when in a state of incipient decay. The LiMNvEiD^E, including the well-known Pond- snails, have a thin shell with a simple aperture. :They are exceedingly abundant in ponds in this country, living for the most part amongst the weeds ; but they are also capable of floating at the surface of the wa- ter with the shell down- wards, and when in this position can even glide slowly along by ths action of the foot. The P/anorbis, the shell of which is quite flat having all its coils upon the same level, is a very common genus in this country ; as is also the Limncea, which feeds upon seeds, as well as the softer parts of plants, and the stomach of which has a very muscular gizzard. The curious genus Ancylus has a limpet-like shell ; the species live in streams, and are known as River-limpets. The AURICULID^E closely resemble the Limnaei- da3, but have a stouter shell, with the margins of the aperture toothed. The species are generally found in the brackish water of salt-marshes and tidal streams ; some of them even frequent the sea-shore. A few species, are terrestrial in their habits. The CYCLOSTOMID^E are distinguished from the preceding Pulmoni- FIG. 664.— LIMNJSA STAGXAI.IS. ORDER PROSOBRANCHIATA. 3J1 terous Mollusca by the possession of an operculum. They have an ample spiral shell, and only possess two tentacles, with the eyes on little tubercles at the outside of their bases. In the genus Cyclostoma, of which one species is found on chalky soils in this country, the loot is divided beneath by a longitudinal groove, and each half is used alternately in walking. Most of the species are inhabitants of warm climates, and they resemble the Snails in their habits. ORDER II.— PROSOBRANCHIATA. 984. The Prosobranchiata, which are nearly all marine, con- stitute by far the largest and most important Order of the Gas- teropoda. They are all furnished with an external shell, which is usually of a spiral form, with the last turn of the spire large enough to receive the entire animal within its cavity ; the branchiae, which are of a pectinated or feathered structure, are almost always placed in an arched chamber formed by the man- tle, and situated above the neck, and in front of the heart, the auricle of which is placed in advance of the ventricle. The species in which these characters are exhibited in the greatest perfection form the great section of the Pectinibranchiata, which includes by far the greater portion of the Order. The remainder, which may be regarded as aberrant forms, constitute two smaller sections, of which the Cyclobranchiata have the plume-like branchiae situated at the margin of the body, between the man- tle and the foot ; whilst the Cirrhobranchiata are distinguished by having the head surrounded by numerous cirrhiform organs, which have been regarded as branchiae by many authors, al- though their function appears still to be rather problematical. As the families belonging to this Order are exceedingly numer- ous, we shall only refer in detail to some of the most important of them. 372 SECTION A.— PECTINIBRANCHIATA. 985. The animals of this section, which may be regarded as the most characteristic of Gasteropods, have all two tentacles and two eyes ; the latter being sometimes mounted on footstalks, as in the snail. The mouth is prolonged into a sort of proboscis ; and the foot nearly always bears an operculum. In a considerable number of the species there is a tubular prolongation of the mantle, termed the siphon, for the purpose of con- veying water into the branchial cavity, so that the animal can respire without putting forth its body from its shelter ; and the existence of the siphon is indicated in the shell by a notch or canal at the anterior- margin. The animals in which this con- formation prevails are also furnished with a retractile proboscis, and are for the most part carnivorous in their habits. The ac- companying figure of a Pleurotoma, a shell belonging to this group, is introduced, not only to show this structure, but also for the purpose of explaining the names which are given by Conchologists to differ- ent parts of a shell, and which are made use of in scientific descriptions. At a is seen the canal for the reception of the siphon ; b, a hollow, here nearly closed up, termed the umbilicus ; c, the internal edge, or left lip, which is partly formed by the columella ; d, the ex- ternal or right lip, the edge of which is free ; e, the notch, or slit, which is characteristic of the genus Pleurotoma ; f, the sinus, or posterior canal ; g, part of the last turn of the spire, which is called the venter or belly ; h, h, the turns or whorls of the spire ; t, the sutures, or lines where these are united to each other. FIG. 663.— Pr.Fur.oTOMA 1UBYI.ONKA. CYPKEIDJE, OE COWRIES. 373 986. The group of Mollusca distinguished by the possession of a siphon, includes several families, the members of which are remarkable for the beauty of their shells, or for their interesting habits. Of these the CYPR^EID^I, or Cowries, are distinguished by their convoluted shells, with the aperture narrow and run- ing the whole length of the Shell, the outer margin inflected and usually toothed, and the spire generally concealed in the adult shell. The animal walks upon a broad foot, which bears no operculum ; and the mantle covers nearly the whole of the shell. The shells of the animals of this family are remarkable for the brilliancy of their colours, and for the high polish of which they are susceptible. They are pre-eminently porcellanous ; that is to say, they have much of the half glassy appearance of porcelain when they are polished ; and they break with a fracture similar to that of earthen- ware. This results in part from the very small quantity of animal matter they contain. The form of the shell in is like that of the well-known Olives; its edge being thin and sharp ; but it sub- sequently undergoes a very remarkable change, as already de- scribed (§ 979) ; and it is then only that the full beauty is ac- quired by the shell, as it depends on the deposit of the final layer of shelly matter over the whole exterior. The Cypra&idae are almost restricted to warm climates ; where the species are very abundant. The Cyprcea moneta, or Money Cowry, is the current coin of the natives of Siam, Bengal, and many parts of Africa ; it is collected in the latter by the negro women, and is sent thence to distant countries. In Bengal, 3200 of these shells are reckoned to be equivalent to a rupee, or about two shillings of English money. It is also used amongst several savage na- tions to adorn their dress, and even in this country it has been employed as an ornament for harness. Several other species VOL. II. D D 374 CONES; VOLUTES. coloured are used in the same way in various parts of the world. In the Friendly Islands, permission to wear the Cypr&a aurantia, or Orange Cowry, as an ornament, is only granted to persons of the highest rank. The Cyprcea aurora, which is considered the most rare species of the entire genus, is suspended by the New Zealanders to their dress as an ornament. 987. The CONID^:, or Cones, like the Cowries, have the aperture of the shell very long and narrow ; but the outer mar- gin is not inflected, and the form of the shell is quite different. The whole or the greater part of the spire is flat, and this forms the widest part of the shell, which then tapers away in a regu- larly conical form to the anterior extremity, where we find the notch for the passage of the siphon. The foot bears a very small operculum ; and the lingual teeth are long and arranged in pairs. They are very predatory in their habits, and some of them are said to bite the hands of their captors. The shells of this family are in general very beautifully and their markings a peculiar clearness and definiteness. Some of the species are so highly valued by collectors, as to bring a higher price than almost any other shell ; as much as three hundred guineas having been given for a single specimen. The Cones are found abund- antly on the shores of all tro- pical countries, particularly of Asia ; but they become more rare as they approach the northern hemisphere ; and a few species only are found in the Mediter- ranean. 988. The VOLUTHWE, or Volutes, which are also remarkable for the beauty of their shells, somewhat resemble the Cypraeidce in the structure of the animal, of which the mantle usually covers a part of the shell, and in the absence of the operculum ; but the outer margin of the aperture of the shell is not inflected, Fio. 667.— CONUS GENERALIS. BUCCINID^;— BUCCINUM OR WHELK. 375 and the spire is usually distinct and conical. Like the Mollusks of the preceding families, the Volutes are almost confined to the tropical seas, and from the elegance of their form and colouring they are much sought after by collectors. 989. The BUCCINID^E, or Whelks, have a broad foot, well adapted for creeping, which usually bears an operculum ; the eyes are placed on the tentacles or at their base. The shell generally has the aperture wider than in the preceding families, and its anterior margin is either notched or furnished with a short canal directed upwards. This family includes an immense number of species, which vary greatly in form, and are distributed in all seas. The animals of many species are used as food, — those of the Buccinum undatum of our own shores being known as Whelks. The shells are not remarkable for bril- liant colours ; but they present many interesting varieties of form and marking. They obtain their food by means of a long proboscis, inclosing a tongue that is furnished with sharp teeth at its extremity ; by means of which they bore into other shells, and extract the animal from the interior. This proboscis is not merely adapted, like that of the elephant, to bend itself in all directions ; but it may be entirely retracted into the body, by means of a complex muscular apparatus, which completely draws back the point, and the half of the proboscis nearest to it, into the half attached to the head ;— just as when the finger of a glove is pushed back into the part that incloses the palm. When the proboscis is extended, the tongue is protruded, and by the file-like action of its teeth, even the hardest shells are worn away. These carnivorous Mollusks are not restricted in their destruc- PKJ. 668.— BUCCIXUM UNDATUM. 376 PURPURA. tive operations by any ties of kindred ; for the shell of the Whelk itself is not unfrequently found perforated, just as if by one of its own species. 990. To this family also belongs the Cassis, or Helmut-shell, which is one of the largest of the whole Class. Most of the species are inhabitants of tropical shores ; but a few are found on the coast of the Mediterranean. They live at some distance from the shore, on the sand, into which they occasionally burrow, so as to hide themselves. The shells of the Cassis rufa and other species are beautifully sculp- tured by Italian FIG. 659.— CASSIS TVBERO8A. artists, in imitation of antique cameos; the different layers of colouring matter which they contain, strong- ly resembling in hue those of the onyx and other precious stones formerly used for this purpose. Of these, a great variety of or- naments are made ; and of late years a considerable trade has been carried on in them on the Continent. — Numerous other genera are associated in this group ; but it will be sufficient here to notice the Purpura, a shell of comparatively small size, but which is very abundant in some situations on our own coast and elsewhere. The total number of known species is nearly one hundred and fifty ; the largest among them are inhabitants of tropical seas. It has been supposed that the Roman purple dye was obtained from animals of this genus, and a small quantity of colouring matter may be found in the Purpura lapillus of the British coasts. It appears, however, that it was from species of Murex (§ 991) that the ancients procured their celebrated dye. — All the Mollusks of this group, so far as is at present known, have the habit of depositing their eggs in egg-cases, or nida* BUCCINIDjE.— MURICIILE. 377 menta; which are of various forms in the different species, and are attached in different modes. That of the Buccinum is often to be met with on our shores, in the form of a large irregular ball, composed of a number of little vesicles attached together. The Purpura forms a large number of distinct cylindrical cases, which it attaches to the rocks it inhabits. Each of these small cases gives birth to several young, but it is remarkable that these are exceedingly few in comparison with the number of apparent eggs contained in the capsule when just deposited. Of these there are several hundreds, but it seems doubtful whether they are all to be regarded as true eggs. — The Norwegian Zool- ogists, Koren and Danielssen, who consider them as real yelks, assert that a number of them combine to form one young Mol- lusk ; whilst Dr. Carpenter, who has paid great attention to the subject, asserts that the young are formed in the usual way from a single true yelk, and that the other similar bodies serve these young as food. The evidence at present appears to be in favour of the latter view. 991. In the MURICIDJE, or Rock-shells, the animals of which closely resemble those of the Buccinidse, the shell is furnished with a canal for the reception of the siphon, projecting straight from the anterior extremity. The species are exceedingly numerous, and occur abundantly in all seas. Many of them at- tain a large size, and the animals of some are eaten. One of these is the Fusus antiquus, a well-known Whelk, which is said to be preferable to the common Whelk (Buccinum). The shell of this species is employed as a lamp in the Shetland cottages ; it is suspended horizontally, and filled with oil, when the canal serves for the reception of the wick. In many cases the shells exhibit ridges on their surface (called varices) which correspond with the margins of the aperture of the shell at former stages of its growth. This is well seen in the true Murices, of which one species (Murex erinaceus) is so abundant on our south coasts, that its shell is one of the commonest objects on the beach. The ridges in other species are armed with spines, as in the Murex tenuispina (Fig. 656), in which the canal also is greatly elongated. As already stated, the Tyrian purple was obtained from species of 37S STROMBIDJE. — CERITHIID.E. Murex. In their habits the Muricidoa resemble the Buccinidae, preying upon other Mollusca, through whose shells they bore by the agency of their rasping tongue. 992. The last family of the siphonated Gasteropods is that of the STROMBID^E, or Wing-shells, in which the outer lip of the shell is widely expanded, and deeply notched in the vicinity of the siphonal canal. The animal has a small narrow foot, which is not well adapted for the ordinary creeping motion of the Gastero- pods ; but the Strombidse are nevertheless very active, progress- ing by a series of leaping movements. The foot is furnished with a peculiar process, which bears an elongated operculum, serrated on one side ; the proboscis is very large, annulated, and capable of being protruded to a great distance ; and the eyes are very large and perfect, and supported at the extremity of thick footstalks, from the middle of which the short tentacles take their rise. These curiously organised creatures are most abund- ant in the seas of warm climates, where they feed principally on decomposing animal matter. Many of them are of large size and remarkable forms, the surface and margin of the shell being often adorned with spines or large tubercles, as is the case in the Pteroceras already referred to (Fig. 657). The Strombus gigas of the West Indies, a well-known species, is on^e of the largest Mollusca ; its shell often measures a foot in length ; and the apex and spines being filled up with solid shell, as the animal in- creases in age, an old shell usually weighs several pounds. The shelly matter of the interior, which exhibits beautiful pink tints, is much used in the manufacture of cameos ; and immense numbers of the shells are imported into this country for that purpose. 993. Of the non-siphonated Pectinibranchiate Gasteropods, the majority of which are vegetable feeders, the nearest approach to the preceding families is made by the CERITHIIDJE, in which the anterior margin of the aperture of the shell exhibits more or less distinct traces of a canal, and the margin of the mantle pos- sesses a siphonal fold at the corresponding part. The outer margin of the aperture is usually widely expanded. These cha- racters, which especially indicate a resemblance to the Strombidae, are presented with the greatest distinctness by the well-known TURRITELLID.E ; PALUDINA ; PERIWINKLE. 379 Pelican's foot (Aporrhais), which is found on the British coasts. The Cerithiidae are for the most part of small size ; the shell is elongated and spiral ; and the animal is furnished with a foot of moderate size, which bears a spiral operculum, and with a pair of long tentacles, attached to the sides of which are the short footstalks which bear the eyes. They are found in all parts of the world, generally in the sea, although a few species inhabit fresh water. Of the latter, some even quit the water very fre- quently, and these are capable of suspending themselves from plants by means of glutinous threads. 994. In the great family of the TURRITELLID^:, the aperture exhibits no trace of a notch, but the form varies greatly from that of an elongated spiral cone to that of a complete disc. The animal has a broad muzzle ; long, slender ten- tacles, at or near the base of which the eyes are generally situated ; and a horny operculum, which is generally spiral, but sometimes concentric. The water is frequently admitted to the branchial chamber by a fold of the border of the mantle, representing a rrG. 670._AMPUIjLARI. RUG08A rudimentary siphon ; and in the genus Ampullaria, this is much elongated, forming a true siphon. Most of the species are marine, but a considerable number are inhabitants of the fresh waters, especially of warm climates. Of these the Ampullaria (Fig. 670) above mentioned is an example, and another, the Paludina vivipara (Fig. 671), is common in this country. This animal, in common with the other species of its genus, is remarkable for producing its young alive, the eggs being hatched within FIG. 671.-SHELL tne oviduct. Of the marine species, the best- or PALUDINA. t • . known is the common Periwinkle, ot which such quantities are used as an article of food in the countries in which it abounds. It is considered in Sweden to afford a sign of the coming weather ; the peasants having observed that, whenever 380 SCALARIA.—VERMETUS. the Periwinkles ascend the rocks, it is a sure sign of a storm being at hand, their instinct having taught them to place them- selves out of the reach of the dashing of the waves ; when, on the contrary, they make a descent upon the sand, it is an indica- tion of a calm. The true Turritellce have an elongated spiral shell, with a small aperture ; and nearly allied to them is the Scalaria, in which the surface of the convex whorls is adorned with numerous, very prominent, transverse ribs. In some cases the whorls are separate, and only come in contact by their ribs. The principal species of this group — the Scalaria pretiosa, or Wentle-trap — was long famous on account of the high price given for it by shell-collectors. 995. Besides these normally constructed shells, some of the Mollusks of this family form an irregularly tubular habitation, which so much resembles that formed by certain Annelida, as to be scarcely distinguishable from it. They are very few in number. The Vermetus (Fig. 672) is the principal genus of the group. This is remarkable for the close resemblance of its shell FIG. f.T2.— VEUMKTUS. to that of the Serpula (Fig. 629) ; but, when perfect, it may be generally distinguished by the regularly-spiral twisting of its first-formed portion. Some species associate together in large masses, so as even to form reefs ; whilst others attach themselves to Coral, and lengthen their shells in proportion as the Coral grows up around them. When the animal has quitted the lower part of its tube, that it may keep itself at the surface, it usually throws a partition across, in the manner of the Nautilus ; and a tolerably regular series of such partitions is not unfrequently found. In the Magilus, an allied genus of similar habits, whose tube is sometimes lengthened in this manner to as much as three feet, the first-formed part of the shell, instead of being cut off, NEKITID.E. — TURB1NID.E; TROCIIU8. 381 is sometimes completely filled up by the exudation of solid mat- ter. Some modern Conchologists place the Magilus amongst the Buccinidae. 996. We come now to the NERITID^E, which are furnished with a thick and somewhat globose shell, with a small spire, and an entire aperture, which, however, is narrowed by the broad plates which are directed inwards from the margins, and the edges of which are frequently notched. The inner walls of the spire are removed as the animal grows from them, so that the interior of the shell forms a simple cavity. The animal has long slender tentacles, near which the eyes are situated on short foot-stalks ; the lingual teeth are very numerous. The opercu- lum is shelly, partially spiral, and furnished with an appendage on one side near the nucleus. Most of the Neritidse are marine, and they are almost confined to tropical climates. — The genus Neritina is fluviatile in its habits ; one species inhabits Britain. 997. The TURBINID^E, or Top-shells, are nearly allied to the Neritidse, but differ from them in several important particulars. The shell is spiral, and usually more or less conical in form ; and the operculum, which is always spiral in its structure, is destitute of the peculiar appendages of that of the Neritidse. The inte- rior of the shell is pearly. The head is generally furnished with pectinated lobes ; and the sides present several long filaments or cirri. — Of the typical genus Turbo, some of the larger tropical species are often seen with the shelly matter partially or entirely removed, so as to expose the inner pearly stratum. This oper- ation is also performed upon the larger shells of the genus Tro- chus, some of the smaller species of which are exceedingly abundant on our coasts. In the Trochus the form of the shell is pyramidal, the sides being usually nearly straight, and the aperture situated at one side of the flattened base. The shells of the small British species are the favourite habitation of young Hermit Crabs. — Amongst the exotic species we may especially notice the Trochus agglutinans, a native of the West Indies which derives its name from its singular habit of glueing to its shell small pieces of stone, coral, shell, &c. This seems to answer the purpose of strengthening its shell, which is thin and brittle.— 332 NATICIDJE ; — lANTHINID^ ; — HALIOTIDvE. The Trochus longispina, from India, has the circumference orna- mented with a row of long spines of a silvery or gold colour placed at regular distances. 998. The little family NATICID E, in which the shell is al- most globular, is remarkable for having the front of the foot dilated into a broad fold which conceals the head, and the lobes of the mantle very large and covering a portion of the shell. The animal is provided with a long retractile proboscis, and is carnivorous in its habits. The species are all marine, and are found in most parts of the world. 999. The family IANTHINIDJE includes a few species of Mol- lusca inhabiting a beautiful Snail-like shell, and from this cir- cumstance, and the fine violet tint of the base of their shell, they have received the name of Violet Snails. They are oceanic in their habits, floating about freely in the open sea, where they occur in vast numbers together, and are said to feed upon the Velellce, which inhabit the same situations. When irritated or alarmed, the lanthina pours out a violet secretion, which darkens the water around it ; and thus serves for its concealment, in the manner of the ink of the Cuttle-fish. But the most re- markable circumstance in the history of this delicate and beau- tiful creature, consists in its production of a peculiar float or raft, composed of numerous cartilaginous vesicles filled with air, which springs from the small foot in place of an operculum. To the lower surface of this curious float the egg-capsules are attached, and thus the lanthina carries its offspring about with it until the young animals are fully formed. — Nearly allied to these are the HALIOTIDJE, of which the well-known Ear-shells are the types. In this family the shell exhibits more or less of a spiral structure, and there is a notch or perforation for the passage of the anal siphon, which carries away the water from the bran- chial cavity. The aperture is very wide, and there is no opercu- lum. In the Haliotis, or Ear-shell, the shell is very flat and slightly twisted at the apex, and within the convex margin there is a series of perforations, of which those nearest the apex are successively closed by shelly matter. This animal, in its living state, is one of the most beautiful of Gasteropods, on account of HALIOTIS ; FISSURELLID.K J CALYPTR^ID^. — CYCLOBRANCHIATA. 383 the variety and richness of its colours. Its shell, when the sur- face is polished, possesses a pearly lustre, with resplendent me- tallic hues. It is consequently much sought for as an ornament. The animal attaches itself to the rock, after the manner of a Limpet, by a large muscular foot ; and the extent of the adher- ing surface is so great, that a very considerable force is required to detach it, when the animal is putting forth its strength. The best mode of obtaining the shell, is to plftce the hand or some instrument under its edge (which is usually a little separated from the rock when the animal is undisturbed), and to endea- vour to remove it before the animal is alarmed. When this at- tempt is not successful, the animal draws its shell down upon the rock with such firmness, as to grasp most securely anything that is under its edge ; and in this manner fatal accidents have oc- curred to men, who have incautiously attempted to remove these shells, when under water. The Haliotis is very abundant on the shores of the Channel Islands, where it is cooked and eaten. The other species referred to this family have the shell of a more distinctly spiral form. — The nearly allied FISSURELLIDJE have a conical shell, like that of the common Limpet, but furnished with a small aperture at the apex for the escape of the branchial cur- rent ; hence they have received the name of Key-hole Limpets. — In the CALYPTR^ID^E, or Bonnet-limpets, also, the shell has nearly the same form, but the apex is somewhat spiral, and the interior is usually provided with a shelly plate, which is some- times arranged spirally. They adhere firmly to rocks and shells, where they appear to pass a perfectly sedentary existence ; the shells being usually fitted to any irregularities of the surface, whilst in some cases the rock is more or less hollowed out by the foot of the animal. SECTION B.— CYCLOBRANCHIATA. 1000. The general form of the Limpets, which principally compose this Section, is well known ; and the peculiarity in the position of their gills has already been mentioned. Closely allied to the Limpets in general structure, but differing remarkably in 384 LIMPETS ; — CHITONS. — CIBRHOBRANCHIATA. the formation of the shell, are the Chitons ; of which some small species inhabit our shores, but which attain to much greater size between the tropics. Their shell (Fig. 663) is composed of a number of plates arranged behind one another with great regu- larity, and connected by a very complex series of ligaments and muscles, which reminds the Naturalist of those which unite and move the different segments in the Articulated animals. The Limpets and Chitons* fix themselves to the rock, in the same manner as the Haliotis ; and it is stated that Crows and other birds, which endeavour to detach them for food, are sometimes caught by the points of their bills, and held firmly until they are drowned by the advancing tide. The Limpets are herbi- vorous, feeding upon sea-weeds, which they reduce with their long riband-shaped, rasp-like tongues. Although we usually see them attached quite motionless to rocks, this is because exposure to the air is unfavourable to their movement, since too free an admission of it between their gills would dry them up. It is when covered with water that their activity manifests itself. In many points of struc- ture, the animals of this Order approach those of Bivalve shells. The rock, in the no. 673 -CHITON. Limpet, may almost be regarded as a second valve ; since the muscle takes a firm attachment to its surface, and draws down the shell upon it, in the same manner that the adductor muscle of the Bivalves enables the animal to inclose itself by drawing the two valves of the shell together ( § 1016). Moreover the eyes are very imperfect or entirely absent ; and many other points of internal structure prove the inferiority of these animals to the Gasteropods in general. SECTION C.— CIRRHOBRANCHIATA. 1001. This group 'ncludes only the family DENTALIID^E, the animals of which inhabit a slightly curved, tapering shell, re- DENTAL1UM. — OPI»TIIOBRANCHIATA. 385 sembling the tusk of an elephant, whence the name of Tooth- shells is ordinarily applied to them. The animal is of a cylin- drical form, inclosed in a sac-like mantle, from an aperture at the anterior extremity of which the foot can be protruded. Above the base of the foot, near the middle of the body, the head is situated ; and on each side of this is a tuft of numerous cirrus- like organs, which have been commonly regarded as branchiae, al- though from recent researches it would appear that they are rather to be considered as tentacular organs. The shell has an aperture at each extremity ; its surface is sometimes smooth, and sometimes longitudinally striated. The Dentaliidae occur in most seas, inhabiting a sandy or muddy bottom, in which they usually bury themselves by means of the foot. They are carni- vorous, feeding upon minute marine animals. ORDER III.— OPISTHOBRANCHIATA. 1002. In the second Order of branchiferous Gasteropods, the gills are not inclosed in a regular chamber, but either exposed on the back of the animal, or more or less concealed by folds of the mantle. They are usually of a tufted or arborescent form, and placed on the back or sides of the body, behind the heart. The Mollusca of this Order, which might be designated Sea-slugs, are usually destitute of a shell ; and in those genera which pos- sess a shell, this is almost always internal, and generally rudi- mentary. These animals are all marine, and for the most part carnivorous in their habits. The Order may be divided into two principal sections, in accordance with differences in the position of the gills. In the NUDIBRANCHIATA, these organs are freely exposed on the back or sides of the body ; and the animals possess no shell either internal or external. In the TECTIBRANCHIATA, on the contrary, the animal is frequently provided with a shell, and the branchiae are concealed either by the mantle or by the shell, when the latter is present. 386 SECTION A.— TECTIBRANCHIATA. 1003. The animals of this Section still show an approach to that arrangement of the gills, which characterises the great bulk of the Class ; these organs being concealed beneath a fold of the mantle, in which a small shell is usually contained. They are all marine ; and live chiefly on the shore, or on floating sea- weeds. A very characteristic example of the group is the FIG. 674.— APLY81A. Aplysia, commonly termed Sea-Hare, which is abundant on many parts of our own coasts, and which forms the type of the family APLYSIAD E. Its common name is probably derived from the peculiar form of the superior pair of tentacula, which are flattened and hollowed like the ears of a quadruped. The head has a very distinct neck. The gills consist of leaflets arranged in a complex form, and situated on the back beneath a fold of the mantle, which also frequently incloses a flat horny shell. The digestive apparatus is very complicated ; consisting of a mem- FIG. 675.— BCLI^KA APERTA. FIG. 676.— BULLA LIGNARIA (a): BVLLA AMPULLA (I). branous crop like that of Birds, a gizzard having cartilaginous walls, and a third stomach beset with sharp hooks in its interior. TECTIBRANCHIATA ; APLYSIAD.E ; BU 387 These animals feed on sea-weed. They are very sluggish in their movements, but have a peculiar means of defence, — con- sisting of a deep purple liquid (said by some to have acrid pro- perties), which they can discharge from the edge of the mantle when alarmed, and by which the surrounding water is dis- coloured, so that the animal cannot be discerned. Amongst the singular animals referred to this family, one of the most remark- able is the Bursatella (Fig. 677), an inhabitant of the Indian Seas. Its gills project far beyond the opening of the mantle. — Nearly allied to the Aplysia are the Bulla and Bullcea, which belong to the family BULLID^E. These have a small calcareous shell, in which the spiral form be- gins to manifest itself. The Bullcea apcrta (Fig. 675) is found in almost every sea, living on oozy bottoms. The Bulla lig~ naria (Fig. 676, a) is re- markable for the density of the walls of the sto- mach ; amidst the tendin- ous fibres of which, a large quantity of calcareous matter is deposited, form- ing plates of bony firm- ness ; these are moved against each other by powerful muscles, so as to rub down almost any sub- stance that is placed between them. The Author has more than once found a small bivalve shell in this situation. The shell of the Bulla ampulla (Fig. 676, b) is interesting, as exhibiting, in its flat open form, a transition towards that of the Aplysia. — In juxtaposition with the Bullidaa, some writers place the TORNA- TELLID^E, which are distinguished from all the other species of the Order by their regularly spiral external shell. 1004. The PLEUROBRANCHID.E (Fig. 653) are also gener- FIG. 677.— BUR.SATKI.I.A LfUCHIl. 388 PLEUROBRANCHHm— NUDIBRANCHIATA DORID^. ally furnished with a shell, which is limpet-like, and covers the back of the animal, but is generally more or less concealed by the mantle. The gills are confined to one side of the body, and placed between the margin of the mantle and the foot. These animals feed on vegetable matters, and have an exceedingly com- plicated stomach. The shell of one species is known as the Chinese umbrella. The nearly allied PHYLLIDIID^E have no shell, and the branchiae are placed on both sides of the body. SECTION B.— NUDIBRANCHIATA. 1005. The animals of this Section are found on all rocky coasts, where they usually inhabit rather deep water, creeping about upon sea-weeds, and occasionally swimming. The species are numerous, and some of them attain considerable size ; the Tethys fimbriata (Fig. 680), a native of the Mediterranean, at- taining a length of one foot. The number of those existing on our own shores is much greater than has been usually supposed ; a large number of species having been discovered by recent in- vestigations. These, many of which are exceedingly elegant, are described and beautifully figured in the admirable monograph of the British Nudibranchiata, by Messrs. Alder and Hancock, lately published by the Ray Society. The section has been divided into several families, characterised principally by peculi- arities in the branchial organs. 1006. The DORID^, or Sea-Lemons, are distinguished by having the branchiae placed in a circular form at the hinder part of the body, around the anal aperture (Fig. 678). The upper surface is formed by a broad mantle, strengthened by the deposition of calcareous particles ; the foot is com- paratively narrow ; and near the anterior margin of the mantle is a FTG. GTS. DOR* ARGO. pair of tentacles, usually laminated and retractile, and often accompanied by filamentous prolonga- tions of the mantle. These animals are found on most shores NUDIBRANCHIATA ;— TRITONIAD^l ;— 389 near low-water mark, where they feed principally on Zoophytes. Some of them are more than three inches in length. — The TRITO- NIADJE, which are nearly allied to the preceding, have the branchiae arranged along the sides of the back; the tentacles are retractile within distinct sheaths, and ofte/i accompanied by branched fila- FIQ. 679.— TRITONIA HOMBEB.GII. FIG. 680.— TETHYS FIMBBIATA, TOPER AND UNDER SIDE. ments (Fig. 679).— To this family also belongs the Tethys (Fig. 680) already referred to, in which the head is concealed by a large membranous fringed hood. This animal, which is the largest of the Nudibran- chiata, is said to feed upon other Mollusks and Crustacea. — The MQIADM also have the gills placed on the sides of the back, but the tentacles are not retrac- tile. They are active animals, and swim freely on their backs. In the jEolis (Fig. 654), the gills consist of an immense number of finger-like processes, forming tufts on each side of the body ; some of these receive ca3cal pro- VOL. ii. E E 390 NUDIBRANCHIATA. — HETEROPODA. longations of the stomach and liver. In the Glaucus (Fig. 681), they form two or three large tufts on each side, which give as- sistance in swimming. These beautiful little MoUusks are in- habitants of the Mediterranean and Indian Oceans ; their hues are azure blue and silver. — The small family of the ELYSIAD^E consists of a few minute slug-like animals, in which no trace of special respiratory organs have been detected. They appear to feed upon Sea-weeds. % 1007. Most of the Nudibranchiata deposit their eggs on the shore in gelatinous masses ; the eggs being very regularly ar- ranged in rows or bands. Of the immense number of eggs which some of these contain, an idea may be derived from the following fact, which is mentioned by Mr. Darwin, in regard to the mass deposited by a large white species, about 3J inches long, on the shores of the Falkland Islands. From two to five eggs (each of them 3-1000ths of an inch in diameter) were contained in a little spherical case. These cases were arranged two deep in rows ; and these rows adhered to each other in such a manner as to form a ribbon, — running across it from one edge to the other. One of these ribbons measured twenty inches in length, and half an inch in breadth ; and by counting the number of the spherical cases contained in one-tenth of an inch of each row, and the number of rows in an equal length of the ribbon, Mr. D. ascer- tained that there must have been, in the whole mass, at least six hundred thousand eggs. ORDER IV.— HETEROPODA. 1008. The Mollusks of this Order, which have been regarded by some Zoologists as forming a class distinct from the Gastero- poda, are distinguished from all others by their complete adaptation to an oceanic mode of existence. Instead of creeping about upon rocks and sea-weeds at' moderate depths near the shore, they swim about freely in the open sea, often displaying great activity in their movements. To fit them for this peculiar mode of life, the whole body is much compressed ; the foot usually forms a vertical muscular paddle, serving as a fin, whilst the hindermost ORDER HETEROPODA; — FIROLID^. 391 part of the body, which is also regarded as analagous to one of the divisions of the foot (seen very distinctly in the lobe which bears the operculum in the Strombidae) is enlarged to form a powerful caudal fin, by the agency of which the creatures swim rapidly through the water. At the edge of the true foot, in many species, there is a sort of sucker, by which the animals can attach themselves to floating sea- weeds and other objects. They swim with the back downwards. The branchiae are often want- ing ; and it is curious that this is sometimes the case in particu- lar species of a genus, or even in certain individuals of a species in which branchiaB usually occur. When present, they are generally collected together, with the viscera, into a mass on the back of the animal, which is often protected by a shell ; and in a few species, which are furnished with an ample shell, the branchiae are placed in a regular dorsal cavity. The body is gelatinous in FIG. 682.— CARINARIA . a, mouth ; b, tentacula ; c, eyes ; d, stomach ; «, gills ; /, anus ; g, shell ; h, liver; t. foot; *, sucker. its consistence, and so transparent as to permit much of its in- ternal organisation to be seen. The mouth is furnished with a long muscular proboscis, which can be protruded or drawn in at will ; it contains a rasp-like tongue, armed with recurved spines. They appear to feed on small marine animals. — These singular Mollusks are divided into two families. In the FIRO- LIDJE, which present the characters of the Order in their typical 392 FIROLIDJE; ATLANTID.E.— FOSSIL SHELL3. form, the body is much elongated, the foot presents the pecu- liar structure above described, and the gills are either naked or covered by a small conical shell. The latter is seen in the Carinaria (Fig. 682) ; the shell of which presents a con- siderable resemblance to that of the Argonaut (§ 962) ; in fact, by some naturalists it has been supposed that the shell inhabited by the Cephalopod just mentioned is constructed by a Mollusk allied to Carinaria, and that the Argonaut only makes use of the empty shell as a protection for its body. In Firola there is no sheh1. The animals of this family are inhabitants of the warmer temperate and tropical seas ; several species are found in the Mediterranean. 1009. The ATLANTIC^ are provided with a large shell, with- in which they can retract themselves at pleasure ; and the foot sometimes bears an operculum, with which the aperture of the shell may be closed. The shell greatly resembles that of the Nautilus in form ; and when first discovered, the Atlanta was sup- posed to be the living representation of the extinct Ammonites. The Atlantidae also differ from the preceding family, in having the branchiae inclosed in a regular dorsal chamber. They are found, like the Firolidse, in the seas of warm climates. 1010. To enter into any detailed account of the Fossil Re- mains of this class, would be unsuitable to our present purpose ; and it will be sufficient here to state some general facts in regard to them. Remains of Univalve shells, of such a form and struc- ture as evidently to have belonged to Gasteropod Mollusks, are found in nearly every bed formed by the action of water, from the very earfcest of those containing fossils of any kind, down to the present time. In many instances, the fossil shells, even of the most ancient beds, may be referred to genera which still exist ; — thus a species -of Buccinum is found in the rocks of the Silurian system ; although they do not correspond with any species now living, except in cases where there is reason to believe that the deposit was formed at a comparatively recent period. The Conchologist is generally able to determine, by an examina- tion of the shell, whether it was formed by a marine or & fresh- water Mollusk ; and in this manner he often receives important GEOLOGICAL DISTRIBUTION OF GASTEROPODA. 393 guidance, in determining the circumstances under which a par- ticular deposit was formed. But he cannot be sure in regard to this, from the examination of one or two shells only ; since there are many genera, which contain species of both kinds. He is guided, therefore, by the comparison of all the shells contain- ed in the deposit, with their nearest allies amongst those now existing. Sometimes there is such a mixture of marine and fresh-water shells, as to induce the belief, that the deposit was formed in the estuary at the mouth of a river, of which both might be inhabitants at once. In other cases, the shells are so exclusively fresh-water, as to indicate that the deposit was formed at the bottom of a river or lake ; and in this case, as might have been expected, it is usually of no great extent. When the nature of the shells indicates a deposit from the bottom of the sea, the same shells are frequently found in strata, which differ greatly in their mineral materials, and which present themselves at very different parts of the earth's surface ; and they thus afford important assistance to the Geologist, in deter- mining the real correspondence between these deposits. It is a curious fact, that in all the earlier rocks, down to the chalk- formation, the remains of the carnivorous Gasteropods bear a very small proportion to those of the herbivorous group ; and their place would seem to have been then supplied by the numerous Cephalopods of predaceous habits which then infested the seas (§ 968). Nearly all of these disappeared after the Chalk was formed ; and the proportion of the carnivorous Gasteropods ex- hibits a remarkable increase from that period. 394 CHAPTER XVII. OF THE CLASS OF PTEROPODA. 101 1. NOTWITHSTANDING the small size of the Class PTEROPO- DA, it is interesting in many respects. It may be regarded as representing, in the sub-kingdom Mollusca, the Birds of the Ver- tebrated sub-kingdoms, and the Insects of the Articulated series; and the inconsiderable number of distinct forms which it pre- sents, may probably be accounted for by reverting to the wide departure from the usual Molluscous type, which the animals of this class exhibit in their structure and habits. They are par- ticularly distinguished by the possession of a pair of fin-like FIG. 683 — CLIO BOREALIS. organs, or wings, consisting of an expansion of the mantle on each side of the neck, and furnished with muscular fibres ; by the aid of which instruments, they can be rapidly propelled through the water. The body is uniformly symmetrical ; that is, its two sides precisely correspond, — a condition evidently favourable for rapid movement. It is from the wing-like cha- racter of the lateral appendages, that the name of the class, which means wing-footed, is derived. Although the number of species belonging to this Class is small, and their dimensions are PTEHOPODA.— CLIO. 395- inconsiderable, yet the number of individuals which associate together in shoals is often enormous, so that the sea appears literally alive with them. Some of them are possessed of a shell ; whilst others are unprovided with such a protection. Where it exists, it is very light and deli- cate ; and it seldom covers more than the posterior half of the body (Fig. 684). In one beautiful little Mollusk, the Cym- bulia, it has the form of a slipper ; from the large opening of which, the wings or fins are put forth The head of these animals is usually prominent, possess- no. 684.— HYALvEA. . * ,' ing eyes and sensory tentacula ; and their internal organisation is of a very complex nature. 1012. The Clio (Fig. 683) is one of the best-known genera of this class ; and its general aspect conveys a good idea of that of the whole group. One species of this genus, the Clio borealis, abounds in the Arctic seas ; presenting itself in such vast num- bers, that, when the weather is calm, the surface appears covered with them for miles together ; and an analogous species, the Clio australis, appears to be equally abundant in the Polar regions of the southern hemisphere. These animals are well known to the whale-fishers and others, as whales' food, being among the chief articles on which that monster — the largest existing animal — is supported. It has been asserted that the sea is sometimes so glutted with the Clios, that the whale can- not open its mouth without ingulfing thousands of them. — The chief point of special interest in the structure of the Clio, is the conformation of its organs for the capture and mastication of its food. The six labial tentacula, which are seen to project from the head, and which appear at first sight to be merely fleshy append- ages, are in reality instruments of prehension, most elaborately constructed. Each of these six appendages, when examined attentively, is seen to be of a reddish tint ; and this colour, under the microscope, is found to be dependent upon the presence of numerous minute isolated red points, distributed over its surface. " 396 CLI° BOREALIS. — HETEROPODA. When still further magnified, these distinct points are evidently peculiar organs, arranged with great regularity, so as to give a speckled appearance to the whole of the conical appendage; and their number, at a rough guess, may be estimated to be about 3000 on each. When very minutely examined, every one of these specks is seen to consist of a transparent cylinder, not unlike the cell of a polype, and containing within its cavity about twenty sucking- discs, mounted upon stalks, by which they can be made to project beyond the edge of their sheath, so as to apply themselves to their prey. Thus, therefore, the head cf one Clio will bear about (3000x20x6) 360,000 of these micro- scopic suckers ; an apparatus for prehension, which is, perhaps, unparalleled in the whole animal kingdom. In this manner, these active little animals are enabled to seize and hold their minute prey ; and their mouths are furnished with efficient instruments for reducing it. The jaws, which are placed laterally, as in the Articulata, are furnished with long sharp comb-like projections or teeth ; and the tongue is beset with a vast number of sharp spiny booklets, curved backwards. Besides the prehen- sile appendages just mentioned, two sensory tentacula are capable of being put forth, for the purpose of feeling for the food. The Clio possesses eyes, which, though extremely minute, have a very complete organisation ; and altogether its structure com- pletely corresponds with what has been already remarked hi regard to the character of the Class, as the Molluscous represen- tative of Birds and Insects. 1013. The Clio may be taken as the type of the shell-less Sec- tion of the Class, the members of which, from the nakedness of of their bodies, have been denominated GYMNOSOMATA. Of the THECOSOMATA, or shelled Section, the Hyalcea (Fig. 684) is a good example. The shells of all these beautiful little creatures are of a most delicate glassy texture ; their shape being usually pyramidal, although in many cases prominent angles project from different parts of their surface. In other species, however, the shell acquires a more or less spiral structure ; as in the Limaci- na, the shell of which resembles that of the Nautilus in its form ; and the Spirialis, in which the shell forms a delicate pointed spire, and the aperture is closed by a little operculurn. CHAPTER XVIII. OF THE LAMELLIBRANCHIATE CONCHIFERA. 1014. THIS group is nearly synonymous with that of Bi- valves in the Linnsean arrangement, since nearly all the animals referred to that Section of the Testaceous Worms by the older Naturalists belong to it ; but it also includes a few species whose shells are Multivalve, and some others, in which there appears at first sight an entire departure from the usual form. The Mol- lusks belonging to this class, in common with those of the three following groups, are destitute of a head ; that is to say, the mouth is not situated upon a prominent part of the body, nor assisted in the choice of food by organs of special sensation in its neighbourhood ; but the entrance to the stomach is buried be- tween the folds of the mantle. 1015. The part of the structure of these animals which is best known, is the shell. This is composed of particles of carbonate of lime, exuded from the surface of the mantle, and contained in the cavities of cells, or between layers of membrane (§ 942). If one of the valves of an Oyster be examined, it will be seen to consist of a number of layers, of which the external one is the smallest, each inner one projecting beyond the one which covers it. This is the case with other Bivalves ; but it is more evident in such shells as that of the Oyster, in which the layers adhere loosely together, than in others in which they are more compact, The shelly matter is thrown out at intervals, from the surface of the mantle ; and as the animal enlarges at each interval, the new layer extends beyond the old one. In this manner a constant relation is preserved between the size of the animal and that of its shell ; and the addition of the newly-formed portions, not to the edge only, but to the interior of the whole previous shell, strengthens the latter in proportion to its increase in size. 1016. The valves are connected together in various ways. 398 BIVALVE SHELLS. In the first place, they are jointed by a hinge, which is in some instances so firm and complicated, that it holds them together when all the soft parts have been removed. This hinge is some- times formed by the locking of a continuous ridge on one valve into a groove in the other, and some- times by a num- ber of little pro- jections or teeth, which fit into cor- responding hol- lows in the op- posite valve. In the neighbour- hood of the hinge (sometimes out- side, sometimes inside, or both), is fixed the liga- ment ; which is composed of an elastic animal substance ; this answers the pur- pose of binding the valves to- gether, and at the same time of keeping them a little apart, which may be regarded as their natural position. When the animal wishes to draw the valves closely together, it does so by means of the adductor muscle, which is fixed to the interior of both valves at FIG. 685.— A, a, b, length of the shell ; c, d, height ; e, lunula, above which is the summit ; d, the ventral or inferior edge. B, the line across marks the thickness of bivalves. c, a, anterior extremity ; 6, posterior ; c, d, muscular impres- Bions ; e,f, pallial impression ; g, lower edge of the left valve. GENERAL STRUCTURE OF LAMELLIBRANCHIATA. 399 some distance from the hinge, and of which the insertion can be easily traced by a somewhat rough depression or pit, on the in- terior surface of each valve. In some Conchifera, this muscle is single, and in others it is double, the two parts being even at oppo- site ends of the valve (Fig. 685, c). Upon this character it has been proposed to found the primary division of the Class into Or- ders ; but the classification thus formed is not a natural one, inas- much as it brings together kinds which have little resemblance, and widely separates others which are closely allied. — In Fig. 685 are shown the several parts of a Bivalve Shell, with the explanation of the names by which they are Described. 1017. In order to describe the general structure of the Lamelli- branchiata, it will be advantageous to select some particular illustration ; and the Mactra (Fig. 686) is well adapted to this purpose. On opening such a shell, it is seen that the two valves are lined by a membrane, in which the animal is enclosed, like a book between the boards of its cover. This membrane is divided into two halves along a considerable part of the edge of the valves ; but is united near the large end. In some Conchifera, as will be presently noticed, the two valves of the mantle are separated along their whole extent ; whilst in others they are completely closed, with the exception of the two orifices for the ingress and egress of water; which are sometimes drawn out into long tubes. In the Mactra, the water enters through one of the short respiratory tubes, and passes out by the other ; but the water thus introduced is principally for the supply of the gills, — the mouth, or entrance to the stomach, being placed at the other end of the shell, where the mantle is quite open ; and being thus able to take in food from the surrounding water, which comes into free contact with it. The gills in all Lamellibran- chiata consist of four riband-like fringes, fixed to the mantle along the edge of the shell most distant from the hinge. The gills, as well as the interior of the siphons or respiratory tube and the membrane of the mantle, are covered with innumerable minute vibratile cilia, and it is by the agency of these organs that the currents are established in the water, by which the constant change of that element, necessary for the performance of the 400 STRUCTURE OF LAMELLIBRANCHIATA. function of respiration, is effected. In many cases (when the two sides of the mantle are entirely united, except at the respi- ratory openings), the existence of these currents is indispensable Foot Intestine ! Stomach Gills Mantle Anus Respiratory Tubes FIG. 686.— ANATOMY OF AN ACEPHALOUS MOLLUSK. not only for respiration, but also for the nourishment of the ani- mal, as the minute particles of organic matter are separated by the gills, by a sort of filtering process, from the water in which they are floating. According to Messrs. Alder and Hancock, the structure which enables the gills to perform their multifarious GENERAL STRUCTURE OF LAMELLIBRANCHIATA. *393 functions, is as follows : — The branchial laminae consist of numerous delicate tubes running parallel to each other from the base towards the free edge. The walls of these tubes are formed by a network of delicate blood-vessels, through the meshes of which the water bathing the outer surface of the gills is, as it were, filtered into the little tubes permeating their interior, through which it passes into the excurrcnt siphon. Any particles of nutritive matter which may be contained in the water, are arrested by the fine, sieve-like structure of the gills, in the little furrows of the surface of which they are collected into small thread-like masses. These are transferred by the action of the cilia to the grooved edge of the gill, along which they are carried in the same way until they reach the mouth. — Near the middle of the shell is seen the stomach, with the short tube leading to it, the orifice of which (or mouth) is furnished with four tentacula or feelers. To the left of this is seen the long and complicated intestinal tube, with the liver lying in separate masses amongst its folds. Below this is seen the ovarium, in which the eggs are formed; this occupies a large part cf the cavity of the shell during the breeding season. Close to this is the posterior ad- ductor muscle ; by which, with the aid of the anterior muscle situated near the mouth, the valves can be drawn together with considerable force. The intestinal tube is seen to terminate near the opening at the posterior extremity of the shell, in one of the respiratory tubes, which discharges its contents, and serves for the exit of the respiratory current. 1018. The foregoing description will apply, with slight varia- tions, to the structure of almost all Lamellibranchiata ; but we have now to notice two organs, which are absent in some, and in others more largely developed than in the present instance. At the left side of the figure, projecting beyond the edge of the mantle, is seen the foot ; a fleshy muscular organ, somewhat resembling the tongue of higher animals, and not containing any hard support, or protected by any envelope. This foot, which is the only special locomotive organ possessed by the Mollusca of this class, serves a great variety of purposes ; some- times enabling the animal to leap with considerable agility along 394* GENERAL STRUCTURE OF LAMELLIBRANCHIATA. a hard surface, sometimes being used to bore into the sand or mud, and sometimes only serving to affix the animal to some firm support. From the base of this foot there proceeds, in the Mussel and its allies, a band of hair-like filaments, forming what is called the byssus. These sometimes exist in great abundance, and serve, when fixed by their extremities to the shore or bottom of the sea, to anchor the shell, and yet to allow the animal considerable freedom of motion within certain limits. 1019. The Lamellibranchiata have usually more power of lo- comotion than the other Acephala. Some of them, however, are attached to one spot during all but the earliest period of their lives. Others adhere by the byssus, or by the foot, by which they obtain a certain range ; and others are free during the whole of their lives, swimming and leaping with considerable agility. In these movements some of them appeaT to be directed by powers of sight ; and in these small red spots, which are be- lieved to be eyes, are perceived at the edges of the mantle. They do not appear to have much choice of food ; nor are they provided with any other means of obtaining it, than the ciliary action, which introduces constant currents of water into the mouth. In general they do not attain any great size, but they are on the whole larger than any Mollusks except the Cephalo- poda ; and a few species attain considerable dimensions, a Pinna having been met with four feet long, and a Tridacna (Giant Clamp-shell) having been known to weigh 600 Ibs. They are dis- tributed over the whole globe, principally frequenting the shores or shallows. Each region has certain species peculiar to it, or most abundant in it ; and there are few which are not limited to one hemisphere. The temperate zone appears as favourable to the development and multiplication of some species as the torrid zone to others ; but the largest kinds are only found in warm latitudes. 1020. In regard to the subdivision of the Lamellibranchiata into Orders and Families, great difficulty is felt by those by whom this group has been most studied. By some, the presence of a single or double adductor muscle has been taken as the ground of the primary division ; but for the reason already stated, this CLASSIFICATION OF LAMELLIBRANCHIATA. *395 is unsatisfactory (§1016). By others, the degree in which the two divisions, or lobes of the mantle, are united along their edge, is adopted as the foundation of the arrangement ; this also is unsatisfactory for a similar reason, although it is probably a more natural character than the other, because it seems to correspond more with the general structure of the animal. Others, again, have taken the degree of development of the foot as their guide ; but this, too, if followed alone, would lead into many errors. — The fact appears to be, that it is necessary to consider all these characters together, in attempting to make a natural arrangement of this family ; and the Author's recent inquiries regarding the structure of the Shell, lead him to believe that this also will afford a character of great importance, — frequently serving to determine the real position of genera, which would otherwise be doubtful. — Most of recent writers on this .branch of Zoology, have adopted a character nearly coincident with the second of those referred to above, — namely, the presence or absence of siphons, — as the means of establishing two great primary di- visions in this Class. The Orders thus formed, the SIPHONATA and the ASIPHONATA, may be again subdivided into numerous groups distinguished by characters of importance; those here adopted nearly correspond with the families admitted by M. de Blainville. I. The ASIPHONATA, in which the two sides of the mantle are separated, or but slightly adherent at some part of their edges, and in which there is no trace of a siphon or any analogous formation, may be divided into six Sections ; namely : — A. The OSTRACE.E, including the Oysters and their allies. These have the lobes of the mantle open along their whole length, but the body is concealed by the adhesion of the laminae of the gills ; the foot is altogether absent ; and there is but a single adductor muscle. B. The PECTINID^E, or Pectens (Scallop-shells), and their allies, which have, like the last, the lobes of the mantle open ; but the branchial laminae are not adherent ; there is but a single adductor muscle ; and there is usually the rudiment of a foot. 396* CLASSIFICATION OF LAMELLIBRANCHIATA. C. The MARGARITACE^;, or Pearl- Oyster tribe ; these, also, have the edges of the two halves of the mantle, and also of the branchial laminae, free, or not adherent to each other ; and there is but a single adductor muscle ; but the foot is larger, and a byssus is usually present, by which the animals attach them- selves to rocks, &c. D. The MYTILACE^E, or Mussels, which have the lobes of the mantle adherent posteriorly ; the foot small, and provided with a byssus ; and a double adductor muscle, of which the anterior is small. E. The UNIONID^E, or Fresh-water Mussels, which have the mantle non-adherent, but which have the branchial laminae united posteriorly, so as to form a sort of siphon for the exit of water. The foot is a large fleshy mass ; and there is no byssus. In the preceding Orders, the hinge of the shell was very simple ; it now becomes of increased complexity. F. The ARCACE^E, or Arks, which have the mantle but slightly adherent posteriorly, but adherent along the lower edge of the shell : the foot is large ; and there are two adductor muscles, of considerable size. II.- The SIPHONATA have the respiratory orifices distinctly separated from each other, and usually produced into long tubes. The lobes of the mantle are always more or less united. These Mollusks may be arranged in four principal groups, namely : — A. The CHAHACE^E, or Clam-shells, in which the mantle is closed, with a small aperture for the foot, which is very small ; and the respiratory apertures also small and not produced into siphons. The shell is usually very thick, and attached. B. The CARDIACEJE, or Cockles, which also have the mantle closed, with an ample opening for the large and powerful foot ; the siphons are usually short, and the pallial line entire or but slightly sinuated behind. C. The VENERACE^:, with long separate siphons, and a dis- tinctly sinuated pallial line. D. The PHOLADACE^E, with long siphons united throughoi ORDER OSTRACE^E ;— OYSTER. *39/ the whole or the greater part of their length. This group in- cludes the most aberrant forms of the Lamellibranchiate Mol- lusca. OR.DER I.— ASIPHONATA. SECTION A. — OSTRACE^E. • 1021. The shell of the Oyster is formed of two unequal valves, connected together by a hinge on which there are no teeth or ridges, and which is therefore of the simplest character. The shell is attached by the most convex of its valves to rocks, to pieces of wood, and even to others of its own kind. This attachment is formed by the exact adaptation of each layer of shell, prolonged beyond the margin of the former one, to the inequalities of the surface upon which it lies ; and sometimes the margin is actually made to re-curve backwards, to enter some br o 687.— ANATOMY or THE OYSTBR : v, one of the valves of the sht-ll ; t/, itshinfjc ; m, one of the lobes of the mantle ; m', a portion of the other lobe folded back ; e, adduc- tor muscle ; br, gills ; b, mouth , t, tentacula, or prolonged lips ; /, liver ; /, intestine ; a. anus ; co, heart. furrow by which it may hold more firmly. The animal itself is of very simple structure. No vestige of a foot can be seen ; and VOL. II. F F 398* OSTRACE^E ; OYSTERS. the ligament which unites the valves is of small size. On separating the valves, the four rows of gills are observed, form- ing what is called the beard, at a little distance from the fringed edge of the mantle. The adductor muscle is situated at about the centre of the body ; and the heart lies between it and the mass of the viscera, and is easily to be distinguished by the brown colour of its auricle. The mouth is to be found beneath a kind of hood, formed by the* union of the two edges of the mantle near the hinge. The ovaries are of very large size at breeding time ; and one individual produces, according to Poli, 1,200,000 eggs. These eggs appear to be generally developed within the valves of the parent ; so that the young Oysters may be often seen swimming slowly in the fluid surrounding the gills, or attached to these organs. According to Leeuwenhoek, each of these is about 1 -120th of an inch in length ; so that two millions of them closely packed together would not occupy above a cubic inch. He reckoned from 3000 to 4000 to exist in one Oyster at the same time. The principal breeding time of the common Oyster is in April and May, when they cast forth their young in little masses like drops of grease, formed of several united together by an adhesive fluid, upon rocks, stones, or other hard substances that happen to be near ; and to these the spats. as they are termed by fishermen, immediately adhere, soon forming a thin shelly covering. Yery commonly they adhere to adult shells ; and thus are formed the large masses termed banks. Their growth is very rapid. In three months they are larger than a shilling ; and at the end of the first year they have a diameter of two inches. When they are about a year and a half old, they are reckoned fit for the table ; and they are then taken by dredges, and stored in pits, where they undergo changes in their condition, which render them more fit for the market. When removed altogether from their native element, they very commonly open their shells, and lose the water retained between them, which occasions their speedy death ; but if placed in situations which the tide occasionally reaches, they learn to keep their shells closed in the intervals. Although no special organs of sensation can be detected in them, except the tentacula around OSTRACE^E J OYSTERS. *399 the mouth, they are evidently very susceptible of the influence of light, having been observed to close their shells when the shadow of a boat passes over them. 1022. The enormous number of Oysters which exist on our shores, may be best judged of by considering the extent of the banks which they form. These beds occupy portions of the sea, in shallow parts, extending for miles in each direction ; and in some places, the depth of the stratum is very considerable. A remark- able growth of them exists along the alluvial shores of Georgia, in North America ; and their influence in preventing the encroach- ments of the sea is very important. The marsh land extends inwards for a space of from twelve to eighteen miles ; and it is so soft, that an iron rod might be pushed into it without difficulty to the depth of 18 or 20 feet. A great number of large creeks and rivers are found meandering through these marshes ; and the bends of these rivers would in a short time cut through the adjoining land to such an extent, that the whole seaboard would become a quagmire. But wherever the tide directs its destroying force, its effects are counteracted by walls of living oysters, which grow upon each other from the beds of the rivers to the very verge of the banks. These hillocks are often found in bunches among the long grass growing upon the surface of the soil. They are in such abundance, that a vessel of a hundred tons might load herself in three times her own length. These banks are the favourite resort of fish and birds, as well as of the racoon and some other quadrupeds. The neighbouring inhabitants will sometimes light a fire upon the marsh-grass, roll a bunch of oysters upon it, and then eat their contents. This barrier of oysters, like rocks of coral, must offer the strongest resistance to the force of the tide. Such immense collections of shells are very interesting when viewed in relation to Geological pheno- mena; since whole strata of rock are often found entirely composed of shells thus aggregated ; which probably occupied, on the shores of the land then upraised above the surface of the ocean, a position similar to that in which we find the oyster- beds at the present time. 1023. Notwithstanding the enormous number of Oysters 400* OSTRACEJ3 ; — OYSTER ; ANOMIA. which thus accumulate, the race would speedily be extinguished by the voracity with which Man preys upon them, were not the destruction counterbalanced by the powers of multiplication already noticed. But Man is by no means the only enemy to the Oyster. Its body serves as food to many marine animals, which have various methods of getting access to it, in spite of its shelly defence ; from some of these it can secure itself by closing its valves as soon as it is alarmed ; and against others it has a more active means of defence, in the violent expulsion of the water included between them, which (as it is itself fixed) will frequently drive off its opponent. Various animals attack it, also, by perforating its shell ; and to these also it can offer a passive resistance, by depositing new shelly matter within. So that even this lowly-organised being, commonly regarded as one of the most vegetative of animals, is provided by its Creator with such means as are necessary for its preservation, and doubtless also for its enjoyment. 1024. Nearly allied to the Oyster, but having also some points of resemblance to the class of Palliobranchiata or Brachio- poda, is the genus Anomia; which is re- markable for the perforation of one of its valves by a large aperture. This orifice is intended to allow the passage of a peculiar plug, usually more or less calcined, the analogue of the byssus of some other Mollusca, by which the ani- mal adheres to foreign bodies. The valves are thin and of irregular form ; FIG ess— AXOMIA EPHIPPIUM being influenced by the surface on which they grow. They are usually found at- tached to the surface of other shells, especially those of Oysters. 401 SECTION B.-PECTINIDyE. 1025. The Pectens, or Scallop-shells, are known by the regular radiation of the ribs from the summit of each valve to the circum- ference ; and by the two angular projections, or ears, that widen the sides of the hinge. The shell is often very vividly coloured ; and a marked difference in hue is fre- quently observable between the two valves. The animal has a small oval foot ; and some species are attached by a byssus ; whilst others are said to swim freely through the water by the flapping of their valves, and even to regain the sea by a motion of this kind, when left upon the shore. The margin of the mantle bears numerous small black points, which are regarded as eyes. A large species, the Pecten Jacobceus> is the pilgrim's scallop-shell, worn in front of the hat by those who had visited the shrine of St. James at Compostella in Gal- licia. Pectens are sometimes eaten ; but, as the animal is hard and indigestible, few but the poor employ it as an article of food. The hollow valve has been used as a dish ; and even as a culi- nary vessel, being capable of bearing a considerable heat without cracking. — Among other genera of this group, we may notice the Spondylus ; in which the shell bears a general resemblance to that of the Oyster ; but the hinge is provided with two teeth in each valve, which enter into corresponding depressions in the opposite valve. The shell adheres to solid bodies of all kinds ; and its form is modified by the surface of the objects on which it grows. The animal is eaten like the Oyster. The most interesting peculiarity in this genus has been already noticed (§ 942). Many of the species are of very vivid colours. 402 SECTION C.— MARGARITACE^. 1026. This group contains many genera of much interest ; all of them agreeing in the structure of the shell, which is composed internally of nacre, and externally of prismatic cellular substance. The most important is the Avicula ; which receives its name (meaning little bird) from the wing-like projections near the hinge, which are very long in some species (Fig. 690). One spe- cies, the Avicula margaritifera (Fig. 691), produces the most valued Pearls, as well as the greatest quantity of Mother-of- Pearl (the latter being simply the nacreous interior of the shell). The former are separate formations of a similar substance, deposited by the mantle at particular spots, in consequence of some irrita- tion. Various causes will occasion this deposit. If grains of sand find their way between the shell and the mantle, they are generally incrusted by it ; one layer being thrown around another, so that, if the calcareous matter be gradually dissolved FIG. 690.— AVICVLA MACROPTERA. FIG. 691.— AVICULA MARGARITIFERA. away by a weak acid, a series of concentric spheres of membrane remain. Many pearls, however, inclose no such nucleus ; yet still are produced by mechanical irritation of the mantle. It has been observed that, if the shell be penetrated by boring-worms, pearly matter is deposited at the spot perforated ; and an arti- ficial expedient was thus suggested, which has been put in practice with a certain degree of success. This was. to obtain MARGARITACE^l ;— PEARL-FISHERY. 403 the shells, with the animals alive, to make perforations in them, and then to commit them to their native element. The expense of this proceeding, however, has been found to exceed the profit obtained by it ; especially as the pearls thus produced are seldom possessed of that regularity of form, which is an important element in their value. The best pearls are generally produced at the point where the attachment of the adductor muscle causes a roughness in the shell. The gradual change which takes place in the position of this muscle, in accordance with the growth of the animal, causes the detachment of the pearl ; and it is generally found imbedded in the substance of the muscle, by the motion of whose fibres its regularly spherical form seems chiefly occasioned. 1027. The formation of pearls is by no means confined to the Avicula margaritifera. Any shell, univalve or bivalve, with a nacreous interior, may produce them. They have been found in Patellce (Limpets), Haliotides, and Pinnce ; and more especially in the Utiios, which are fresh-water shells, abounding in most rivers of the north.* It is the Pearl Oyster, or Mussel, as it has been termed, which is most sought, as furnishing this com- mercially-important article of luxury. The shell exists in con- siderable banks in the Gulf of Manaar, on the shores of Ceylon, the Persian Gulf, and other parts of the borders of the Indian Ocean ; and also in the Gulf of Panama, and on the east shore of California. It is attached by the byssus to submarine rocks, usually at considerable depths. The most considerable bed is said to occupy a space of twenty miles opposite Condatchy. To prevent injurious destruction, the bank is divided as it were into regular cuts ; one-seventh part being worked every year, so as not to exhaust the bed. The shells are brought up by divers, who, by long practice, acquire the power of remaining under water for four minutes, or even longer ; and in this time they descend to the depth of from four to ten fathoms, pluck the shells from their attachment, and accumulate about fifty in a net sus- * The River Tay in Scotland affords pearls which are held in tolerable esti- mation ; although they are much inferior in clearness and lustre to the ' orient pearl.' From some observations lately published by Professor de Filippi, and Dr. Kuchenmeister, it would appear that in the fresh-water Mussels the form- ation of pearls is often caused by the persistence of the dead ova or cysts of parasitic Worms and Mites in the mantle of the animal. 404 BfARGARITACE^ ; MALLEUS ; PERNA J PINNA. pended from the neck to receive them, and they are then drawn up on giving signal to those above. Each diver can repea this operation about fifty times in one day ; but it is not unco mon to see, after several descents, blood streaming from the n and ears. The shells are laid out that the animals may die ; and when this has taken place (which is known by the opening of the shell) the interior is searched for pearls, and the best shells are set by to furnish mother-of-pearl. The produce of this operation is very considerable. In 1798, the pearl-fishery of Ceylon yielded the sum of 200,000/. ; but the banks seem to have been too much exhausted, as the produce of the subsequent years was much less, and it has not since risen to the same amount. 1028. The Malleus, or Hammer- oyster, is another genus which is chiefly worth notice on account of its singular form ; the two sides of the hinge being extended so as to resemble in some degree the head of a hammer, whilst the valves, elongated nearly at right angles to these, represent the handle. In the Perna the hinge has no teeth, but several parallel depressions opposite to each other in the two valves, and lodging as many small elastic ligaments - Many fossil species of this character, some of them of great size, exist in the Lias, Oolite, and other more recent strata. 1029. The Pinna, or Wing-shell, approaches the Mussels in many respects. It has two equal wedge-shaped valves, united by a ligament along one of their sides ; and is almost entirely composed of the cellular substance formerly described (§ 941). It sometimes attains a considerable size ; measuring as much as two feet in length. The most interesting peculiarity of this genus, is the byssus, which is remarkably long and silky. The animal fixes itself by this to submarine rocks and other bodies ; and lives in a vertical position, the point of the shell being under- most, and the base or edge above. It even attaches its byssus to a sandy or muddy bottom ; and in such situations large troops of them are found at the depth of a few fathoms. The most common species exist in the Mediterranean ; and the inhabitants of Sicily and Calabria seek them, not merely for eating, but to gather the byssus, of which a stuff may be formed that is PINNA. — MYTILACE.E; MUSSELS. 405 remarkable for its suppleness and warmth. The filaments are extremely fine, of perfectly equal diameter through their whole extent, of great strength, and of a brilliant and unalterable red- dish-brown colour. The ancients were acquainted with this sort of stuff; but, in consequence of the diminution in the number oi animals, it is becoming very scarce ; and, from its expensive- ness, it is little more than an object of curiosity. SECTION D.— MYTILACE^. 1030. In all the Mollusks of this Order, there is a foot, which some species employ for locomotion, whilst in others it serves merely to draw out, direct, and fix the byssus. There are also two adductor muscles, of which the anterior one is often very small. The Mussels, properly so called, abound on the rocks of our own coasts, to which they are fixed by their byssus ; and they are often closely impacted together. Although in ordinary circumstances they have no tendency to change of place, they seem possessed of a certain degree of locomotive power. Reau- mur mentions, that in the saline marshes on the sea-coast, where the fishermen throw the Mussels at hazard, they are found at the end of some time united into packets. By putting them into glass vessels, he observed that their mode of progression con- sisted in thrusting their tongue-like foot out of the shell, curving it, hooking it to some adjacent body, and thus drawing them- selves forward to the point of attachment. Vast quantities of them are eaten, principally in the towns on the coasts, and a still larger number is employed for bait ; Dr. Knapp states that for the latter purpose from 30 to 40 millions are annually collected in the Frith of Forth alone. Although Mussels commonly afford a very wholesome supply of food, they sometimes acquire very poisonous properties. How this is to be accounted for, is yet uncertain. Many instances have occurred, in which a large number of persons have been suddenly attacked with violent symptoms, after eating Mussels from a particular bed ; and fatal. 406 MYTILACE2E ;— LITHODOMI ; DREISSENA. cases have not been uncommon. Whilst Mussels in general attach themselves to the surface of rocks, &c., others appear to seek out hollows, and imbed themselves there. Others form ex- cavations for themselves in mud ; and are found in spots which are occasionally left dry by the tide. 1031. The Lithodomi are endowed with the power of per-" forating stone and masses of coral, as well as large shells of other Mollusca. In the earlier stages of life, it is stated by Cuvier, the Lithodomi suspend themselves by their byssus ; but when they have pierced the bodies to which they are attached, and introduced themselves into the cavity, the byssus disappears. The excavation does not seem to be here produced by the mechanical action of the shell, which is not adapted for such an office. Nor is there any reason to believe that it is occasioned by a solvent fluid secreted by the animal. It is attributed by Mr. Garner principally to the currents of water constantly im- pelled against the rock by the vibration of the cilia ; and in this supposition there is much probability. — The lithodome Mussels, as well as others, are used as food where they abound ; and means have been taken on some parts of the coast to cause them to multiply. As with Oysters, it appears that the Mussels are rendered more tender, and the quality of their flesh improved, by putting them in places where the saltness of the sea-water is tempered by rain or river-water. Accordingly, on the coasts of France and Italy, regular breeding-places have been estab- lished, where those which have been obtained from the sea are cast for a time to improve their quality, and where also the spawn is reared ; these are so arranged as to communicate with the sea, but to allow the intermixture of fresh water at pleasure. 1032. A Mollusk allied to the Mussel, the Dreissena poly- morpha, has been recently introduced into this country ; and affords an interesting example of the complete naturalisation and rapid multiplication of a foreign species. This is evidently due to the variety of circumstances under which it can exist. It is found abundantly in the Black Sea, the Baltic, and other inland seas ; and it lives, like the Mussel, in aggregated masses, attached to the bottom by the byssus. It is also found in many of the DREISSENA.— UNIONID^. 407 large Continental rivers, such as the Danube, the Wolga, and the Rhine. It was first discovered in England in 1824, in the Commercial Docks of London, where it was probably conveyed with some timber ; and it has since diffused itself through the rivers and canals of the whole island. This may be partly ac- complished by its adhesion to the keels of boats. The young even pass through the pipes laid down for. the supply of water and thus make their appearance most unexpectedly in tanks, &c. SECTION E.— UNIONID^E. 1033. The Mollusks of this Order, frequently called Fresh- water Mussels, are for the most part included in the genera Anodon and Unto. The former is named from the absence of teeth in the hinge, which has merely a ligament along its entire length. The ani- mals are without a byssus ; and creep over the sand or mud by means of their large foot, which has three layers of fibres disposed in different direc- tions, so that it has considerable power of altering its form and di- FIG. 692.-ANODONBIPSA8. mensions. They are most commonly found sunk in mud, however, with that part of the aperture of the shell which corresponds to the mouth directed upwards. It has been said that they have some power of swimming, by striking the water with their valves. The Anodon is viviparous, the eggs being hatched within the shell ; and thousands of young ones may be seen in the winter, with a 408 UNIO.— ARCACE.E. microscope, dispersed among the gills, and opening and closing their shells. Dr. Lea has calculated that as many as 600,000 young are contained in the outer gills of a single female. — The Unio resembles the Anodon in the structure of the shell, and the conformation of the animal ; except that the hinge is more complicated. There is a short plate in the left valve, received into a cavity in the right ; and behind this a longer plate clos- ing between two others of the opposite side. These, like the Anodontes, inhabit fresh water, preferring running streams. Several are natives of this country ; but they especially abound in the rivers and lakes of North America. The abundance of their nacreous lining causes it sometimes to be employed for the purposes to which mother-of-pearl is applied ; and pearls are occasionally obtained from them (§ 1027). The animal is of no value as food, from the insipidity of its taste. SECTION R— ARCACE^E. 1034. The Area is distinguished b'y its equivalve shell, and FIG. 693.— ARCA BARBATA AND ARCA NO.B. by the long line formed by the hinge, which is studded with minute teeth. The valves, which are covered with a strong epidermis, do not always meet in the middle ; but a space is often left for the passage of a horny, apparently tendinous substance, which takes the place of the byssus, arid by which the animals are affixed to submarine bodies. They reside near the shore in rocky places. Numerous species are distributed in all parts of ARCA ; PECTUNCULUS.— CHAMACEJ2. 409 TIG. 694 — PECTUNCULTJS. the world, but their remains are far more abundant in many of the older strata. — In the Pectunculus the hinge has a similar elongated character, but it is curved instead of being straight. — The Tri- gonice are closely allied to the Arks, but differ from them in having only two or three teeth in the hinge. The foot is long and bent, and is said to enable them to leap with con- siderable activity. The few living species are confined to the Australian seas. ORDER IL— SIPHONATA. SECTION A. — CHAMACE^E. 1035. In this group are included the largest, and some of the most inert, of all the Testa- ceous Mollusca. Nearly all of them are attached to solid bodies, during the greatest part of their lives ; some by the adhesion of the shell itself, and others by a tendinous prolongation of the foot, which serves as a byssus. The shell is generally irregular form, in consequence €f these adhesions ; its hinge is very analogous to that of Unio, the left valve being provided with a tooth, and further back with a projecting plate, received into corresponding cavities in the right valve. The foot is generally small, and the adductor muscle is double, the anterior one, however, being sometimes rudi- mentary.— The Chama is attached by the shell itself to rocks, corals, and even to masses of similar shells, in the manner of Oysters; and the individuals are thus cemented so strongly to Fir,. 695. — CHAMA, with the shell remoTed, to show the arrangement of the mantle and its orifices. The two lobes are adherent along their entire edges ; except at the respiratory passages, r and «, and to give exit to the foot,/. 410 CHAMACKE ; — CHAMA, TRIDACNA, each other, that they cannot be detached without breaking the shells. These are subject to changes not only of shape but of colour, in accordance with the accidents of their position. The attached valve is very irregular, and takes the form of the surface to which it is applied ; and it is usually much less coloured than the other. The valves have a series of foliations, or leaf-like projections, on their surface; and the luxuriancy of these depends upon the stillness of the medium in which the animal exists. If it inhabit deep and placid water, the expansions will generally be of con- siderable size ; whilst those of the individual that has borne the buffetting of a comparatively shallow and turbulent sea, will be poor and stunted. This genus is confined to the warmer seas ; the Mediterranean being the locality of the lowest temperature where any species have been hitherto found ; the shells have been observed at various depths, ranging from points near the surface to seventeen fathoms. 1036. The Tridacna, of which one species is the largest knowc Conchiferous Mollusk, is still more restricted to warm localities ; the East Indian and Australian seas alone supplying specimens of it. This is readily distinguished from the Chama by the equality of the valves ; since, instead of being fixed by the adhe- ..sion of one of these, it is attached, during part of its life at least, by a tendinous byssus that passes out through a channel in the anterior part of the mantle, which forms a well-marked groove in the shell. The Tridacna, or Giant Clam-shell, sometimes attains an enormous weight as well as dimension. There is a pair in the Church of St. Sulpice at Paris, which are used as " Benitiers" (receptacles for holy- water), and weigh more than 500 pounds ; Lamarck mentions a specimen in which each valve measured three feet by two ; so that the story of an oyster which furnished a dinner to a FIG. 696.— TRIDACNA. TRIDACNA. CARDIACE.E. 411 whole regiment is scarcely an exaggeration, as the flesh of these animals is commonly used as food where they abound, and is by no means unpalatable. The remarkable difference of the shell of this animal at different epochs of its growth, has given rise to the formation of many species which have no real existence. It is only when immature, and when the shell is comparatively light, that the animal is attached by a byssus. This cord, how- ever, seems rather to be a musculo-tendinous prolongation of the foot itself, than a fibrous tissue secreted by it like the byssus of the Pinna ; it is so tough as to require to be chopped with a hat- chet, in order that the shell may be detached. As the animal approaches adult age, however, and has by successive layers very much increased the weight of the shell, the byssus, being no longer required to secure it from injury, disappears, and the groove in the shell is filled up with a solid deposit. When thus free, it is said to be taken with a long pole, which is introduced between the valves when open ; the animal immediately closes the valves upon it, and does not quit its hold until it is landed. In some of the numerous and remarkable fossil species of this sec- tion, one or both of the valves are spiral. SECTION B.— CARDIACS^. 1037. This Order, including the Cockles and their allies, con- tains several genera, which, in the smallness and delicacy of many of their shells, and in the comparative activity of the animals that form and inhabit them, offer a remarkable contrast to those of the previous group. The shells are all equivalve, or nearly so ; they are furnished with a regularly-toothed hinge, often of great complexity and beauty ; and there is always a double adductor muscle. The foot is here more largely de- veloped than in any of the previous Orders, and it is a very im- portant organ to the animals, not only serving to excavate bur- rows in the sand or mud of the sea-bottom, but also enabling its possessors to leap with considerable agility. In some cases also it forms a creeping disc. The respiratory orifices are prolonged 412 CARDIACE^l; — CARDIUM, OR COCKLE. into tubes ; which can, however, be drawn within the shell by means of a retractor muscle ; but the siphons are usually short, and the pallial line is never more than slightly sinuated behind. 1038. In the Cardium, or Cockle, the tubes or siphons are shorter than in most of the other genera ; indeed they are some- times reduced to mere openings ; and scarcely any vestige of a retractor muscle exists. The foot is very large, and is capable of being bent at an acute angle, and then suddenly straightened ; so as to enable the animal to move from place to place by a succes- sion of leaps. But it is only occasionally that it serves this pur- pose. The chief use of the organ is as a boring instrument, by which the animal may penetrate the sand or mud, below the sur- face of which it is usually found. A very curious provision exists for adapting it to this object. As usually seen, the foot, when extended, tapers gradually to a point ; and as its diameter at its largest point is much less than the breadth of the shell, it is not apparent by what means the hole that is excavated is made sufficiently large for the reception of the latter. This is accom- plished, however, by the distension of the foot with water, through a tube which opens just within the mouth ; and thus the size of the bojer becomes so nearly equal to that of the shell, that (its solid point first entering the sand) it is enabled, by rotatory motions often repeated, to excavate a burrow large enough to receive the animal with its shell. The Cardia are found in all known seas ; and in some they abound so much, that they become very important articles of food to Man, as well as to marine animals. Mr. Kirby mentions that, on the North-East coast of Norfolk, an alteration in the sands has taken place, which has caused a great diminution of late years in the number of boring bivalves : and that the quantity of Soles and other Flat Fish frequenting the coast, of which they form the principal food, has consequently much decreased also. 413 SECTION C.— VENERACE^E. 1039. The Veneraceae closely resemble the Cockles in many points of their structure, but their siphons are always greatly elongated (Fig. 697), and furnished with well-developed muscles for their retraction, which are indicated in the interior of the shell by the deep sinuation of ~^H *^e Posteri°r portion of the pal- compressed, and no. 8.7.-TELLIXA. ?sua% more or less triangular J it is employed principally as an agent in burrowing. This group includes a considerable num- ber of genera of great interest to the Conchologist ; many of them being remarkable for the beauty of their shells, or for the curious situations in which they live. The greater number of them inhabit sand or mud; but there are several which bore into rocks ; and a few that burrow in masses of coral. The means by which the latter make their excavations are not under- stood. The resemblance both in the shell and the animal, among these numerous genera, is often so strong, as to produce a diffi- culty in their classification, as well as to render it unnecessary to enter here into details respecting them. It will be sufficient to name the genera, Venus, Cytherea, Mactra, Tellina, Donax, Petricola, and Venerupis, as including the greatest proportion of the group ; these being names with which even the ordinary §hell- Collector must soon become familiar, on account of the large proportion that the bivalves of this group bear to others, on almost every coast. SECTION D.— PHOLADACE^. 1040. The Mollusks of this group are distinguished from those of the preceding, by the wide gape of their shells at the poste- VOL. II. G G 414 PHOLADACE^; SOLEN. rior extremity, and by the length and union of the respiratory tubes. Their habit is to burrow much more deeply ; and their foot is made to project rather from the anterior extremity, than from the middle of the body ; so that the form of the whole is more cylindrical than we have yet seen it. The Solen, or Razor- shell, is a well-known example of this group. It has an elongated shell of which the hinge is furnished with distinct teeth, and the ligament is altogether external. The animal burrows in the sand, into which it sinks rapidly on the approach of danger. It seldom or never quits its hole ; and its movements are nearly limited, therefore, to an ascent or descent in it. This it ac- complishes by means of its foot, which it elongates and at- tenuates into a point, when it wishes to bore ; contracting it into a rounded form, so as to fix it by its enlargement within the hole, when it desires to rise. The animal is sought for by fishermen on some coasts, as a bait for certain fish. Its burrow is often recognised by the little jet of water which the animal throws out, when alarmed by the shaking of the sand occasioned by the motion of the fisherman above. When the tide is low,: the holes are often seen in considerable numbers ; and this is also the time when the animal may be most easily procured. The fisherman throws a little salt upon the hole, which induces the animal to ascend, according to some, by leading it to the belief that the tide had returned, — and, according to others, by an irritating effect of which it desires to get rid. To seize it when it makes its appearance, some address and quickness are required ; for it speedily returns to its burrow ; and, if entrapped, its struggles are sufficiently powerful to cause injury by the sharp edges of the shells. If it re-enter its hole, fresh pinches of salt no longer produce the same effect ; the animal having either learned by experience that they do not indicate the return of the sea above it, or deeming it better to submit to the irritation than to expose itself to capture. The fisherman then has recourse to a long iron crook, which he sinks pretty deeply ; and, drawing it out obliquely, carries away the sand, and the Solen contained in it. If he should fail in this attempt, he knows that to try again would be useless ; since the animal instantly burrows MYA; SAXICAVA; PHOLAS. 415 rapidly down to such a distance, as to render pursuit of this kind useless. 1041. This group is connected with the preceding by the Mya, Lutraria, and other genera, which are common on our coasts ; and which burrow into sand or mud. Mya arenaria, and M. truncata, are found abundantly in the sand all round our coasts ; the former, which is the largest, often burrows to the depth of a foot. Their siphons are very long. Some, such as the Saxicava, burrow in rocks. 1042. The remaining members of this group are amongst the most interesting of the Bivalve Mollusca, both as regards their habits and the curious varieties of structure which they present The valves of the shell never cover the whole surface of the ani- mal, and the branchial siphons are always exposed. They bur- row not only in sand or mud, but also in wood and rock. In the Pholas, which presents the greatest resemblance to the ordi- nary Bivalves, the shell is formed of two principal valves, which leave a considerable space between them at each end when they are closed ; and of supernumerary pieces, the number and position of which vary considerably. The foot issues at the opening through the larger end ; and the respiratory siphons, which are very long and extensible, pass out by the other. Some Pholades form their cells in mud or clay ; but many in rocks, and others in wood. It is evident that a fleshy foot can be of little use in the ex- cavation of a stony mass ; and the organ here appears to serve a different purpose. The boring operation seems to be performed by the shell itself, which has a rasp-like surface, and which is renewed by vital action as fast as it is worn down. In order to make the valves rotate backwards and forwards (like a surgeon's trephine), the foot is affixed to the bottom or end of the hole, and becomes a fixed point from which the muscles can act. They seem to commence this operation almost as soon as they quit the egg ; the young beginning to bore the rock on which they are cast, and enlarging their cell, which they never volun- tarily quit, in accordance with their own increase in size. They possess a very curious means of freeing the tube from the rasp- ings of the rock produced by their penetration. The siphon 416 PHOLADACE;E ; — PHOLAS, TEREDO. being distended with water, the animal suddenly contracts it ; and thus a jet is produced through the anterior orifice, which washes out the part of the cavity occupied by the animal ; but, as many of the particles expelled by it are deposited before they reach the mouth of the hole, the passage is found to be lined nearer its entrance with a soft mud. 1043. The Pholades evidently prefer such beds, as are com- posed of indurated clay, or soft lime-stones, to harder lime-stones ; though they are occasionally found in the latter. Hence it might be supposed that their action is always of the mechanical nature just described ; but though it is certainly of this kind in many instances (as is proved by the cylindrical form of the perforation, as also by the rasp-marks on its interior), Pholades are some- times found so imbedded, that they could not have turned in their perforation. — In some countries they are much prized as food; especially along the Mediterranean coast. They possess one remarkable property, which is not, however, confined to them, but which is manifested in a degree by other Mollusca ; this is their phosphorescence. It is said to be so strong, that persons who eat them raw, and in an obscure or dark place, seem to be swallowing phosphorus. The Pholades are pretty generally diffused over the globe. They usually multiply around any spot which they have begun to frequent ; the young produced from the eggs probably boring near their parents. Pholades are not very abundant in a fossil state ; but they are occasionally found in tertiary strata, imbedded in the cavities which they have themselves formed. 1044. The Teredo is a genus which presents many points of interest to the Naturalist, as well as to those who are practically affected by its destructive operations. This animal bears a general resemblance to the Pholas ; and it carries on its anterior part a pair of valves, which it uses in the same manner, as perforators of the wood into which it bores. "When quite young, it establishes its habitation in submerged timber, such as ships' bottoms, piles, &c., which it perforates in every direction. With its increasing bulk, it enlarges its hole, advancing into the wood ; but it does not draw the tubes of the mantle after it, for they remain where they were, and deposit shelly matter, which PHOLADACEJE J TEREDO OR WOOD-WORM. 417 lines the cavity ; and thus a complete additional tube of shell is formed, of a length proportional to the age of the animal.* At the entrance of the tube, or the termination of the siphons, there is a pair of pallettes, or small valves of shelly structure ; by the motion of which the current of water is maintained, that is necessary to bring a supply of food and oxygen to the animal thus included. The highest point at which they commence to bore, is always some feet below the lowest water-mark ; and they usually work downwards. The orifice, being made when the animal was young, is very small, and often difficult to perceive. The beginning of the tube is usually horizontal or oblique ; and afterwards it curves into a nearly vertical direction. The nature of the wood has a great influence on the regularity and direction of the canal which is hollowed in its interior ; but this is still more affected by the neighbourhood of other Teredines, to avoid whose tubes the animal will make sudden curves. It is difficult to comprehend how it can become conscious of their proximity. There can be no doubt that, in this instance, the excavation is effected by the valves ; since it is always cylindrical, with very smooth walls ; and the shell is adapted, both by its sides and edges, for rasping and boring. 1045. These animals are among the most formidable destroyers of the works of Man. When it is considered that their instinct prompts them to attack all the timber which he has, for various objects, placed beneath the surface of the sea, it is seen that the field of their operation is immense. The piles of bridges, piers, and harbours, as well as shipping, are liable to their devastations ; and Holland has been more than once threatened with an inun- dation, by the destruction of the dykes which they have effected. Many vessels have sprung . leaks and foundered, owing to the unsuspected demolition, of the planking of their bottoms by the same means. The most effectual protection against their attacks, is a metallic sheathing : but it is said that piles may be secured by the previous charring ot their surface to the depth of a few lines. Different species of Teredo appear to exist in all • The accessory pieces of the shell of the Pholas, may probably be considered as a rudiment of the same structure ; they vary considerably in number and amusement ; and sometimes appear to form the commencement of a regular tube. 418 I'HOLADACEJE ;— GASTROCH2ENA, CLAVAGELLA, ASPERGILLUM:. parts of the world ; and on the coasts of the Atlantic they are used as food, their flesh being reputed more delicate than that of Oysters. According to Seba, who made his observations in Holland, certain species of Nereis (§ 910) are mortal enemies to the Teredines, penetrating into their tubes and devouring them. As a British animal, the Teredo is now nearly or quite extinct ; the precautions taken against it having prevented its multiplica- tion : and new importations being checked by the general use of copper sheathing. 1046. In the Gastrochcena, the valves bear a still smaller proportion to the shelly tube, which not only covers the part of the excavation posterior to the animal, but lines the whole inte- rior 01 the hollow, so as to include the valves. This tube is often found in the perforations previously made by some other boring Mollusk, and also in natural hollows in rocks, corals, &c. ; but the animal has evidently the power of exca- vating for itself, if it does not meet with a hole adapted to it. — The Clavagella is an animal of analogous structure ; but one of its valves is incorporated, as it were, with the shelly tube, the other remaining free. The latter appears to perform by its movements the same kind of function as the pallettes of the Teredo. — The Aspergillum departs more widely from the general type, than any of the preceding ; so that, if viewed out of con- nexion with them, its true place in the scale would be doubtful. The shell, which derives its name from its resemblance to the spout of a watering-pot, has the form of an elongated oone, terminating at the large end in a disk, which is pierced with a number of tubular orifices ; and the tubes of the outer row being the longest, they form a sort of corolla la, Fig. 698) around the disk. At a little distance above this, two small valves (Z>), in- corporated in the substance of the tube, are easily distinguished. The smaller end is open, and there is likewise a little fissure Fro. 698- — ASPBR- OILLUW. ASPERGILLUM. — GEOLOGICAL DISTRIBUTION. 419 nearer the larger end ; by these apertures the water is freely admitted to the interior of the shell. The animals of this genus are borers. Some of them live in the sand, plunged down per- pendicularly for about three-fourths of their length, and sup- ported by the little tubular prolongations, which are supposed to be filled by fleshy filaments of the mantle. Some, again, burrow in stone, others in wood, and others in thick shells. 1047. In regard to the Geological distribution of the Lamelli- branchiata, it will be sufficient (as in the case of the Gasteropoda) to say, that they make their appearance in the earliest fossili- ferous strata ; and that, although there is always a difference between the fossil and the existing species, until we compare those of the comparatively recent geological periods, the same genera are found to have existed in the ocean, from very ancient times to the present. It is interesting to remark, however, that the proportion which they bore to the Bivalves of the succeed- ing class, was very small in the oldest fossiliferous rocks, but haa since been gradually reversed. 420 CHAPTER XIX. OF THE CLASS OF PALLIOBRANCHIATA. 1048. THIS Class, although at present very limited, — both as to the number of existing species it includes, and the small num- ber of these which seem to be distributed through the ocean, — was formerly of great importance ; since it included a very large proportion of the Bivalve Mollusks of the older rocks. Although an ordinary observer would not detect anything in the structure of the shell, to justify the separation of this Class as distinct from the preceding, yet the necessity for this division becomes evident, when the organisation of the animal is examined. The valves of the shell differ completely in their position from those of the preceding Class, being placed upon the upper and lower surface of the animal, instead of on its sides. The substance of the shell itself is also peculiar, being perforated in nearly all the species by an immense number of minute apertures, passing perpendicu- larly from the inner to the outer surface. These are filled by minute processes of the mantle. The name of the Class is de- rived from the peculiar conformation of the respiratory appara- tus, which here consists of the mantle itself ; this is traversed by blood-vessels which ramify minutely over its surface ; and is furnished, especially along its edge, with vibratile cilia, which produce a continual current in the surrounding water, and thus renew it for the aeration of the circulating fluid. In addition to this singularity of structure, the organs for procuring food offer remarkable peculiarities. They consist of two long spiral arms, one on each side of the mouth ; the existence of which has given rise to the name BRACHIOPODA, or Arm-footed, by which the class is frequently designated. In many species, these are capa- ble of not only being unrolled, but extended beyond the shell to a great distance in quest of food. They are usually furnished with PALLIOBRANCHIATA ; GENERAL CHARACTERS. 421 numerous vibratory filaments, for the more certain capture of the prey, and probably also for assisting in the maintenance of the respiratory current — an extraordinary provision, which is ren- dered necessary by the great depth at which these animals live, and the consequent enormous pressure of the water around. All the existing genera of this Class are attached, in some way or other, to solid bodies. In Terebratula and Lingula, this attach- ment is effected by means of a fleshy tubular footstalk ; and this footstalk or peduncle passes out, in the Terebratula and its allies, through an aperture or notch in the beak of the lower valve of the shell (Fig. 700). In Crania and its allies, on the contrary, FIG. 699.— RHYNCHONELLA P8ITTACEA. FIG. 700. — LOWER VALVE OF TEREBRATULA. the peduncle is wanting : and the lower valve of the shell itself becomes the medium by which the attachment of the animal to the rock is accomplished. There is thus the same kind of dif- ference between these genera, as between the pedunculated and sessile Cirrhopods, — a group, of which we are also strongly reminded by the structure of the arms of the Brachiopoda. 1049. The valves of the shell in the Palliobranchiata are usually unequal, the lower (or ventral) valve being almost always the largest, and projecting in the form of a beak beyond the upper (or dorsal) valve. In this beak is situated the aperture through which the footstalk passes. The hinge is generally formed by a pair of teeth, springing from the ventral valve and fitting into corresponding cavities in the dorsal valve ; there is no ligament, and the valves are opened and closed by a very complicated arrangement of muscles. The interior of the dorsal valve very frequently bears a curious calcareous framework, 422 PALLIOBRANCHIATA ;— TEREBRATULIDJE. which serves for the support of the fringed spiral arms already alluded to. The body of the animal, containing the viscera, occupies but a small portion of the interior of the shell, and is placed quite at the hinder portion of this cavity. In most cases the intestine, which is convoluted, has no anal aperture. These Mollusks have generally been described as possessing two or four hearts, but according to the recent researches of Professor Hux- ley, and Mr. A. Hancock, the organs which have been indicated as hearts open into the cavity of the mantle, and probably serve for the passage of the ova. The true heart is a pyriform organ at- tached to the stomach. The circulation of the blood is effected by a complicated system of vessels and lacunae, permeating all parts of the body and mantle ; and there is also a system of aquiferous canals, communicating with the chamber enclosing the viscera, into which the water probably enters through the organs above alluded to as having been regarded as hearts. 1050. The greater part of the existing Mollusks included in this Class, belong to the Family TEREBRATULIDVE, of which about fifty species are at present known to exist, but of which several hundred fossil species have been enumerated. These present themselves in the very oldest rocks ; and may be found, in greater or less abundance, in almost all marine deposits, down to the present time. They possess the peculiar characters above described in the fullest perfection, — the two valves are unequal, and usually united by a toothed hinge ; the lower valve is large, convex, beaked, and perforated at the beak for the passage of the peduncle ; and the upper valve is provided with a slender frame- work of shelly substance for the support of the arms. This framework is often found in fossil shells, in a beautiful state of preservation. The arms of the ordinary Terebratulse do not ap- pear to be extensible beyond the shell ; but in the Rhynchonella psittacea they are enormously developed ; and being quite free except at their origin, they may be extended far beyond the shell. When drawn in, they are disposed in six or se v< n spiral turns. The mechanism by which these arms are said to be unfolded is very curious. The stem of each is tubular, and contains a fluid, which, being acted upon by muscles forming the walls of PRODUCTIVE ;— CRANIID^E ;— DISCINID^. 423 the canal, is forced onwards up the tube, and thus causes the arm to project. We shall hereafter meet with a similar con- trivance, in the tubular feet of the Echinodermata (§ 1097). The Terebratulida? are found in all seas, from the polar to the equinoctial, at a depth of from ten to ninety fathoms, or even more. 105 1. The PRODUCTIVE, which are only known in a fossil state, appear to have been generally unattached, and their valves .are united by a long hinge-line, which however is destitute of teeth. They are remarkable for the form of their shells, the lower valve being convex, and the upper concave externally ; so that the entire shell forms a concavo-convex figure, and the inner surfaces of the two valves are brought very close together. They are often armed with spines along the hinge-margin. — The CIIANIID^E, of which several species are still in existence, have neither a hinge nor a peduncle, but the shells are attached by the lower valve. The dorsal valve is the largest, convex, and limpet-like ; and the interior of both valves exhibits a broad granulated border, and four large muscular impressions. — In the DISCINID^E, which are nearly allied to the preceding, the two valves also differ considerably in form and size ; the upper one being conical and rounded, like the shell of the Limpet (with which it was formerly confounded), whilst the other is flat, with a fissure near the centre for the passage of a ligament, by means of which it is fixed to the rocks. The Mollusk has ciliated arms, rolled up spirally when withdrawn, and the mantle is fringed all round with long horny bristles. The recent species of this genus are found attached to stones, shells, and sunken wrecks, at various depths, down to seventeen fathoms. 1052. In the Family LINGULIDJE, the animal is attached by a peduncle, which is often of considerable length, but which issues from between the valves of the shell at the hinge-margin, and not through an aperture. The valves are of a more or less horny texture, nearly equal, and destitute of hinge-teeth ; and the mantle is fringed with horny bristles. The recent species all belong to the genus Lingula, so called from the resemblance in the shape of their shells to a tongue ; they are found in shallow water, on the shores of the Indian and Pacific Oceans. 424 CHAPTER XX. OF THE CLASS OF TUNlCATA. 1053. ALTHOUGH the Mollusca are in general possessed of a calcareous shell, sometimes enveloping the whole body, and sometimes enclosing but a small portion of it, no appearance of such a structure is presented among the animals of the present group, — the Class TUNICATA. Feeble as are the powers of sensation and locomotion in a great proportion of the Molluscous tribes, they would seem almost extinct among the members of this group. The greater number of them pass their whole lives in one situation, agglutinated by their external tunic to submarine rocks, or attached by a footstalk prolonged from it ; many species associate together, like the Polypifera, to form a compound structure, in which several individuals are united more or less closely ; and those which have no fixed attachment enjoy little independent locomotive power, but are driven about at the mercy of the waves. No beings possessed of a complex internal structure, a distinct stomach and alimentary tube, a pulsating heart and ramifying vascular apparatus, with branchial append- ages for aerating the blood, and highly-developed secretory and reproductive organs, can be imagined to spend the period of their existence in a mode more completely vegetative than these. 1054. The animals of this Class are entirely enveloped in a firm elastic tunic (whence their name), which is always provided with two orifices. The general form of the body, as well as the colour and consistence of this tunic, vafy considerably in the different species. Sometimes it is globular or egg-shaped ; some- times narrow and prolonged. The tunic is often of leathery or even cartilaginous firmness, and of a dark colour ; whilst we occasionally find it soft, membranous, and transparent, and of a light greenish tint, so that the clusters of animals look like GENERAL STRUCTURE OF TUNICATA. 425 bunches of grapes. In the larger species, additional firmness is often given to this tunic, by the agglutination of particles of sand, bits of gravel- or shell, or other substances with which it conies in contact, to its exterior ; and a complete envelope is sometimes formed in this manner, which might be compared to the shells of the higher Mollusca, but that it is altogether derived from external sources, — the glutinous matter which unites the parti- cles together, being the only part furnished by the animal itself. 1055. Within the external tunic is a second coat, or inner tunic, which is continuous with the outer coat at the apertures, but is separated from it by a considerable space throughout the rest of the body. The inner tunic is furnished with muscular bands, which vary in number and direction, by which compres- sion may be exercised upon the contents of the cavity which it surrounds. The space between the two tunics is filled up with a system of sinuses, serving for the circulation of the blood ; and the cavity enclosed by the inner tunic, which is open at both ends, is constantly filled with water, which thus comes in sufficient contact with the blood to effect the function of respir- ation. This inner cavity is consequently to be regarded as a respiratory sac. The function of respiration is performed in part through the membrane of the inner tunic itself; but there is usually a further provision for this purpose in the form either of a band, running from end to end of the respiratory cavity, or of a network of filaments attached to the inner tunic ; both these forms of respiratory organs are clothed with cilia. 1056. The entrance to the digestive tube lies at the posterior portion of the respiratory sac ; and the alimentary particles are derived from the water introduced into the latter for the purpose of respiration. The resophagus is short, and leads to a capacious stomach surrounded by clusters of biliary follicles (ANIM. PHYS. § 356), the rudimentary form of a liver. The intestine generally makes one or two turns in the space between the branchial sac and the mantle ; and terminates in the neighbourhood of the posterior funnel. The ovaria are usually large, and lie amongst the viscera ; their excretory duct also terminates in the same situation. The posterior funnel thus serves to carry out of the 426 GENERAL STRUCTURE OF TUNICATA. cavity of the mantle, not only the fluid stream which has passed over the walls of the branchial sac, and has served its purpose in aerating the blood, but also the solid particles which are rejected from the alimentary canal, and the ova which are discharged, when mature, from the ovaria. The heart, which is usually situated close to the digestive organs, is of a more or less tubular form ; and the circulation of the blood is effected by the progressive contraction of the walls of the heart from one end to the other. The circulation, however, differs in a most re- markable manner from that of all other animals. Instead of circulating constantly in one direction, the blood is driven out of the heart continuously towards one part of the body for a certain time ; the contractions of the heart then cease, and after a short repose, recommence in a direction opposite to the former one. 1057. Between the two orifices there is a nervous ganglion, which sends filaments to each of them, and distributes its principal branches over the general surface of the mantle. No organs of special sensation, however, are perceptible ; except the rudi- ments of an auditory organ in some species ; and the only indication of common sensi- bility shown by these animals, is the con- traction of the mantle when they are touched, by which the water contained in the bran- chjai sac is spirted out, sometimes to a con- 7 siderable distance. Sometimes a number of them are so closely impacted together on the rocks> that the impression given to one causes it suddenly to retract, which acts also on the one next to it, and so on throughout several of them ; and each in contracting throws out a quantity of water. After the contracting force has ceased to operate, the usual form is re- stored by the elasticity of the tunic. 1058. In many cases, however, no regular movements of this kind are commonly employed, either for the respiratory pro- cess, or for the prehension of food. A continuous and equable FIG. 701. -NERVOUS SYS- TEM OF ASCIDIA : «, branchial orifice or uo°nTi mlntie (t'heT- move!) C°at being "" ' GENERAL CHARACTERS OF TUNICATA. 427 current of water enters the branchial orifice, and is propelled through the funnel, without any other physical agency that can. be perceived, than the vibration of the cilia which cover the aerating surface. It is from the contractions of the muscles of the inner tunic, that the unattached species appear to derive the slight amount of independent locomotive power which they possess. In these, the two orifices are usually at the opposite extremities of the body ; and the continual suction of water into one end, and the discharge of it from the other, will of course tend to propel the body forwards. This movement is most evident when several are associated together, all having their branchial orifices, and funnels in the same direction. In the Pyrosoma (§ 1065), a number adhere together so as to form a tube closed at one end, into the interior of which the funnels of all the individuals open ; whilst the branchial orifices project from the outside as so many little papillas. The water drawn in through these is discharged into the central canal ; from the end of which a constant stream issues, with sufficient power to cause the movement of the mass in the opposite direction, — a movement which its brilliant phos- phorescence allows to be watched from some distance. 1059. Although the Tunicata have been variously placed by different Naturalists, the additions which have been recently made to our knowledge of their organisation leave no doubt that their true place is on the border of the Sub-Kingdom Mollusca, connecting it with the Radiata. For, whilst the higher species present many points of resemblance to the lower forms of the Conchifera, the inferior tribes approach equally closely to the Polypifera, — not only through the structure of the individuals, but in the examples they present of the union of a number of independent beings to form a compound animal. So prevalent, indeed, is the tendency to this association, that it may almost be regarded as the peculiar character of the group ; and, when thus viewed, it presents a very good illustration of the general principle formerly laid down (§ 42, 43). We may regard the Tunicata, then, as an aberrant group of Mollusca;' engrafting, as it were, upon the general character of that Sub-Kingdom, the peculiar tendency of the group of Radiata towards which it verges. The 428 SUBDIVISIONS OP TUNICATA. tendency to aggregation exhibits itself among the Tunicata in various ways. Sometimes we find a number of individuals simply adhering externally, but forming a mass of a certain regular aspect. In other cases, we observe several individuals included within a common envelope, — their own external coats being absent. And in some instances, there is a continuous cir- culation of blood among several individuals, through vessels passing along a stem, with which they are all connected by short peduncles or foot-stalks. 1060. The Tunicata may be better subdivided according to the anatomical characters, and the mode of existence, of the respective species, than by arranging them according to their solitary or united condition. On this principle two Orders will be formed ; one including the isolated and aggregated Ascidite; and the other, the Salpce. The prominent differences in these two Orders are these. In the Ascidice the two orifices usually approach one another more or less closely (Figs. 701, 702). The body is either fixed immediately to some solid mass, or attached to it by a peduncle. And the branchial apparatus consists of a sac or bag, bearing a branchial network of small square meshes, occupying the greater part of the cavity of the mantle, and hav- ing the entrance to the oesophagus at its lower part. In the Salpce (Fig. 703), on the other hand, the two orifices are placed at the opposite extremities of the body, which is generally more elongated than in the Ascidire. They seldom attach themselves to any fixed basis, but rather to floating bodies ; and many of them seek no support from other masses, but trust themselves to the waters of the ocean, in which they seem to have some power of spontaneous motion. Instead of a capacious but simple bran- chial sac, we find a long narrow tube, in which a riband-like fold of vascular membrane stretches from end to end, and serves as the special apparatus for the aeration of the blood. TUNICATA.— ASCIDI^:. 429 ORDER I.— ASCIDI^E. 1061. It is perhaps among the solitary Ascidia, forming the the family ASCIDIID^:, that the highest organisation presents itself, which occurs in this class. The two orifices are both evident on the upper part of the body ; but the branchial aper- ture is the most prominent. Within this may be observed a fringe of tentacula, which are sometimes of considerable length and minutely divided, sometimes short and simple. Their office appears to be, to guard the entrance to the respiratory sac ; and it would seem probable that substances unfit to enter it are kept out by the closure of the muscular ring, excited through the nervous apparatus by irritation of the tentacula ( ANIM. PHYSIOL. § 436) ; beyond these, no organs of sense can be detected. The solitary Ascidiae are found in all climates ; they generally fre- quent the shallow waters of the shore, so as to be occasionally left uncovered by the tide. In some localities they are so abund- ant, as to afford an important source of nutriment to Fishes ; and some species are employed as food even by Man. The power of ejecting the contents of the branchial sac is their prin- cipal means of defence. Some of the larger species are able to shoot the fluid to a height of three feet ; and thus the person who places his hand upon one of them, is very likely to receive a deluge of water in his face. We are not justified, however, in attributing this action (as some have done) to any intelligence ,on the part of the animal. It is the only movement which these simple beings can perform ; and is evidently a reflex action, which any bodily irritation, whether internal or external, will excite. Some of the Ascidi7 is continued into them. Some are so little divided at the edges, that in external form they approach the Clypeasters (§ 1102); whilst in others the disk seems almost absent, the animal being, as it were, all rays. In general organization, however, there is a pretty close correspondence throughout. — The Asterice appear to enjoy a considerable amount of loco- motive power. Their rays are very flexible, so that they can be drawn up towards the mouth, or moved from side to side towards each other, so as to give the animal the power of insi- nuating itself through narrow apertures. The rays appear to be principally moved by the general integument, which is thick and contractile. Small red points have been observed at their extremities in some species, which, from their connection with the nervous cord of each ray, and from their analogy with the eyes of other Invertebrata, are believed to be visual organs. This belief is strengthened by the observation of Professor Forbes, that the spines are disposed around them in a peculiar circular mode, so that they may be closed over these organs for their protection, or may diverge for their most extended employment. The same gentleman has remarked that these animals appear to take cognizance of objects of food placed at a little distance from them ; and that, in their movements from place to place, they seem to be aware of obstacles in their direct path, and to go out of their way to avoid them. It has been remarked also that, when all their feet are protruded, they will suddenly retract them, if any substance be brought in close proximity to them, but without touching them. 1106. Notwithstanding their possession of this amount of perceptive power, however, they do not seem to be very sus- ceptible to painful impressions. If severe mutilations be per- formed whilst the animal is in a state of activity, it does not appear conscious of them, but continues its movements as before. The suckers in the neighbourhood of the injured part are re- tracted ; but the others, even in the same ray, continue their actions, as if unaffected by the sense of injury. Of the extent to which reproduction of parts may take place after such mutila- tions, details have already been given. — The Asterice are animals 468 GENERAL CHARACTERS OF STAR-FISH. — CRINOIDEA. of great voracity. Like the Actiniae, they seem to be always gaping, as it were, for food ; and to swallow whatever falls in their way. The mouth is extremely dilatable, so that it can admit large shell-fish and Crustacea, as well as small fishes, and fragments of larger bodies which may be cast upon the shore. Like the Sea- Anemone, they usually disgorge the indigestible parts by the same orifice ; and they seem also possessed of the power of partially everting their stomachs, or turning them inside- out, so that the lining membrane projects through the mouth. Indeed it is in this condition that they frequently lie in wait for their prey ; the protruded portion being wrapped round the ob- ject, and then drawn in. It seems to be by some means of this kind that the Asterias are able to destroy and digest Oysters and Mussels, without drawing their bodies from the shell. 1107. In the OphiurcevrQ find a more distinct central disk than in the Asteriae ; and to this the viscera are confined. It is furnished with arms, which are sometimes simple or undivided from one extremity to the other, and of a rounded tapering form, like a serpent's tail, as in the genus Ophiura; whilst in other genera, as the Euryale, they ramify minutely, dividing regularly into branches, which .again subdivide, so as to form a most com- plex series of appendages. These arms are all composed of jointed plates, like those of the Asteria; and they are possessed of spines or scales. The Ophiurce are much more active in their habits than are the Asteriae. Their rays seem very flexible ; and by the contraction of their envelope they may be moved in all directions. Thus they are able to swim and to walk with con- siderable facility ; as well as to exercise considerable power in obtaining their prey. ORDER III.— CRINO'lDEA. 1 108. This interesting Order of Echinoderms, which was form- erly much more abundantly represented, receives its name from the lily -like form which several of its members present (Fig. 709). All of them, instead of moving freely where they will, CRINOIDEA.— COMATULA. 469 are attached, during a portion or the whole of their lives, by a peduncle, or footstalk, to some solid body. They all seem to possess two orifices to the digestive cavity. Of this Order the Cotnatula is the most abundant example ; and as its organisa- tion is better understood than that of any other genus, our no- tion of the character of the group is principally derived from it. In general form, the Comatula does not depart widely from some of the animals just described. The star4ike aspect is still regularly preserved; and the mouth is in the centre of what must yet be regarded as the under surface of the body. The viscera are contained in the central disk, which is composed of numerous polygonal plates. The arms arising from this disk are five in number; but . they speedily subdivide, each usually separating into four. These are composed of a number of calca- reous pieces, solid and nearly cylindrical, which are inclosed in a living flesh of greater thickness than the integuments of the Asterice. Thus we have seen the rays, which in the Asteriae contained the principal part of the animal, first deprived of the prolongation of the stomach, and then losing their cavity alto- gether, so as to become mere locomotive appendages to the central disk. To the skeleton of the arms, we find that jointed lateral appendages, of a similar structure, are attached ; and these also are clothed with the fleshy integument which secretes them. Between these lateral appendages is a slight furrow, occupied by papillae, which are furnished with vibratile cilia ; and it appears to be principally by the action of these cilia, that food is brought towards the mouth. Although the digestive cavity has two orifices, it is not constructed upon the plan of .that of the Echinida. There is no separate alimentary canal ; but only a stomach like that of the Asterice, with a short tubular prolonga- tion, of which the orifice projects between the mouth "and the side of the disk. (This projecting orifice, which is very evident in the Encrinites, has been commonly mistaken for the mouth, which is much less apparent.) At the surface of the disc opposite to the mouth, the Comatula is furnished with a number of short, jointed arms, which serve it in place of legs for adhering to 470 CRINOIDEA ;— COMATULA ; PENTACRINUS. rocks and other solid submarine bodies. The mouth is then di- rected upwards, and the long, branched arms are waved about in various directions in search of food, presenting a very elegant appearance. 1109. In its young state the Comatula is fixed to submarine objects, being attached with the mouth upwards to the upper extremity of a long flexible stalk composed of calcareous cylin- ders. In this form it closely resembles a great group of Echinoderms, which were formerly excessively abundant, as their remains sometimes constitute nearly the whole mass of thick strata of rock, and which were attached by a similar flexible calcareous stem during their whole existence. The young Comatula^ in the attached state, was indeed formerly re- garded as a member of this group, and described as such under the name of Pentacrinus europceus, but it is now known that at a certain period of growth the disc and arms quit the stem, and pass the remaining term of their existence in a state of freedom. The only living representatives of the Encrinidce, or true Sea-lilies, are inhabitants of the West Indian seas, where a few specimens of two or three species have been found at great depths. One of these, the Pentacrinus caput Medusce, is of considerable size, and it is to its discovery that we are indebted for the greater part of our knowledge of the anatomical structure of this re- markable group of animals, most of whose representatives have so long since passed away. In this creature the disk and arms are formed like those of the Comatula ; the latter are thickly set with jointed lateral appendages of considerable length. The stem is more than a foot long, and composed of a large number of pieces similar to those of the arms. From this stem there arise, at regular intervals, several verticils, or .whorls, of second- ary arms ; which do not subdivide, and are destitute of lateral appendages. All these parts are covered with a fleshy integu- ment, by which they are produced, and to which they owe their power of movement. This integument seems to dip down be- tween each joint, and to form the connecting medium between the different pieces. As the base of the stem of the recent species CRINOIDEA ; — PENTACRINUS. 471 has never been obtained, the mode by which the Pentacrinus attaches itself to solid bodies has never been clearly made out ; but there is reason to believe, from the circumstances under which fossil remains are sometimes met with, that the animals of this genus are not permanently adherent to solid masses, but have the power of occasionally detaching themselves. 1 1 10. In some of the fossil species, the subdivision and rami- fication of the arms is carried to a much greater extent than in any of the recent forms of this tribe. The number of pieces in the skeleton thus becomes very large. In the Pentacrinus Briar eus, it has been calculated that at least 100,000 exist, exclusively of the joints of the lateral appendages, which are probably more than 50,000 additional. As each joint was fur- nished with at least two bundles of muscular fibre, one for its contraction, the other for its extension, we have 300,000 such in the body of a single Pentacrinus — an amount of muscular appa- ratus far exceeding any that has been elsewhere observed in the Animal Creation. But it will be remarked that these parts are but repetitions of one another in structure, and that consequently their variety of actions must be very small ; and, accordingly, we find that the movements of this complex piece of mechanism are far less capable of being combined and adapted to a specific purpose, than those of a prehensile structure of higher organi- sation— the hand of Man— with its twenty-seven bones and thirty-nine muscles. A repetition of similar parts always implies a low degree of organisation, as it indicates a very small amount of variety in the functions to be performed ; and the approach towards a higher character is marked by the modification of some of these for particular purposes — a specialisation, or setting apart, for some object of a more im- portant nature than those general functions to which they all contribute. But the simple actions, which alone can be per- formed by the arms of the Pentacrinus, are all that it needs for the grasp of its food. . 1111. The general structure of the Encrinus, of which no recent species exist, bears a close affinity with that of the 472 ENCRINITES.— HOLOTHURIDA. Pentacrinus. The body and jointed stem exhibit rather a rounded than a pentagonal form ; the latter is often destitute of second- ary arms ; and the principal branches do not ramify with the same minuteness as those of many Pentacrini, but rather resemble in their distribution those of the Comatula. The stalk is attached by a sort of spreading root, like that of many Corals ; and we must therefore believe this tribe of Crinoidea to have been en- tirely fixed. — Besides the Encrinus and Pen- tacrinus, there are many other extinct genera of Crinoidea, which present a very beautiful series of forms, all referable to the same general type ; but on these our limits forbid us to dwell. — In the recent species of Crinoidea, one or two of the arms may occasionally be found, of much smaller size than the rest, and apparently in process of replacing others which have been accidentally lost. Among the fossil Crinoidea, such instances are by no means rare. 7og _ENCRINT78 ORDER IV.— HOLOTHURIDA. 1112. This Order may be regarded as leading from the Echinida, which may be considered as the types of the Class, towards the Articulated series. In some respects it may be con- sidered to present a higher grade of organisation than we else- where meet with among the Echinodermata ; but this does not entitle it to rank as the typical order of the class ; since its more elevated character is only obtained by its approach towards a very different type of organisation. This Order, which consists of the Holothuria and its allies, is known by the comparatively small amount of calcareous matter contained in the skin ; this never forms an armour of plates and spines, but is met with only in the shape of scattered grains. The skin is soft, and very HOLOTHUHIDA ; — nOLOTHURIA. 4/3 distensible and contractile ; so that the size and form of the body are capable of great variation. The tubular feet, however, still usually exist. They are sometimes arranged in distinct rows} stretching from one end of the body to the other ; and sometimes scattered irregularly over the surface. The general form of the body varies considerably in the different species. In some it is of a nearly globular shape, as in the Echinus ; not flattened at the poles, however, but prolonged at these points. In others it is still more lengthened, and presents slight transverse markings. And in the most aberrant species, the body exhibits an almost worm-like form ; being greatly prolonged, and contracted at intervals into distinct articulations. Nevertheless, in all these, FIG. 710.— PENTACTA. the radiated type is evident in the conformation of the parts around the mouth. This is situated at the anterior extremity of the body, and is surrounded by appendages more or less ramified and fringed; so that, on looking down upon these parts only, we might almost suppose them to belong to one of the Stellerida. 1113. Although the body is not furnished with any complete calcareous skeleton, we occasionally find a circle of plates around the mouth. These afford attachment to the muscles, which stretch along the entire surface of the body, and which are con- cerned in its alterations of form. The mouth does not lead to a distinct stomach ; but it is the commencement of a long aliment- 474 HOLOTHTTRIA; SIPUNCULUS. ary tube, of nearly uniform diameter throughout ; which, after many convolutions, terminates at or near the opposite extremity of the body. — The Holothuria has the power of drawing inwards its tentacula, and of closing its mouth around them ; so that no appearance of them can be seen. It is probably by a movement of this kind that it swallows its food, which seems to consist of almost any kind of organised matter that falls in the way o ' the animal ; for the intestine is generally found distended with sand, in which may be detected the remains of corals, sea-weeds, and other marine substances. In the Holothuria the sucking feet are distributed irregularly over the surface of the body ; but in the Pentacta (Fig. 710) they are arranged in five longitudinal rows. In the Psolus, again, they are confined to a flat disc, which thus forms a foot analogous to that of the Gasteropod Mollusks, which these animals somewhat resemble in form ; and in Synapta they are entirely wanting. — There are some interest- ing points in the internal organisation of this group, which tend to show its relationship to the Articulata; and their analogy to that group is further shown in their power of comparatively active locomotion. By the flexibility of their integument, and the muscular fibres with which it is furnished, they are able to swim and crawl with facility. Some of them frequent deep waters ; whilst others are found among rocks and floating sea- weeds, at no great distance from the shore. 1114. Near the Holothuria we are probably to place the Sipunculus and its allies; although the worm-like aspect of their bodies, and the entire ab- sence of either prickles or tubular feet from the skin, would lead us to suppose them entirely different PIG. 711-8IFUXCDWS. in Character. In fact they consti- tute an extremely aberrant group — just such as' the philosophic Naturalist might expect to find between classes formed upon types so different as the Radiated and Articulated. The mouth is not surrounded by radiating arms, as in the Holothurice^ but it is armed, in many species, with a set of teeth arranged in a pentagonal form, like those of SIPUNCULUS.— GEOGRAPHICAL DISTRIBUTION. 475 the Echinus. In some, however, this is replaced by a sort of proboscis, which may be protruded or retracted like that of many Annelida (§ 906). So great a resemblance, in fact, do such animals bear to certain species which we find in this Class, that they have been arranged by many Naturalists amongst the Annelida, and their true place may still be regarded as doubtful. Nothing can be imagined that is wanting to complete the con- nection between these two classes, which is established by means of this group. The Sipunculi are seldom found but on sandy shores. They excavate holes in the sand, in which they conceal themselves, occasionally protruding their heads from the orifice. They are much sought after by fishermen, who use them, like the common lob-worm (Arenicola piscatorum\ as baits for their hooks. Some of them attach stony particles to their skin, by a glutinous exudation, so as to cover it with a hard crust, resem- bling that formed by some Annelida (§ 911), others take up their abode in the abandoned shell of Mollusca, whilst one or two species are able to excavate a habitation for themselves in the solid substance of rocks and corals. 1115. In regard to the Geographical distribution of the Echinodermata, it may be stated generally, that all the forms of this Class are represented in nearly every portion of the globe. As in other classes, however, so in this, it would appear that the largest species are found in tropical regions ; but Echini, Asterice, and Holothuria, occur in plenty on our own coasts. Star-fish occasionally abound so much on the shores of France, as to be used for a profitable manure. We have no certain knowledge as to the animals which find in the Echinodermata their regular food. Of the Stellerida, Man makes no other use than that just stated; and of none of the Echinida does he eat any other part than the roe (§ 1099). This is also said to fur- nish a large portion of the food of the Salmon during its sojourn in the sea. Of the Holothurice, one species is collected and eaten by the poor inhabitants of the Neapolitan coast ; but there is another which constitutes an important article, not only of consumption, but of regular traffic. Captain Flinders (1803) fell in with a fleet of Malay proas, near the Gulf of Carpentaria, on 476 HOLOTHURIA; TREPANG. — GEOLOGICAL DISTRIBUTION. the north coast of New Holland ; and was informed that sixty proas, carrying one thousand men, had left Macassar two months before on an expedition to that coast, the object of which was the collection of trepangs for the Chinese market. The trepang, beche de mer, or sea-cucumber, is no other than a Holothuria, which is extremely abundant on that coast ; in shallow water the animal may be taken up by the hand ; in deeper water it is obtained either by diving or spearing. In order to preserve the edible portion of it, the body is split down one side, boiled, and pressed with a weight of stones, then dried in the sun and stowed away in bags. About a thousand of them make a picol, which is equivalent to 1331bs. ; and 100 picols are a cargo for a proa. It would seem that European traders have now become alive to the value of this traffic ; for there are regular establish- ments in different parts of the Dangerous Archipelago, for those who go beche-de-mer-ing, as the employment is commonly termed. After exhausting the supplies furnished by one island, they pass on to another, and usually complete their cargo within a few weeks. The quantity annually sent to China from Macassar, which is the principal market of the trepang, is usually about 7000 picols, or 416 tons ; the price varying from 8 dollars a picol to 115, according to the quality. There is also a consider- able export of trepang from Manilla to Canton. The Sipuncu- lus, also, is used as an article of food in China and Japan. 1116. The Geological position of the different groups of Echinodermata presents us with many points of great interest. No remains of any of them can be traced in the very oldest fossiliferous rocks ; but, judging by the abundance of the skele- tons of Crino'idea in the limestones of the Transition series, the animals of that group must have been among the most numer- ous of the larger inhabitants of the ocean, at the time these strata were deposited. So abundant are they, indeed, that they may be almost said to constitute those thick and extensive beds of Transition limestone, which, from the wheel-like form of the separate joints of the Encrinite stems, are termed Entrochal Marble. " The substance of this marble," says Dr. Buckland, "is often almost as entirely made up of the petrified bones of GEOLOGICAL DISTRIBUTION OF ECHINODERMATA. 477 Encrinites, as a corn-rick is composed of straws. Man applies it to construct his palace, and adorn his sepulchre ; but there are few who know, and fewer still who duly appreciate, the sur- prising fact, that much of this marble is composed of the skele- tons of millions of organised beings, once endowed with life and susceptible of enjoyment, which, after performing the part that was for a while assigned to them in living nature, have con- tributed their remains towards the composition of the mountain masses of the earth." Fragments of Encrinites are also dis- persed irregularly throughout all the deposits of the Transition period, intermixed with the remains of other contemporary marine animals. No other species of Echinodermata, however, as yet present themselves; and it is interesting to remark, that the Crino'idea which so abound in the Transition epoch, be- longed, with one exception, to the Encrinus and other round- stemmed genera, and were therefore more unlike the existing forms of that family, than were those which we find at a later period. All these Crino'idea, which continue to abound in the Mountain Limestone and other of the more ancient secondary rocks, become extinct when we arrive at the Lias ; and are then replaced by the Pentacrinus. The stems of Encrinites compose extensive beds in the Carboniferous, as in the Transition series ; and these are often found in the neighbourhood of those of a dis- tinctly Coralline nature, so that the animals probably grew on the banks of such reefs as are now being elevated in the South- ern Ocean, and which, if properly examined, might be found to support their living analogues. The joints of the Encrinite- stems often fall asunder when the connecting rock is not firm enough to hold them, — the animal membrane which united them in the living state having long since decayed away. Their flat round form, and central perforation, have occasioned them to re- ceive the name of Entrochi, or wheel-stones. They were form- erly strung as beads for rosaries ; and in the northern parts of Britain they still retain the appellation of St. Cuthbert's beads. " On a rock by Lindisfarn Saint Cuthbert sits, and toils to frame The sea-born beads that bear his name." VOL. II. L L 478 GEOLOGICAL DISTRIBUTION OF ECHINODERMATA. 1117. The Pentacrinus first began to abound at the com- mencement of the Lias ; and its remains present themselves in great numbers in that formation, and in the Oolite which suc- ceeds it. From that period they diminish, and we gradually lose sight of this interesting group, — the few existing species serving, as it were, but to indicate the structure of those, which formerly occupied so important a rank among the inhabitants of the ocean. — As the Crinoidea disappeared, the true Stellerida and Echinida took their place ; and remains of these are met with in almost all marine strata, down to the present time, — being particularly abundant in the Chalk and Oolite. CHAPTER XXIV. OF THE CLASS OF POLYPIFERA. 1118. No doubt can now exist of the Animal character of the beings composing this class ; although the Plant-like form which many of them present, deceived the Naturalists of former days, as it does the uninformed observer at the present time, into the belief of their Vegetable nature. In the works of the older Botanists, the zoophytes, whether hard and stony, or flexible and horny, were arranged and described with Sea-weeds and Mosses, without any misgivings as to the propriety of doing so. So far was this theory carried, that the Sea- Anemone was described as a veritable flower; and Count Marsigli, who de- tected the existence of analogous beings in coral and madrepore, spoke of them as the blossoms of these stony plants. It is now about a century since the doctrine of their Animal character, now universally admitted, was received with any degree of favour by the learned. 1119. It is only of late, however, that the Polypes have been carefully investigated and well understood. A large proportion of those compound structures, which are known as Coral, Madrepore, &c., come under the inspection of Naturalists only in their dry state, stripped of all that characterises the living animal. Hence their classification has, until recently, been founded solely upon the characters presented by these structures. Some of them are massive and stony ; others of more delicate conformation, and of horny consistence. Some of them serve as a central axis or stem, which is clothed with the living flesh ; others form a tube, which, sheaths the softer tissues, and this variety is presented by Polypes of very similar structure. Moreover there are some Polypes, such as the Actinia, or Sea- 430 POLYPIFERA. Anemone (Fig. 712), which do not form associations, and which deposit no hard skeleton, but which are closely allied in general structure to those that do. In the classification founded only upon the characters of the compound masses, therefore, the naked Polypes (as they were termed) were associated in a separate Order. By this method, — as by any which depends upon a single set of characters, and is therefore artificial, — beings the most dissimilar were associated together ; and those which were really allied in the structure of the individuals were separ- ated, because there was a dissimilarity in the form of the com- pound masses. 1120. The recent researches of Naturalists have also shown that many of the creatures formerly regarded as Polypes, and be- longing to an Order in which the lowest type of organisation was displayed (the Order of the Hydroida), are in reality only stages in the development of free-swimming Radiated animals, belong- ing to the class of Acalephas of Cuvier and subsequent writers ; and as it is equally unnatural to separate the young animal from its parent, or to place it in a distinct class from other animals closely resembling it in organisation, although not known to pro- duce free Acalephs, it has been usual of late to arrange the Hydroid Polypes in one class with the Jelly-fish and their allies, to which, as already stated (§ 1089), the name of Hydrozoa has been given. The class of Polypes therefore is to be regarded as including only those species which, whether simple or com- pound, possess a stomachal sac separated by a certain space from the general integument of the animal, and in which the texture of all the soft parts of the body is firmer and less gelatinous, and the whole organisation higher than in the Hydroid Polypes. These true Polypes are divisible into two Orders, distinguished by characters derived both from the animals themselves, and in the case of the compound species from the structure of the polypi - dom. The HELIANTHOIDA have the mouth surrounded by a con- siderable number of tubular tentacles, and when furnished with a polypidom, this is always of a stony nature, and the individual Polypes are imbedded in cells excavated in its substance ; the ASTEROIDA possess only eight flat, fringed tentacles ; the ani- ACTINIA OR SEA-ANEMONE. 481 mals are always compound, and the polypidom almost invariably consists of a stony or horny axis supporting a fleshy rind, in which the individual Polypes are enclosed. ORDER L— HELIANTHOIDA 1 121. Of this Order of Polypes the Actinia, so abundant on our shores, may be taken as the types, not only on account of the ease with which they may be examined, from their being amongst the commonest and hardiest of the inhabitants of the marine Aquaria now so much in fashion, but also because they exhibit in themselves the characters of a Helianthoid Polype in full per- fection, unmasked by any social peculiarities, at the same time that their usually large size renders the investigation of their structure comparatively easy. 1122. An Actinia of the ordinary form constitutes a short fleshy cylinder, the walls of which present a very firm texture. At its lower extremity this cylinder is as it were abruptly cut off, forming a flat muscular disc by which the creature adheres firmly to rocks ; the upper extremity is closed by a membrane of lar greater delicacy than the leathery skin of the cylinder itself, and forms a second disc, in the centre of which is the opening of the mouth, surrounded by a great number of tubular tentacles? arranged in several rows. When the Actinia closes its mouth, folds in its tentacula, and draws together the upper part of its body, it presents an almost hemispherical form — the flat side being attached to the rock, and the mouth being just visible at its summit ; but when the animal expands itself, the body ac- quires the more or less cyclindrical form above alluded to, the oral disc becomes nearly as wide as the base, and the fringes of tentacula display their brilliant colours to the light of day. The arrangement and appearance of these so much correspond \vith that of the petals of double flowers, still more with that of the florets of the Composite tribe, that it is by no means surprising that the uninformed observer should almost always regard this 482 ACTINIA OR SEA-ANEMONE, being as a member of the Vegetable Kingdom. The movements it exhibits are not, when superficially considered, very different from those which take place in certain Plants ; and there is nothing ridiculous, therefore, in the appellation given to it by Hughes, who, in his Natural History of Barbadoes (a work pub- lished before the distinctions between the Animal and Vegetable Kingdoms were properly understood), denominates it a sensitive plant having animal properties. 1123. The Actinice are found on the shores of every sea. As in other tribes, each species has its peculiar haunt. In general, we find them attached to rocks, which are alternately left dry and submerged by the tide. Sometimes, however, the portions which are constantly under water are selected as their habita- tion ; and they may be observed suspending themselves from the vaults of submarine reefs, or covering the sides of rocks as with a tapestry of flowers. Brilliant as are the colours exhibited by the species common on our own shores, when these are illumined by the direct rays of the sun, they are far surpassed by the glowing hues of the tropical Actinije ; and the relative abund- ance of the two is nearly the same. Many voyagers have spoken with enthusiasm of the gorgeous spectacle presented by groups of these animals ; and Le Sueur describes himself as with difficulty withdrawing from the contemplation of it, to collect specimens for examination. 1124. The Actinice which attach themselves to rocks, some- times adhere so firmly, that they cannot be removed without the laceration of their base. This fleshy disk adapts itself perfectly to the inequalities of the surface ; and even sends down little prolongations into any pits or fissures that may exist in it. There is an interesting species inhabiting the British seas, the Adamsia palliata, which attaches itself to dead shells, forming from its base a kind of horny expansion, that partly extends over their aperture. It has been remarked by Dr. Coldstream, that in all the specimens which came under his notice, a Hermit-Crab had taken up its abode in the shell. It would seem, therefore, as if the addition made by the Actinia rendered the shell pecu- liarly suitable for the habitation of this tenant. Some species of ACTINIA OR SEA-ANEMONE. 483 Actinias confine themselves to the smooth sands, on the surface of which they spread out their tentacula, and beneath which they withdraw when danger threatens. Although the body has, in general, no further covering than the leathery envelope already mentioned, there are a few species which, by means of a glutin- ous exudation from the body, form a kind of case by attaching together bits of shell, grains of sand, and other small substances. This casing would seem to have for its purpose the concealment of the animal, as much as its direct protection. Individuals of the same species, inhabiting deep water, as if aware that they do not require such a mode of concealment, form no extraneous covering, but leave the surface clean ; and this then acquires more vivid and varied tints, whilst the glandular warts by which the glutinous secretion is formed, become smaller, or disappear. One curious worm-like form (the Edwardsid), which seems to unite the Actiniae with the Holothurise (§ 1112), constructs a membranous tube for its habitation, and strengthens this with fragments of shells and gravel. It lives buried in the sand, as does also another remarkable allied form described by Mr. Gosse under the name of Peachia, which differs from all other Polypes in its possession of a posterior orifice. 1125. The stomach in the Actinia is furnished with walls of its own, and suspended (as it were) in the middle of the body, FIG. 712. — A, SEA-ANEMONE seen from above. B, SECTION OP SEA-ANEMONE ; a, cavity of stomach ; b, surrounding chambers. leaving a considerable space between its exterior surface and the general envelope. This cavity is divided by vertical partitions, which pass in a radiating direction from one membrane to the 484 ACTINIA OR SEA-ANEMONE. other, so as to form a considerable number of chambers arranged round the central digestive sac. There is not any regular com- munication between the chambers and the stomach ; although it would seem that an opening must be occasionally formed, as young Polypes are often sent forth by the mouth (§ 1 131). The partitions all have openings, however, by which the chambers communicate with each other ; and there is also a free entrance from them into the tubes of the hollow tentacula, which are formed of a membrane like the envelope of the body, and are provided with an orifice at their extremity, which the animal has the power of closing. 1126. The muscular structure of the substance of the Acti- nice is very distinct in the larger species, and confers upon the animal considerable power of prehension. Dr. Grant mentions that he has caused the common Actinia crassicornis to lift a basin of sea-water, weighing more than six pounds, by making it swallow the perforated shell of a Purpura, through the aper- ture of which a cord had been passed. By this cord the basin was lifted, without the Actinia quitting its hold — either of the shell in its contracted stomach, or of the basin to which its foot was attached. It is not surprising, therefore, that these Polypes should be able to master not only shell-fish and other animals that have little means of active resistance, but even crabs, prawns, and other Crustacea of considerable size. These indeed seem to constitute its ordinary food. The luckless individual which walks over one of these stomachs, gaping for its prey, is imme- diately secured by its tentacula, and in spite of its struggles is drawn into the mouth, which seems capable of distention to an almost unlimited degree. Sometimes the tail of a shrimp, or some other hard projecting appendage, will occasion a little trouble, and may be seen in active movement outside the mouth, when the mass of the body has been swallowed ; but this is soon restrained by the tentacula, which entwine themselves round it, and gradually convey it into the stomach. These tentacula possess a remarkably tenacious power, which is attributed to the presence of a multitude of organs known as thread-cells or Jili- ferous capsules imbedded in their substance. ACTINIA OR SEA-ANEMONE. 485 1127. These singular organs, which appear to be common to all the animals forming the section called by Leuckart Cizlen- terata (the Polypifera and Hydrozoa), consist of minute capsules or sacs, in the interior of which a slender, wire-like filament may be seen coiled up in a spiral form. On pressure, this delicate thread is suddenly emitted from its containing capsule to a great length, and it is by the agency of a number of these, simultane- ously shot forth from the tentacles, that the latter are enabled to adhere to their prey, whilst from the rapidity with which small animals are destroyed by the grasp of these creatures, and the stinging sensation experienced even by the human skin on com- ing in contact with some of them, it seem probable that some poisonous fluid may accompany the thread. It appears that the thread, or wire, as Mr. Gosse calls it, is not simply protruded from its containing capsule ; in fact, it is attached to the outer extremity of the latter, so that, delicate as it is, it must be thrown out by a process of eversion, exactly as the finger of a glove may be turned inside out. The structure of the threads in the Actinics, as well as in many other forms of the Ccelen- terata, is wonderfully complex ; for their basal part is covered with numerous minute plates, laid over one another like the scales of an artichoke ; and from a portion of this scaly part of the thread, numerous delicate hairs often spring at right angles, so as to give it the appearance of a microscopic bottle-brush. The quantity of these minute capsules is ofiten so enormous that the tentacles would seem to be composed of little else ; and certain species of Sea- Anemones, of which Mr. Gosse has formed his genus Sagartia, have the power of eniitting from pores in the skin long filaments which consist almost entirely of these fili- ferous capsules. 1128. The digestive powers appear very considerable ; for when Mollusca or Crustacea have been swallowed, the shells are subsequently rejected by the mouth, with not only their soft contents, but even their tendinous and ligamentous portions, dis- solved away. It has been said that the Actinia sometimes swallows a shell, of which it cannot get rid in the usual manner, owing to its broad diameter being turned to the mouth; and * 436 ACTINIA OR SEA-ANEMONE- that the troublesome substance works its way out through the sides of the body, the artificial aperture soon closing, and the animal appearing to suffer but little inconvenience. In rejecting through its mouth the indigestible substances remaining within, the Actinia seems to draw up the stomach towards the orifice, so as the more completely to expel its contents. Sometimes this muscular action, which is assisted by the compression exer- cised by the general envelope, is carried so far, that the stomach is everted — completely turned inside-out — through the mouth. This fact is familiar to all, who have watched the habits of these animals on the sea-shore. 1129. The Sea- Anemone never seems to decline any article of food presented to it, on account of its bulk, but makes the most laudable attempts to swallow it, though occasionally com- pelled to relinquish its vain endeavours, and even to disgorge what it had partially swallowed. Sometimes the process of digestion is going on in the lower part of a mass which has been included in the stomach, whilst the remainder is projecting above the mouth, being gradually drawn inwards. It will hence be seen, that few animals surpass the Actinia in voracity. Never- theless it is capable of fasting for a considerable period ; or, at any rate, of subsisting upon no other nutriment, than the small quantity of animal matter that may be diffused through the sea- water, in which it is kept. It is after such a fast, that the efforts to swallow are most vigorous ; and sometimes an amusing spectacle is presented by the contest of two for the same prey. 1130. Sea-Anemonies do not seem to exercise any choice in regard to food ; but will swallow whatever is placed within the grasp of their mouth, — hot even their own kind being exempt They contract their tentacula and close the mouth, not only when mechanically irritated, but even when any change takes place in the amount of light to which they are exposed. "When fully expanded, and displaying their glowing colours to the mid- day sun, a passing cloud will cause them to fold in their flower- like summits ; and even the shadow of the hand will produce the same effect. The following interesting account of those inhabiting a rock-basin on the shore of Barbadoes, is given by ACTINIA OR SEA-ANEMONE. 487 Hughes in his Natural History of the Island. " In the middle of the basin, there is a fixed stone, or rock, which is always under water. Round its side, at different depths, seldom exceeding 18 inches, are seen at all times of the year, issuing out of little holes, certain substances that have the appearance of fine radiated flowers, of a pale yellow, or a bright straw colour, slightly tinged with green, having a circular border of thick-set petals, about the size of, and much resembling, those of a single garden marigold. I have attempted to pluck one of these from the rock, to which they are always fixed, but never could effect it : as soon as my fingers came within two or three inches of it, it would immediately contract close together its yellow border, and shrink back into the hole of the rock ; but if left undisturbed for about four minutes, it would come gradually in sight, expanding, though at first very cautiously, its seeming leaves, till at last it appeared in its former bloom. However, it would again recoil, with a surprising quickness, when I came within a little distance of it. Having tried the same experiment by attempting to touch it with my cane and a slender rod, the effect was the same." This last statement shows a high degree of sensibility to light ; since there is no reason to believe that any special organs of vision are possessed by these animals, which can enable them to see objects in their neighbourhood. They appear also to be, like some plants, very easily influenced by atmospheric changes ; and this, even when kept for some time within-doors. The Abbe Dicquemare, who watched their indications for many years, considered them a most valuable marine barometer ; fine weather being indicated by their expansion, bad weather by their closure, and very boisterous weather by their extreme contraction. 1131. These movements are not the only ones, however, un- connected with the prehension of food, exhibited by these inter- esting animals. They are observed frequently to distend them- selves with water, so as to attain many times their usual size, — the membranes of the body becoming proportionally thinner. This water is not taken in by the mouth alone ; indeed it is doubtful if any enters there under these circumstances ; at any rate, the chief part is introduced through the orifices at the 488 SEA-ANEMONE; ITS REPRODUCTIVE POWERS. extremity of the tentacura, and the distension exists iu the radiating chambers and arms rather than in the stomach. The water is afterwards expelled in jets through the same orifices with considerable force ; so as to rise to the height of a foot or more. There is reason to believe that this process is chiefly one of respiration. The whole interior of the chambers, into which the water is received, is covered with vibratile cilia ; and it has been observed that, if Actiniae are kept in a limited quantity of water, from which the air is soon exhausted, the distension of the body is enormously increased, so that its appearance almost resembles that of an inflated bladder. Sometimes this distending process appears to be performed for the purpose of facilitating locomotion. The animal is then almost of the same specific gravity with water ; and, if it withdraws its foot from its attachment, it is carried away by the least agitation of the water, and may thus go in search of a new abode without exertion of its own. When it is cast upon a surface adapted to its wants, it forms a new attachment ; and there remains, until deficiency of food or some other cause again excites it to removal. It is said that, when thus supported by the water, it can use its tentacula for assisting in its movements ; and can even walk upon these, turning its mouth downwards. It can, however, glide along the surface of a rock, by the alternate contraction and expansion of the fleshy foot in one particular direction, — in just the same manner that the Snail, or other Gasteropod Mol- lusca, perform their movements. 1132. The power enjoyed by the Actinia of reproducing parts of which it has been deprived, is almost equal to that pos- sessed by the Hydra (§ 1173). Our knowledge of it is principally due to the experiments of Dicquemare. He found, that if the tentacula be cut off, they are soon replaced. If the body be divided transversely, — so that the upper portion possesses a mouth and tentacula but no base, and the lower one has the base and open stomach without a regular mouth or tentacula, — both parts will continue to live, the one gradually closing its under side,* and forming a new disk, the other after some * Th s is not always the case, however. In one instance, a new set of tenta- cula were sent forth, and a complete new mouth formed, at the lower orifice ; so that the animal could take food by either. SKA- ANEMONE; ITS REPRODUCTIVE POWERS. 4^9 months acquiring a complete new set of tentacula and a perfectly- formed mouth. The upper part did not seem conscious of the loss of its base; but, like Baron Munchausen's celebrated horse, took food presented to it, even though it passed out almost immediately by the orifice newly-created below. If the body be divided vertically, each half becomes in time a perfect animal, capable of performing all its functions; and it would appear that such a division occasionally takes place sponta- neously. The following very curious instance of the power, which the structure of this animal has, of adapting itself to circumstances, is related by Dr. Johnston. " I had once brought me a specimen of Actinia gemmacea, that might have been originally two inches in diameter, and that had somehow con- trived to swallow a valve of Pecten maximus of the size of an ordinary saucer. The shell, fixed within the stomach, was so placed as to divide it completely into two halves, so that the body, stretched tensely over it, .had become thin and flattened like a pancake. All communication between the inferior portion of the stomach and the mouth was of course prevented ; yet, instead of emaciating and dying of an atrophy, the animal i.ad availed itself of what undoubtedly had been a very untoward accident, to increase its enjoyments and its chances of double fare. A new mouth, furnished with two rows of numer< us tentacula, was opened upon what had been the base, and led to the under stomach : the individual had indeed become a sort of Siamese twin, but with greater intimacy and extent in the union." — It sometimes happens that, in tearing away an Actinia from the rock, some portions of the disk are left behind ; and even these are said to be capable of developing perfect individuals. The following circumstance is mentioned by Hughes, in the account already quoted. " Many people coming to see these strange creatures, and occasioning some inconvenience to a person through whose grounds they were obliged to pass, he resolved to destroy the objects of their curiosity ; and, that he might do so effec- tually, caused all the holes out of which they appeared to be carefully bored and drilled with an iron instrument, so that we cannot suppose but their bodies must have been entirely crushed 490 REPRODUCTION OF SEA-ANEMONE. to a pulp ; nevertheless they appeared in a few weeks from the very same places." The Actiniae have not only the power of repairing injuries of this description, but seem to resist the effects of other agents in a very remarkable manner. They are not killed by being frozen in a mass of ice, but return to activity when thawed ; and they withstand the action of water heated to 140°. They may be placed with impunity in the exhausted receiver of an air-pump ; and yet their life is destroyed in a few minutes by immersion in fresh water. 1133. We do not find in the Actinias, anything exactly resem- bling the reproduction by buds, which is so remarkable in the Hydra. The spontaneous division of the body just alluded to, — which is said to take place occasionally, not into two parts onlj, but into several — constitutes an approach to it. The special t reproductive apparatus, by which distinct germs are formed, is here very highly developed ; consisting of numerous very com- plicated membranous bands enclosed within the chambers already described (§ 1125) as surrounding the stomach. The germs are said sometimes to escape by the tentacular orifices, but it seems more probable that they pass into the stomach through an orifice at its bottom, and are then cast forth by the mouth. They are sometimes extruded in the state of simple gemmules furnished with cilia, like those of other Polypes. Sometimes, however, they are retained for a longer period, and their development goes on within the body of the parent, so that when liberated they already present something of the form of the adult animal, having a mouth, stomach, and tentacula, — the latter being at first few, but gradually increasing in number. In the course of six years, an Actinia, kept by Sir J. Dalyell, produced above 276 young. If all these had been preserved, and their progeny reckoned, the amount would have been enormous. The young are frequently disgorged along with the half-digested food ; thirty-eight appearing thus, in various states of development, at a, single litter. Monstrosities are not uncommon among the young. One is mentioned by Sir J. D., which had two perfect bodies springing from a single base. When one body was gorged with food, the other continued ravenous. — The process of respir- I SEA-ANEMONE.— CAR YOPHYLLIA. 491 ation already described, appears to have an important connection with the development of the progeny ; and the introduction of water into the ovarial chambers may not improbably furnish them with supplies of food as well as of air. 1134. The Actinia have been stated to feed upon small Crustacea, Fish, &c. In their turn, they become the prey of the larger species of these tribes. They constitute by no means an unpalatable article of food, even for Man. Particular species are highly prized as delicacies in some tropical countries ; and others are commonly employed by the inhabitants of northern shores. Along our own coasts, there is a remarkable neglect of these and of many other marine productions, to which, if not constantly employed, recourse might be advantageously had in times of scarcity. They seem to have been a favourite dish at the Abbe Dicquemare's table. " Being boiled some time in sea- water," he tells us, " they acquire a firm and palatable consist- ence, and may then be eaten with any kind of sauce. They are of an inviting appearance, of a light shivering texture, and of a soft white and reddish hue. Their smell is not unlike that of a warm crab or lobster." Mr. Gosse also describes their qualities as articles of food in high terms. 1135. The Actinia are by no means the only Polypes be- longing to this Order. Several other genera exist, of which some are, like it, unpossessed of any calcareous deposit, whilst others form a hard skeleton more or less complete. Between these, however, there are links of close connection ; for some among the first have a portion of the base and of the lower part of the cylindrical body hardened into a kind of horny cell, within which the animal can retract the upper portion that re- mains soft. In those species which construct a stony basis, the calcareous matter is deposited in the same situation. Such a deposit is formed by the Caryophyllea, a solitary Polype much resembling the Sea-Anemone, which is to be met with on the southern shores of England ; and thus a stony cell is formed, in the bottom of which are to be seen a number of thin vertical plates or lamellce, formed in the partitions between the ovarial 492 STONY CORALS; — CARYOPHYLLEA, DENDROPHYLLIA. chambers, and, like them, radiating from the centre towards the circumference of the cell. These radiating lamellae are, in fact, characteristic of all the Coral structures formed by the group of Helianthoid Polypes ; being present, more or less evidently, in every one known to be the work of these animals. The cells are not by any means constantly circular ; but still the laminated plates project inwards from their circumference, so as to occupy a corresponding position. The Madrepores and their allies have thence been designated lamelliform corals ; a term which is very expressive of their character, and has the advantage of relating to the structure of the animals which produce them. 1136. Some species of Caryophyllea build up their cells in a cylindrical form, to a considerable height (Fig. 713). As the upper edge is extended by the gra- dual consolidation of the soft structure, which is the continuation of it, the lower part is strengthened by new de- posits, which are added to the bottom of the cell ; so that a stony column is thus formed, which may almost be described as solid through nearly its whole extent. It is not uncommon to meet with several of these, clustered in one mass ; and FIG. 713.-CARYOPHYLLEA. tnus we cjm understand the production of those arborescent (tree-like) forms, to which the name Dendrophyllia has been given. In these, the stem sends out branches, instead of remaining simply columnar ; and these branches again subdivide ; in all instances, however, the cells terminate the branches, which increase in length by the progressive consolidation of their bases, just as in the solitary species. The whole structure is covered with a gela- tinous flesh of some consistence, which seems to be continuous with the outer membrane of the Polypes inhabiting the cells. This flesh appears to have the same functions with the pith of the Ser- tularian Polypes (§ 1177). It seems, in fact, to constitute the STONY CORALS; — DENDROPHYLLIA. 493 animal, of which the Polypes are only subordinate parts. It has no direct communication with their stomachs, however ; nor does it appear to connect the different Polypes very intimately together. But it is largely concerned in the deposition of the calcareous matter of the polypidom, especially in those forms of it in which the cells are connected together by a solid mass (Fig. 714), instead of being seated, as in the Dendrophyllia, upon the extremities of diverging branches. Even here it may be observed, however, that a new twig or ramification is at first produced, not by a Polype, but by a projection of the flesh, of which the centre becomes consolidated, forming a cell in which the Polype subsequently appears. The same takes place in the early development of the gemmules. Moreover, if a piece of this flesh be stripped from the surface and placed in sea-water, it will begin to form a cell, by the deposition of calcareous mat ter, upon the spot where it happens to rest ; and this cell is soon tenanted by a Polype like an Actinia. Many other arborescent forms of lamelliform corals might be enumerated, which are of great beauty to the common observer, and highly interesting to the Naturalist on account of their affinity with the extinct species so abundant in limestone rocks.* Amongst these are the true Madrepores, in which the whole surface of the stem and branches is covered with minute cells. In all these, as in the plant-like Sertularidce (§ 1177), the living flesh is withdrawn from the lower part, in proportion to the extent of growth above ; and, if attached to a limestone rock, the root can scarcely be distin- guished from the basis on which it has been implanted. 1137. We now pass to another series of forms presented by the lilhophyte corals ; — those in which the Polype-cells, instead of being placed on the ends or sides of branches, are distributed over a continued surface, sometimes in close apposition with each other, sometimes widely separated, but united by a solid calcareous mass which fills up the interspaces. Of the first of these kinds, the common Astrcea affords an excellent example. We might * It may be desirable to remark that the Red Coral and its allies do not be- long to this group, being destitute of laminated cells. They will be descrited among the Alcyonian Polypes (§ 1159). VOL. II. M M 494 STONY CORALS; — FUNGIA. imagine it composed of a number of Fungice packed closely together. Here the same gradual consolidation of the lower part of the cells takes place, as in the Caryophyllea; so that the mass acquires considerable thickness. The cells of these Polypes do not always, however, preserve their regular rounded form ; being sometimes oval, and in many instances forming a long fur- row, as in the Meandrina. Each of the furrows, however, is occupied by several Polypes arranged side by side; and their point of junction is usually indicated, either by a slight transverse partition in the furrow, or by a change in the direction of the laminae arising from its sides. In the Meandrina cerebriformis (brain-stone coral), the whole mass, whether young or old, is nearly hemispherical. It is at first small, but extends in all directions by a process of growth and consolidation analogous to that already described ; so that, whilst its surface is always covered with a living flesh, and studded with vast numbers of polypes, the interior is a mass of solid limestone, the particles of which remain cemented together by the animal matter in which they were at first deposited. On breaking this hemispherical mass, the ridges which bound the furrows may be traced inwards through its substance, even to the central nucleus from which they commenced ; the deposit in the interstices of these being of a softer character, and possibly more of the nature of an exudation from the under surface of the flesh. These Meandrince sometimes attain a considerable size. Ehrenberg noticed single masses, in the Red Sea, from six to nine feet in diameter. Their rate of growth, however, appears to be slow. 1138. It is principally by the animals of this group, that FIG. 714. — MASS OF ASTRJEA VIRIDIS ; a, a, expanded Polypes .- b, b, Polypes with- drawn into their cells ; c, stony mass uncovered 'oy flesh. RATE OP GROWTH OF CORAL. 49 J the formation of coral reefs and islands is effected. Manv errors have prevailed upon this subject, both as to the rapidity of their extension, and the depth from which they are built up to the surface of the ocean. It has been commonly stated thar, many channels and harbours in the Red Sea have been closed up, within the memory of man, by the rapid increase of coral limestone. But Ehrenberg, who carefully examined these localities, attributes the obstruction rather, in some instances, to the quantities of coral sand which have been washed into the harbours, and in others to the accumulation of ballast (generally composed of pieces of coral rock) thrown out from vessels. In Captain Beechey's Expedition to the Pacific, no positive in- formation could be obtained of any channel having been filled up within a given period ; and he states, as an indisputable fact, that several reefs had remained, for more than half a century, at about the same depth from the surface. On the other hand, there is evidence of the occasionally rapid growth of these structures. In the Museum <5f the Bristol Institution is a mass of Agaricia, weighing 2 Ibs. 9 oz., surrounding a species of Oyster, whose age cannot be more than two years. Pieces of coral, detached from a reef, and thrown into some other situation, soon become fixed by the deposition of new stony matter, if the animal flesh have not been too much destroyed ; and in this manner a sort of arti- ficial reef may be formed in any spot desired, provided the depth of water be suitable. The natives of the Polynesian Islands have long employed this method for building their piers, wharfs, fish-preserves, &c. Mr. Stutchbury mentions that he saw, at the Island of Taapoto, in about seven fathoms water, the anchor of a large ship, wrecked there not more than fifty years previously ; this was completely incrusted by coral, though it preserved its original form. One of the most interesting proofs of the occa- sionally rapid growth of Coral, is afforded by the alteration in form which is seen in two kinds of shells that inhabit the reef* — the Vermetus and Magilus (§ 995). 1139. There can be no doubt that, whether the growth of Coral takes place as rapidly as some maintain, or as slowly as it is believed to do by others, it is among the. most important at' 496 FORMATION OP CORAL ISLANDS. tl»e progressive changes, which have been altering the surface of the Globe since it has been tenanted by Man. To it is due the existence of a large proportion of the Islands of the Polynesian Archipelago, as well as many of those in the Indian Ocean ; and the extent of these islands is far less than that of the reefs, which are not yet raised above the level of the sea, — some presenting themselves at a distance from any upraised land, others fringing the shores of continents and islands, composed of other formations. It is not correct, however, to affirm (as has been frequently done) that these islands and reefs have been upreared by the Coral- polypes from the depths of the ocean. It is now satisfactorily ascertained that no known species can build from a greater depth than twenty fathoms ; and a large proportion seem to prefer a depth of from twenty to thirty feet. As very deep water is found in the immediate neighbourhood of many of these reefs, the question arises, upon what basis they are constructed ; and to solve this, it is necessary to look at the forms which these massive structures present. 1140. A large proportion of the Coral Islands of the Poly- nesian Archipelago are shaped like a crescent, sometimes like a complete ring ; and these islands never rise many feet above the surface of the ocean. The highest part is always on the windward side,* against which the waves are almost constantly dashing. Within the crescent or ring is a basin, termed a lagoon ; and this usually communicates with the open sea, by a channel, sometimes of considerable width, on the leeward side of the island. Occasionally this channel is completely filled up by the growth of the Coral ; and the lake, thus inclosed, only commu- nicates with the sea by filtration through the Coral rock. The Coral-polypes never build above low- water mark ; and they are not, therefore, immediately concerned in the elevation of the surface from beneath the waves. This is principally accomplished by the action of the sea itself. Large masses are often detached, by the violence of the waves, from the lower part of the structure ; and * The prevalence of easterly winds in the tropical regions, causes this name to be given to the eastern side of islands situated there ; the western shore beiag known as the leeward. FORMATION OF CORAL ISLANDS. 497 these (sometimes measuring six feet by four) are washed up on the windward side of the reef. Shells, coral-sand, and various other debris, accumulate upon it in like manner, until it is at last changed into an island, upon which there is a calcareous soil capable of supporting various -kinds of vegetation. When these have once established themselves, the elevation of the surface continues with greater rapidity — successive layers of vegetable mould being deposited by the rapid and luxuriant vegetation of these tropical islands, which are soon tenanted by various forms of animals, and at some subsequent period afford a habitation to Man. It is not usually, however, until after the windward coast has attained considerable elevation, that the leeward side is perfectly closed in. Two causes may be assigned for this. There seems to be a natural instinct on the part of the animals, which impels them to build with greater rapidity on the most exposed side ; and the leeward side is therefore the part last completed. Moreover the closure of tfiis passage is impeded by the current almost constantly passing out of it, which is caused by the dashing of the waves over the windward side into the lagoon ; and until this ceases, there will always be a free exit in the opposite direction. After the wall has been sufficiently upraised, however, the lagoon is often completely enclosed. In the centre of this lagoon, deep water is often found, and no living animals can be seen upon its bottom ; but the shelving edges of the shallower portion are clothed with luxuriant growths of the more delicate species of coral, and its waters abound in marine animals of all descriptions. 1141. These lagoon-islands vary in diameter from one to fifty miles ; the breadth of the elevated ring which encloses the lagoon, is from 400 or 500 yards to about a mile, though seldom above half a mile ; and its height above the water is not often more than four or five feet in any part. The annular (ring like) cha- racter of these islands naturally suggests the idea, that they may have been built upon the edges of submarine volcanoes, or upon circular elevated ridges, forming basins, resembling those whiofi abound in the parts of the globe at present upraised, and whicn may reasonably be supposed to exist in those still submrr^ert. 498 FORMATION OF CORAL ISLANDS AND REEFS. In support of this doctrine, it has been stated that fragments of volcanic rocks have been found in the water of a lagoon. That there is nothing in the essential nature of coral structures which impels them to assume this form, is evident from the fact mentioned by Ehrenberg, that in the Red Sea the islands are oblong or square without lagoons ; as well as from the variety which we meet with even in the Polynesian Archipelago. In fact, they always appear to correspond with the form of the base on which they are erected ; and the evidence that some lagoon islands (at least) are founded upon the tops of submarine volcanoes, or upon the edges of large basins, seems therefore satisfactory. But it is difficult to conceive that there should exist beneath the ocean so large a number of summits, all so nearly approaching its surface, as these must do in order to form a basis for coral islands, — not to mention the other ridges on whiuh the reefs are built, which will next be noticed. This difficulty appears to be solved by the very ingenious hypothesis put forth by Mr. Dar- win, which will be presently explained. 1142. .Almost all the shelving shores of tropical seas are fringed more or less closely by ridjes of Coral. These are not built immediately upon the edge of the land, but at some little distance from it. If the wall of coral were upraised close in-shore, the fresh water draining down from the land, and entering the basin thus formed, would render it unfit for the habitation of the Polypes. They are, therefore, endowed with a power of choosing a situation more advantageous to their growth ; and we accordingly find these skirting reefs upraising themselves at some distance from the shore, but not so far off as to have a base of greater depth, than is suitable to the constitution of the Polypes. Very often such reefs run from point to point of a bay, so as completely to enclose it.* But beyond these skirting reefs are * In the little island of Cariacou (one of the chain of Grenadines, between Grenada and St. Vincent) the whole coast is a succession of such bays, and each of these is shut in by such a reef ; a narrow passage into one of them being the only means of access, when the Author visited it a few years since. From a hill in the centre of the island, nearly every part of the coast can be seen ; and the white 1'nes of surf, connecting the d 3 k rocky points, present a very striking appearance. The Society Islands are generally skirted by similar reefs, which are generally 400 FORMATION OF CORAL REEFS. 499 sometimes other ridges, often at a considerable distance from the shore, but still preserving a direction parallel to it. These are termed barrier reefs; and the most remarkable of them is the one, which stretches along the north-eastern coast of New Hol- land. The total length of this is above 1000 miles ; along 350 miles there is no break or passage whatever ; and for 700 miles northwards towards New Guinea, there are no intervals exceed- ing thirty miles in length. When we endeavour to account for such a structure upon the commonly received opinions alone, we are met by the same difficulty as that, which opposes itself to the supposition of a rocky base to all the coral islands, at a depth of less than 120 feet. There is no mountain range, extending to anything like the length of this reef, of which the summits are so nearly equal in height ; — still less any one presenting a continu- ous ridge, such as would be required for the base of the uninter- rupted portion of the reef. We have, therefore, no right to suppose that such a ridge should arise from the depths of the ocean ; and yet without it, our knowledge of the habits of the Coral Polypes does not enable us to account for the remarkable structure under consideration. 1 143. This difficulty, however, appears to be satisfactorily solved by Mr. Darwin's hypothesis. He has adduced several reasons for the belief, that the bottom of the whole Pacific Ocean is changing its level, in some parts slowly subsiding, whilst in others it is undergoing gradual elevation. Now if we imagine the whole of New Holland to have been at a former time con- siderably more elevated than at present, its area would of course have been greater, and it might have extended to the line of the present reef. This reef might have then been formed as a skirting reef in the usual manner ; stretching at the distance of a few hundred yards along the whole coast in shallow water. If a slow subsidence then took place, the coral would be kept up to the surface of the water, by the labours of the Polypes, in an almost unbroken ridge ; whilst the water would gradually gain or 500 yards off-shore, with a deep channel, into which ships can enter by nume* rous passages. — These passages are generally opposite the mouths of fresh-water rivulets. 500 EFFECTS OF SLOW SUBSIDENCE. upon the land, and increase the distance of its shore from the reef. In this manner the skirtiny reef, upraised from a depth of ten or fifteen fathoms, and at a distance of five hundred yards from the shore, may be gradually converted into a barrier reef, with water one hundred and fifty feet deep on each side of it, and the shore one hundred miles off. Let us imagine the gradual sub- sidence to continue, until the whole of New Holland should be submerged, with the exception of its loftiest hills. These would then remain as rocky islands rising out of the ocean ; but the barrier reef would continue in its present aspect, since it would be still maintained on a level with the surface, by the labours of its innumerable builders, although the depth of its base would be constantly increasing. If a rapid subsidence were to take place, however, the summit would be submerged to a depth inconsistent with the vitality of the Polypes ; and all increase must then cease. 1144. It is evident that this hypothesis will be equally appli- cable to the case of the lagoon-islands. If the area over which they occur were formerly more elevated, some of its volcanic peaks and circular ridges might have lifted themselves high above the ocean ; others would have been nearer its level ; and others might have been just submerged. Upon the latter, the formation of coral would have begun; and circular reefs would have been built up to the surface. If a slow subsidence then took place, these reefs would still retain their surface-level by addition, whilst a new set of hills would be submerged, and would serve as bases for new coral islets. In this manner all the summits, however different their original elevation, would be rendered of an uniform height ; each, as it was sub- merged, becoming the basis of a coral growth, which keeps pace with the^ progressive lowering of the whole mass ; — and so on until all are thus submerged, and no land but coral islets remains above the surface. 1145. This very ingenious hypothesis corresponds well with the fact that, over certain large areas of the Pacific, we find lagoon islands and barrier reefs abundant, whilst skirting reefs are scarcely ever met with. Moreover, actual proof of a slow EFFECTS OF ELEVATING FORCES. 501 subsidence is not wanting. Tims in the Keeling or Cocos Islands, situated in Lat. 11" 50' S., and Long. 96° 51' E., the old cocoa- nut trees surrounding the lagoon, in which the water is as tranquil as in the most sheltered lake, are undermined and falling. The foundation posts of a store-house, which, according to the inhabitants, had stood seven years before just above high- water mark, were, at the time of Mr. Darwin's visit, washed by the tide. The islands are occasionally shaken by earthquakes. Such changes are by no means unfrequent in many parts of the Pacific ; and, if the accounts of the natives are to be relied on, many instances of the submergence of whole islands have occurred, within the period of recent tradition. 1146. The evidence in regard to the areas of elevation is still more satisfactory. It is by no means uncommon to find beds of recent Coral, at a considerable height above the sea level. Some- times whole coral islets are thus upraised. Among these, Elizabeth or Henderson's Island, examined by Captain Beechey, is one of the most remarkable. This is about five miles in length and one in breadth. It has a nearly flat surface ; and on all sides, except the north, is bounded by perpendicular cliffs about fifty feet high, composed entirely of dead coral. In some parts, the height of the surface was nearly eighty feet above the water level. The face of the cliffs presented a smooth surface, and was destitute of any ridges or other indication of the action of the sea at different levels ; so that it may be reasonably inferred, that it was upraised by one convulsion. At a distance of a few hundred yards of this island, no bottom could be gained with 200 fathoms of line. — The most remarkable instance of this kind on record is the one observed by Mr. S. Stutchbury in the island of Tahiti. This island is composed of volcanic rocks ; and there is in it a lofty mountain ridge with two summits, of which the lower one is evidently the crater of a volcano, perhaps not very long extinct. The principal peak rises to the height of about 10,000 feet ; and near its summit is a distinct and regular stratum of coral-limestone, which cannot be distinguished from that, which is being at present formed in enormous quantity around the shores of the island. As there is no other deposit of 502 GENERAL EFFECTS OF CORAL-GROWTHS. coral, either on the sides of this mountain, or on the summit of the volcanic crater, it is a reasonable inference that the island must have been upraised, to the whole amount of the elevation of the ancient ridge of coral above the reefs at present in course of formation, at one movement. — In the bands of the Pacific Ocean, regarded by Mr. Darwin as areas of elevation, no lagoon islands or barrier reefs are met with ; but the shores are fringed by skirting reefs ; and active volcanic changes are not of infre- quent occurrence. 1147. The following remarks by Mr. Darwin form a very appropriate conclusion to this part of our subject : — " It is not that the ocean spares the rotk of coral ; the great fragments scattered over the reef, and accumulated on the beach, whence the tall cocoa-nut springs, plainly bespeak the unrelenting power of its waves. Nor are there any periods of repose granted. The long swell, caused by the gentle but steady action of the trade- wind always blowing in one direction over a wide area, causes breakers, which even exceed in violence those of our temperate regions, and which never cease to rage. It is impossible to behold these waves, without feeling a conviction that an island, though built of the hardest rock, let it be porphyry, granite, or quartz, would ultimately yield and be demolished by such irre- sistible forces. Yet these low insignificant coral islets stand and are victorious ; for here another power, as antagonist to the former, takes part in the contest. The organic forces separate the atoms of carbonate of lime one by one from the foaming breakers, and rear them up into a symmetrical structure. Let the hurricane tear up its thousand huge fragments ; yet what will thus tell against the accumulated labour of myriads of archi- tects at work day and night, month after month. Thus do we see the soft and gelatinous body of a polypus, through the agency of the vital laws, conquering the great mechanical power of the waves of an ocean, which neither the art of man nor the inani- mate works of nature could successfully resist."* 1148. Much discussion has taken place in regard to the sources, from which the Coral-polypes obtain the enormous quan- * Darwin's Journal, p. 548. SOURCES OP LIME IN CORAL. 503 tity of lime deposited by them ; and this question affects not only those of the present epoch, but those of former ages, to whoss labours, in conjunction with those of the testaceous Mollusks, the greater part of the Calcareous strata of the secondary and sub- sequent periods are immediately or remotely due. Some have gone so far as to imagine, that the lime is produced by some organic pro- cess in the animals themselves. No positive evidence of such a production can, however, be obtained from any source ; and the hypothesis is quite unnecessary in the present instance. We have reason to bolieve that lime existed in large quantities on the surface of the earth, before any organised beings were placed upon it ; and there is also ground for supposing, that a larger quantity of carbonic acid existed in a free state at that epoch, than at the present time. It is not improbable, therefore, that the waters of the ocean contained a much larger quantity of lime than they now do — this ingredient being held in solution by the free carbonic acid ; and the enormous beds of calcareous rock, separated by the action of Coral-polypes, are therefore easily accounted for. Moreover, in volcanic countries at the present time, springs charged with carbonate of lime thus held in solution are very abundant ; and it is not unfair to suppose that, — as the part of the globe in which the coral-formations increase most rapidly (the Pacific Ocean), is also one of the chief areas of submarine volcanic action, — such springs may occur with similar frequency, and may greatly assist in the growth of these masses' In illustration of this doctrine, it is remarked by Mr. Lyell that, in lakes which have no unusual supply of carbonate of lime, there is no accumulation of shell-marl — the thin shells of one generation of Mollusks decomposing, so that their elements supply the requisite materials to succeeding races. But, if springs or streams charged with carbonate of lime enter such a lake, the shells accumulate and form marl. There are many plants and animals, in whose economy lime appears to be an important agent; and the quantity introduced bears a strict relation (within a certain limit) to that with which they are supplied. ORDER II.— ASTEROIDA. 1149. In many of the Polypes of this Order, the polypidom, or solid framework, so closely resembles Sponge, that, in the dry state, the former can only be distinguished by the regular dis- position of cells upon its surface ; and, in the immature con- dition, the resemblance is still more close, — the young branches of the polypidom, on which the polypes have not yet appeared, presenting all the characters of sponge. There is a great ap.- parent diversity in the character of the members of this Order. Whilst one family approaches the Sponges so closely, that it might almost be regarded as formed of Sponges provided with polype-mouths, another has a dense horny, or even calcareous, arborescent stem ; whilst in another, the soft parts of the body are entirely inclosed in a firm tubular sheath. But, however dif- ferent in the character of their aggregated masses, they all bear a general resemblance, as to the structure of the individual Po- lypes ; and to these we shall first, therefore, direct our attention. 1150. None of the Alcyonian Polypes live so entirely isolated as the Actinia. On comparing the external appearance of one of them with that of a Sea- Anemone, we perceive that, whilst the mouth is surrounded by tentacula in the same way, there is a marked difference in the form and number of these prolonga- tions. Instead of numerous short cylindrical tubes like those of most of the Actinice, we find six or eight broad leaf-like expan- sions, disposed with great regularity around the mouth, so as very much to resemble a Star-fish (Asterias). Hence the term Aster oida has been proposed as a designation for the group ; and it represents sufficiently well its chief external character. These tentacula are unprovided with cilia; but a number of little projections may be seen along their margins, which pro- bably increase their prehensile power. The mouth leads into a stomach, which resembles that of the Actinia, in being suspend- ed in the midst of the general cavity of the body, by partitions STRUCTURE OF ALCYONIAN POLYPES. 50.") radiating from its walls. Instead of being closed at its lower extremity, however, it opens into the canals which ramify through the fleshy mass, and which thus connect all the Polypes into one system. This opening is surrounded by a circular muscle, or sphincter, by the action of which it may be expanded or entirely closed. The chambers which surround the stomach correspond in number with the tentacula ; and these are hollow, opening below into the chambers (as in the Actinia), whilst they have a small orifice at their ex-4 tremity. The chambers are con-" tinuous at their lower part with ria.-i5.-ALCYONiAxpoi.YrK. the ramifying canals just mentioned ; and the membranous folds which support the stomach do not cease at its lower extremity, but are prolonged downwards as plaits of the lining of these canals, until they gradually disappear. 1151. The ova or germs are developed in the substance of the membranous folds, or from the lining of the canal. They grow like seeds in a seed-vessel ; at first appearing as little pro- tuberances from the plane surface ; then acquiring a distinct globular form, and remaining attached by a little stalk; and finally, being liberated by the separation of this pedicle. They then make their way outwards, by passing into the stomach through its lower aperture ; and finally escape by the mouth. Like the gemmules of other Polypes, they consist in this state of a membranous bag including fluid ; and they are covered with cilia, by the action of which they move freely through the water for some time before fixing themselves, though not with the same rapidity as the ova of some other Polypes. They are usually coloured with great vividness ; and, during their motions, they often contract themselves and alter their form. 1152. Very little is known of the general habits of these Polypes ; but they probably differ but little from those of the groups already described. We may pass on, therefore, to con- 506 GENERAL STRUCTURE OF ALCYONIAN POLYPES. sider, the chief subdivisions of this Order, which includes many very interesting and well-known forms. These subdivisions are principally founded upon the nature of the polypidom ; and it is desirable, before proceeding to describe them, that the relation of the parts of which the animals are composed should be clearly understood. Delicate as is the membrane of the Polypes them- selves, it may be distinguished, like that of the Sertularians (§ 1177), into two layers. — Of these, the outer one is continuous with the general envelope of the whole mass ; whilst the inner one lines the canals which ramify through it. But instead of these two membranes being in contact, as are the horny sheath and the lining of the tubes in the Sertularians, a thick mass of flesh is interposed between them ; and it is usually in this flesh, and not in either of the membranes, that the hard deposit takes place, which gives firmness and support to the general structure. 1153. The family we shall first consider, includes those species which, have a spongy polypidom, — of which the Alcyo- nium is a characteristic example. Here the general form and aspect closely re- semble those of the Sponges ; but, in the living state, it will be evident that the projecting orifices are tenanted by Polypes ; and, even in the dry skeleton, it may ge- nerally be observed that the openings of the large canals are not simple, like those of the vents of Sponges, but present some in- dications of the radiating partitions already mentioned. Between the large canals, into which the Polype-stomachs open, there is a net-work of minute tubular ramifications, which connect them PIG. "16.— ALCYONIUM ; A, portion enlarged, showing the Polypes. ALCYONIUM. 507 very intimately. In the interstices of these ramifications, which are occupied by the gelatinous flesh of the animal, spicula of cal- careous matter are deposited either in a circular or granular form ; these, as in Sponges, give a general support to the whole mass, though not consolidated in any one point. The general vitality of the polypidom, however, would seem to be greater than that of Sponge. If a single Polype be irritated, it with- draws itself within its tube ; and the edges of the cell, which were at first prominent, become nearly flat. IfVthe irritation be more severe, several of the neighbouring Polypes also withdraw themselves ; and if it be sufficiently prolonged, a collapse and contraction of the whole polypidom is evident. The analogy is very striking between this phenomenon, and that exhibited by the Sensitive Plant, in which the effects of the irritation are manifested at a greater or less distance, according to its intensity (VEGET. PHYSIOL. § 422). If, instead of the Polypes being irritated, a portion of the general surface be touched, a curious series of changes will take place. After some little time the part touched becomes opaque, more dense, and depressed; and, if the stroke be severe, this contraction will extend through the whole mass, and the Polypes also will shrink. This is pecu- liarly evident if the vessel containing the animal be smartly struck ; since the shock will then be simultaneously felt through the whole structure. Even the complete division of the poly- pidom with a sharp knife, does not produce so evident an effect as a slight shock, of which the effect is thus diffused. On the other hand, when at rest and undisturbed, the Polypes protrude their bodies, unfold their beautifully-formed tentacula, and take in a large amount of water. This is transmitted through the whole interior of the polypidom by its anastomosing canals, and the mass becomes distended to twice or thrice its original size; and from being firm and opaque, it becomes soft and pellucid. 1154. The general integument of this spongy mass has a firm leathery texture, and sometimes contains a distinct calcareous deposit; as does also that continuation of it, which forms the I • 508 ALCYONIUM. external coating of the Polypes themselves. From the integu- ment the buds are produced, which originate in the spongy structure itself, and are, in fact, prolongations of it. These are traversed by canals, that branch off from those of the parent mass ; and resemble pieces of Sponge in every important par- ticular. It is not until the Polypes are developed at the ter- minations of these canals, that the real character of the mass can be positively stated. This is another example, in addition to the number we have already seen, of the progressive development of the higher forms of organised beings ; and of the correspond- ence between its several phases, and the forms which remain permanent in the lower parts of the scale. 1155. The form and dimensions of the various species of Alcyonia differ as much, as do those of the Sponges, to which they bear so great an external resemblance. The Alcyonium digita- tum creeps along the surface of loose stones and shells, forming a thin fleshy crust, which rises up in irregular lobes or projections. This small species is so abundant on some parts of our own coasts, that scarcely a stone or shell can be dredged up from deep water, which does not serve as a support to one or more specimens of it. The particular form it presents, varies according to the nature of the surface on which it grows. Sometimes it spreads out into finger-like projections ; and hence has received from the fishermen the name of Dead-man 's-hand. Other species attach themselves to rocks, and grow like Sponges, hanging down from the upper surface of submarine hollows in the face of overhang- ing cliffs. Others of still firmer texture stand erect beneath the shallow waters of the shore. Of this land one of the most remarkable species, probably the largest Alcyonium at present existing, is the A. poculum, or Neptune's cup, which was dis- covered by Sir Stamford Raffles upon the Coral reefs that sur- round the Island of Sumatra. Many specimens, brought from the neighbourhood of Singapore, now exist in the Museums of this country ; and among these, some have attained the dimen- sions of nearly three feet in height, and eighteen inches in diameter. Their affinity with the Sponges is drawn yet closer, ALCYONIUM. — PENNATULA. 509 by the siliceous character of the crystalline deposits, to which they owe their firmness ; and, by some Naturalists, this species has actually been referred to the class Porifera. 1156. In one family of this Order, the polypidom is unat- tached. Of this irroup, the Pennatula, or Sea-pen, is a charac- teristic example. It consists of an axis which is stony for a considerable part of its length, but is flexible at its two extrem- ities. This is clothed with a flesh, which extends along the sides into pen-like prolongations, arranged like the barbs of a feather ; and one edge of each of these is fringed by Polypes. The skin contains a large amount of calcareous spicula, and is often deeply coloured ; being, in the British species Pennatula phosphorea, purplish-red along the stalk, and orange at its ex- tremities. It is not often that the Pennatula? rise to the surface. They are usually brought up by fishing lines from considerable FIG. 717.— FENNATULA. depths, where they live fixed in the mud by the lower extremity, which is always destitute of pinnules and Polypes. It was for- merly supposed that the Sea-pens floated freely in the water, and that they were even capable of swimming by the action of their fin-like lateral processes ; but there is no doubt that this notion was erroneous, and that they are really rooted in the mud by the basal prolongation of their stem. Some of the Pennatulee are very brilliantly phosphorescent ; and the appearance of the larger species, when displaying their luminosity in the dark ocean, is very striking. The disengagement of light is, how- •ever, by no means constant ; but, as in all other instances of phosphorescence, depends upon the condition of the animal. VOL. II. N N 510 PENNATULA. — ASTEROID POLYPES. When it is irritated or alarmed, a vivid emission takes place ; but this soon dies away. When frequently struck by the waves, it is possible that they may continue the display with little inter- ruption ; but observation proves that, when preserved in calm water, they do not voluntarily disengage light, although they readily show it if disturbed. The accompanying figure repre- FIG. 718. — VERKTILLUM. sents a genus of Alcyonian Polypes nearly allied to the Penna- 1 tula. The Virgularice and Pavonarue, which also belong to this t group, are of an exceedingly elongated and slender form, some of; them measuring three or four feet in length. They are com- 1 monly known as " Sea-rushes." 1157. The next group of Asteroid Polypes includes manyj well-known species, — such as the Red Coral, the Gorgonit orj Sea-fan, the Antipathes or Black Coral. In all of them thej structure of the Polypes is nearly the same ; and the differences of the polypidom chiefly relate to the portion, in which the solidification of the structure has taken place to the greatest extent. It will be recollected that, in the true Alcyonia, the calcareous or silicious spicula are deposited, as in the Sponges, through the whole mass ; and that with the exception of the fibrous bands which interlace between the canals, no one portion is harder than another. Now in the group at present under consideration, a solidification takes place in the centre or axis of the polypidom, and often in the integument also. Almost all the species included in it have an arborescent form ; and so much does the flexible axis of many kinds resemble the stem of a plant, that, even so late as the year 1825, the celebrated Blumenbach GORGONIA, OR SEA-FAN. 511 writes—" The stems appear to be really vegetables (the woody nature of which in the strong main stems cannot be mistaken) merely incrusted with corals." 1158. Among the Gorgonice, or Sea-Fans, there are some species which very closely resemble the Alcyonia, in the uniform distribution of the firm texture through their whole substance. In others, however, a firm horny skeleton is found, which is commonly known as the Sea-fan ; and, in the living state, the flesh which clothes this is covered by a dense integument, con- taining an abundant deposition of calcareous particles. If the flesh be allowed to dry upon the stem, the integument remains as a friable crust, which may easily be peeled or rubbed off, disclosing the horny stem within. No mark of the habitation of the Polypes is ever found upon the internal axis; but the remains of the cells may often be observed in the integument, when dried over it. The dry form in which the skeleton of the Gorgonia is commonly known, does not give a correct idea of its real character ; since, in the living state, there is by no means a complete isolation between the hard axis and the soft living flesh, but the one passes gradually into the other. On cutting across the stem, it is observed that it is formed by con- centric layers, like those of a dicotyledonous tree ; and it is pro- bable that these are formed by the successive consolidation of the flesh in contact with its surface. Beyond this general analogy, however, no resemblance can be made out ; since nothing like the intricate arrangement of dissimilar parts in a woody stem, can be found in these simply-organised but beautifully- formed structures. Whilst the axis of the Gorgonia is usually brown or black, its crust often exhibits colours of great bril- liancy, especially in the living state ; in some species it is of a deep red, in others of a bright yellow, and in others of a crim- son hue. 1 159. The structure of the Antipathes is by no means unlike that of the Gorgonia. The axis is still more firm, presenting when dry a smooth polished surface, which, joined to its dark colour, has caused it to receive the designation of Black Coral The calcareous deposition in the integument, also, is still more 512 ANTIPATHES. OR BLACK CORAL.— BED COKAL. abundant; so that the crust, when dry, is sometimes even 'thicker than the stem, The solidifying matter having thus entirely left the flesh, we find it extremely soft ; — so soft, indeed, that when brought up from the depths of the sea, this substance runs off almost entirely, leaving the integument adhering to the axis. — In the Corallium rubrum, or Red Coral, the solidification of the axis has proceeded still further ; for it contains not only horny animal matter, but a large quantity of calcareous particles, so closely deposited in every part, as to give great solidity to the stem, and to enable it to receive a fine polish when cut into fragments. This is a valuable article of commerce, and is prin- cipally obtained from the Mediterranean, where it is brought up from considerable depths. No vestige of polype-cells can be detected upon the surface of the axis. These are confined to the flesh and its integument, which are both very soft; the latter does not contain enough calcareous mat- ter to make it percepti- ble as a crust when dried upon the axis. The density of the Red Coral renders it very brittle ; and, did it not grow in a somewhat stunted form, it would be liable to in- jury from the violent motion of the water in which it grows. — There is a very interesting species of this group, which connects in a re- markable manner the stony Corallium with the horny Antipathes. This is the Isis Hippu- ris, in which the stem is composed of both these substances alternately, so as to £ive it FIG. 719. —RED CORAL. ASTEROIDA.— ISIS HIPPURIS ; TUBIPORA MUSICA. 513 a jointed appearance. It is formed by the deposition of calca- reous matter at intervals along the horny stem ; and in this man- ner it is endowed with a considerable degree of flexibility. If the axis be submitted to the action of an acid, the calcareous deposit is removed ; and its structure appears uniform through- out. Although its aspect is jointed, therefore, no real articula- tions exist ; the flexible substance, of which the intervals are alone composed, being really continued through the whole. 1160. The last group of the Asteroid Polypes differs from those we have hitherto considered, in several important respects. In the Tubiporidce, each Polype is inclosed in a distinct cylin- drical tube, which is formed by a continuation of its external membrane ; and there is no communication among the individual members, nor anything like the gelatinous flesh or central axis of other Alcyonians. In some genera the tube is membranous, or somewhat horny; but in the Tubipora, the genus from which the Order takes its name, it is of firm calcareous structure. Of this genus only one species, the Tubipora musica, inhabiting the Indian Ocean, is known. It takes its name from the regular arrangement of its cylindrical tubes by each other's side ; whence it is commonly termed " Organ-pipe Coral." These tubes are of a dark and rich crimson ; whilst the Polypes themselves have a bright green colour when alive ; so that the contrast is very striking. The Polypes resemble those already described, in all the leading particulars ; except that the living membrane, which lines their interior, does not seem to extend far down the calca- reous tube ; and the ova are developed, not from its folds, but from filaments prolonged from the base of the stomach, which hang down into the cavity. The calcareous tube is formed by the solidification of the membrane, which envelopes the Polype ; and this is reflected in a funnel-shape, so as to close the mouth of the tube, within which the Polype can be entirely withdrawn. The tube is gradually prolonged by the deposition of stony mat- ter in this membrane, which is continuous with its upper edge ; and the Polype always maintains its position at its extremity. 'At intervals, however, a sort of collar is formed around each tube ; and as a number of Polypes usually grow in close proxi- 314 TUBIPORA MUSICA.— CILIOBRACH1ATA. inity with each other, and form this collar at about the same time, an almost continuous horizontal partition or floor is thus constructed, which gives great additional strength to these delicate polypidoms. This collar is produced in the following manner. The membranous continuation of the tube, instead of growing straight upwards, makes a turn outwards, as if it were flattened down all round. A double fold is thus occasioned, in which calcareous matter is deposited, and the collar is thus com- pleted. From this point the membrane is prolonged in a straight direction as before, until the new impulse arises, which causes another floor to be constructed ; and thus a succession of stories is built up. — The ova, when they issue from the parent, have little or nothing of their perfect form. They seem to fall upon a neighbouring portion of the floor, and there to begin the de- velopment of a tube, which grows up among the older ones. Thus it happens that, between every two floors, there are more tubes than in the division below ; and the whole mass assumes some- what of the form of an inverted pyramid. 1161. The most extended survey we can take of the opera- tions of the Polypifera upon the surface of the globe at the present time, will give us but a very inadequate idea of the important part which they performed, in the remoter epochs of the history of the earth. Our wonder is excited when we hear of a continuous reef of coral more than a thousand- miles in length; yet what is this to the formation of limestone strata, covering superficial areas, not only of thousands, but of tens of thousands, of square miles, to a thickness, in many instances, of 3000 feet ? Yet the Geologist of the present day has little hesi- tation in regarding these formations, as having taken their origin from the labours of these apparently insignificant and simply- organised beings. As at the present time, the greater proportion of these structures appears to have been composed of the La- melliform corals (§ 1069) ; but the remains of Alcyonian Polypes are by no means unfrequent in the limestone rocks, and are especially abundant in particular strata. 1162. There are many instances in which the Coral struc-* tures of comparatively recent origin have undergone a metamor- METAMORPHOSES OF CORAL. 515 phosis, which causes them to lose, in greater or less degree, their original aspect. Large masses, when long exposed to the airy become changed into a solid, often somewhat crystalline, rock ; in which the traces of organic structure are very indistinct, and with which the Mountain or Secondary Limestone closely cor- responds. This is observed in the Bermudas, — a group of islands, which seems to have been for the most part formed by Coral Polypes of the same species with those now existing in the seas around. — Moreover, the Coral Sand, formed by the action of the waves upon the living structure, often becomes consoli- dated into a hard stone by the filtering of water through it ; a small quantity of the carbonate of lime being probably dissolved at the surface (where the carbonic acid of the air increases the solvent power of the water), and set free again below, so as to glue together the separate particles. It is in such a mass that the human skeleton is imbedded, which was found on the shore at Guadaloupe, and is now placed in the British Museum. This stone, when minutely examined, is found to consist of a number of rounded grains, cemented, as it were, together ; and it closely resembles the rock known to the Geologist as Oolite. — Further, where shallow water exists around Coral islands, the bottom is found to be covered with a layer of white mud, which is formed by the decay of the animal matter that held together the particles of carbonate of lime in the stony corals ; and these, being thus set free in a finely-divided state, fall to the bottom in a form which, if dry, would constitute Chalk. Thus we may trace very distinctly the mode in which three principal kinds of limestone rocks may have taken their origin from Coral formations. 1163. Now, the Mountain or Carboniferous Limestone, — a rock very abundant in Britain, extending over large areas beneath the coal-fields, and sometimes exhibiting a thi«kness of nearly 3000 feet, — though in some parts evidently composed of accumulations of Shells, Encrinite stems, &c., exhibits the Coral structure very distinctly in many situations ; and these parts are so blended with the neighbouring rock, as to make it appear probable that the latter also was once in the state of coral, but 516 ANCIENT CORAL-FORMATIONS. was gradually changed by the process just described. Further, the collections of other animal remains are such, as we should expect to find on the margin of a coral reef or island existing at that epoch ; and a similar process of fossilization is taking place at this very time, on the shores of the islands now being built up, — the species of animals imbedded being, however, not the same. The great thickness of the beds of this rock may be very well ac- counted for, in the same manner as the depth of the coralline masses of recent formation (§ 1141). The Oolite had its origin in the wearing-down of the older limestone beds, with additional matter derived from the skeletons of the races of animals which existed during the period of its formation. And there can be little doubt that the C%a/£-formation owes a considerable part of its substance to the same sources ; though part was doubtless derived from the decomposition of shells, and a large proportion in some situations from the remains of animals of extreme minuteness, presently to be described (§ 1222). — There are observed, in rocks of more recent formation, appearances which still more clearly indicate that they too were originally formed by Coral-polypes. These are often found within narrow limits, as if they had been reefs or islands of small size. Thus we find a stone, called Coral- rag, in Oxfordshire ; and very distinct Coral-beds in the Crag of the eastern coast of England. It is interesting to remark, that the remains of Coral, which are found in the older lime- stones, all correspond with those at present abounding near the equator, and exhibit the Lamelliform structure (§ 1135) ; whilst they are gradually replaced, in the newer strata, by species more allied to those at present existing in temperate climates. This is one of the many facts which tend to prove that this part of the earth had at some former period a much higher temperature than at present. CHAPTER XXV. OF THE CLASS OF HYDROZOA. 1164. OF the class of Hydrozoa of modern writers, which includes the Hydroid Polypes and the Acalephae of Cuvier, it is perhaps difficult to give a general character, as the animals be- longing to it, however closely they may be related physiologi- cally, present a wonderful variety of external form. They are all, however, of a gelatinous texture, and usually of very simple organisation ; the stomach is always hollowed out, as it were, in the substance of the body ; the vascular system, when present, is of a very simple nature ; and no trace of a nervous system can be discovered in them. Like the Polypes, they capture their prey by the agency of tentacles ; and their integuments are fur- nished with a multitude of filiferous capsules, the stinging power of which in many cases is very great. 1165. The different forms presented by these animals having been already referred to (§ 1089), we may proceed at once to the consideration of the Orders into which they may be divided, al- though it must be confessed that the complex chain of relation- ship, which in this class often binds the most dissimilar creatures to each other, renders this a matter of some difficulty. Thus many of the Polypoid forms give origin to free swimming oviparous Medusae by a process of gemmation, so that these might almost be regarded in the light of reproductive organs thrown off from the parent polype in order to aid in the diffusion of the species ; but they display an organisation so far superior to that of the Polypes from which they are produced, that we can hardly help regarding the latter as larval forms ; and besides, some of the Medusae are capable of producing their like, not only by gem- mation, but even by oviparous reproduction. To render this part of our subject intelligible, therefore, it will perhaps be ad 518 HYDROZOA ; — HYDRA. visable to treat the Hydroid Polypes and Medusae provisionally as forming distinct Orders ; the number of such groups included in the class will then be four, namely — I . HYDROIDA, or the Hydroid Polypes, including all the at- tached polypiform species, whether simple or compound. II. DISCOPHORA, Medusce or Jelly-fish, in which the body con- sists of a convex disc or umbrella, from the centre of the lower surface of which depends a peduncle containing the stomach, and terminated by the mouth. III. SIPHONOPHORA, which appear to consist of free-swim- ming colonies of Polypes, analogous to the simple Hydroida. IV. CTENOPHORA, simple animals, the motions of which through the water are effected by the agency of bands of cilia which run along their surface. ORDER I.— HYDROIDA. 1 166. The Hydrate creature to which the name of Polype was first applied in modern times, is a minute animal, common in stag- nant pools of water, where num- bers are often found clustering upon aquatic plants, or other float- ing bodies. These curious little creatures possess an organisation which appears very simple, and so it has long been considered ; but recent improvements in the power of the microscope have enabled its structure to be more fully analysed, and have revealed (in this as in every other instance) details that were previously unsuspected. The Hydra viridis, or Green Polype, and the Hydra fusca, or Brown Polype, are the two best known species ; and to these our description will chiefly apply. The FIG. 72X— HYDHA. HYDRA; ITS ACTIONS. 519 oody of the Hydra consists of a simple bag, or sac, constituting the stomach of the animal, and capable of varying its form and dimensions to a very remarkable extent. In the largest species it sometimes attains the length of an inch, when stretched out in a cylindrical form ; whilst it will appear, in its contracted state, as a small globe of scarcely perceptible dimensions. At the upper end of this digestive sac is an opening, which may be regarded as the mouth of the animal ; and round this are arranged a certain number oftentacula, or long flexible arms, which diverge from each other like the spokes of a wheel. If we look at the mouth of the Hydra from above, therefore, we shall at once perceive the claim of this animal to a place among the Radiated Sub-Kingdom. The arms vary in number ; being usually from six to ten. They vary also in dimensions ; not exceeding in the for- mer species the length of the body ; whilst in the latter they often extend themselves to as much as seven or eight inches, still being able to contract themselves down to minute tubercles or knobs projecting around the mouth. The animal, in its general aspect, is thus seen to bear a close resemblance to the Cuttle-fish ;* and in the peculiar organisation of its arms for the seizure of prey, this resemblance, as we shall presently see, is extremely remarkable. In fact, this little Polype may be regarded as one of those sketches or fore-shadowings of higher forms, which we occasion- ally meet with in the lowest groups. 1 167. The arms are destitute of cilia ; and this is an import- ant character, by which all the Polypes of the Hydra-form kind may be at once distinguished from the Polyzoa (§ 1070). They are thickly set, however, with minute bristles ; besides which, a number of little wart-like processes may be observed, from whose summit sharp and firm spines are occasionally protruded, by which a very firm hold is taken of whatever substance is embraced by the animal. The mechanism by which these are pushed out of their sheath is very curious. Each spine is mounted upon the summit of a small vesicle, which is capable * It was this resemblance which caused Reaumur to give to the Hydrae the name of Polypi ; the Polypi of the ancients being the animals now included in the genus Octopus amongst the Cephalopoda. 520 HABITS OF HYDKA. of expanding and contracting within an envelope, that embraces the whole apparatus. When at rest, this vesicle lies at the bottom of the including sac, and the spine is drawn entirely within the latter ; but, when the animal lays hold of any object with one or more of its arms, the vesicle is distended by some unseen means, and protrudes the spine which is seated upon it. 1168. When in search of prey, the Hydra permits its arms to float loosely through the water. It is rather curious that so inactive a creature as this should principally depend for its food on the minute Crustacea and aquatic Worms, whose rapid move- ments would seem to place them beyond its reach. By lying in wait, however, with its arms thus disposed, the Polype soon succeeds in obtaining its supply ; for if, in their active course, any of these animals should but touch one of the tentacula, its doom is sealed ; — it is immediately seized by it ; — other arms are soon coiled round it ; — and the unfortunate victim is speedily conveyed to the mouth. It has been noticed that, if held for a little time in the arms without being swallowed, soft-bodied animals (such as worms) always die, even when released alive ; whence it has been inferred, with some plausibility, that the spines are the means of conveying into the prey some poisonous secretion, in the same manner as the poison-fang of the Serpent, or the sting of the Bee. Upon minute Crustacea and other hard- shelled animals, however, this secretion appears to have no power. Such animals are often swallowed alive, and their movements within the stomach may often be perceived for some little time ; but, their life being at last destroyed, the process of digestion goes on very rapidly. The transparency of the membrane which composes the stomach, at first permits the outline of the animal to be clearly seen. The film over it gradually becomes turbid, however, and the outline of the animal indistinct ; until, at last, its form is wholly lost. The soft parts are completely dissolved ; and the harder indigestible portions are rejected through the mouth. It would seem that Animal matter is more readily dissolved than particles of Vegetable structure. 1169. It not unfrequently happens that, in the process o swallowing, the Hydra draws in its own arms, which are coile i HABITS OF HYDRA. 521 round its prey. The digestive process never seems to affect them, however, in the slightest degree ; even though they remain thus inclosed during the whole period of the solution of the food. Trembley, the first discoverer of these Hydrde, to whose accurate description of their habits scarcely anything has been added by subsequent observations, once witnessed a very curious circumstance. " Two Polypes had seized upon the same animal ; both had partially succeeded in swallowing it ; when the largest put an end to the dispute, by swallowing its opponent, as well as the subject of contention. Trembley naturally regarded so tragical a termination of the affray as the end of the swallowed Polype's existence ; but he was mistaken ; for, after the devourer and his captive had digested the prey between them, the latter was regurgitated safe and sound, and apparently no worse for the imprisonment." It has been noticed that, when the Hydra is gorged with food, its tentacula may be touched with impunity by the animals, whose contact would at other times arouse it into active movement. This scarcely proves, however, an exer- cise of the will, to which some have referred it. We may easily understand that the distention of the whole of the tissues with fluid may be unfavourable to their contractility; and we have a parallel case in the Human being, for every one can perceive the difference in the facility of swallowing, at the commencement and termination of a full meal. It will scarcely be asserted that this variation is an effect of the will ; in fact, it is often opposed to it, being one of those beautiful adaptations, by which the welfare of the economy is provided for, but which the indulgence of the sensual appetites opposes. 1170. Amongst the many curious experiments performed on these animals by Trembley, was the following : — By means of a fine wire, he actually succeeded in turning the Hydra inside-out, as we might the finger of a glove ; and this violent disturbance did not seem to interfere with the comfort of the animal, for all its functions soon went on as before. What was previously the lining membrane of the stomach now becomes the external in- tegument, and from it the buds are produced, which will be pre- sently described ; whilst the tegumentary membrane seems to be capable of speedily doing all that is necessary, towards the di- 522 NUTRITION AND REPRODUCTION OF HYDRA. gestion of the food. The remarkable power with which these Polypes are endowed of adapting themselves to circumstances, seems to be given to them as a compensation for their low degree of organisation. While the want of cilia on their tentacula pre- vents the creation of currents for the purpose of bringing a con- stant supply of food to the mouth, and thus affords less choice to the animal, the body is so constructed as to be capable of accom- modating itself to a prey of extremely variable size j and the di- gestive secretion can act upon almost any kind of organised sub- stance, so as to convert it into alimentary materials. And, in like manner, the absence of any special means of aerating the fluids is compensated by the exposure of every part of the tissue, both by its internal and external surface, to the sur- rounding element. 1171. The reproduction of the Hydra usually takes place by means of buds developed from its external surface. At first these appear as slight protuberances from the body ; they gradually increase in size, and present somewhat of the form of the parent ; an aperture is then seen at the unattached extremity, and tenta- cula sprout around it. During the whole of this period, the interior of the young Polype communicates with the general cavity of the parent. At first its nutriment is supplied entirely by the latter ; but when the tentacula are developed, it catches prey for itself with much eagerness. It is not an unusual thing to see the young one and its parent struggling for the same worm, and gorging opposite ends of it together. There is still a communication between the stomachs of the two, as appears from the distention of either when the other is fed. As the young Polype advances towards maturity, however, this aperture con- tracts, and is at last obliterated. The stalk, by which the bud is attached, gradually becomes more slender ; and at last it is broken by any slight effort on the part of either animal, and the young one moves away. Not unfrequently, however, it has begun to produce buds from itself, before its separation from its parent ; and thus three generations may be seen united together. During warm weather, this multiplication goes on with great rapidity, if the animals are well supplied with food. From one parent, six or seven buds have been seen to sprout at one time ; a "d REPRODUCTION OF HYDRA. 523 several of these bearing another generation, as many as eighteen have been observed united in one group. Sometimes the whole process is concluded within twenty-four hours ; so that, at this rate of production, above a million would be formed in a month from a single Hydra. 1172. It is not only in this manner, however, that the Hydra propagates itself. The process just described is evidently analo- gous to the extension by buds, which is so characteristic of Plants. But there is another mode of reproduction in the Vegetable kingdom — that by seeds or spores ; and this, also, the Hydra possesses, in common with all the higher tribes of Animals. Towards autumn, some little gelatinous globules are seen to be liberated from the tissue of the Polype. These fall to the bottom of the water, and remain undeveloped until spring ; when they produce a new generation of Hydra. 1173. Perhaps the most remarkable feature in the history of the Hydra, is its capability of reproducing the whole structure from separate portions of it. Not only will the body send forth new tentacula, to replace any which have been accidentally lost or artificially removed, but the arm thus separated has the power of developing the whole body. If the body is divided trans- versely, each segment will become a new animal ; the upper one closing the aperture at its base, and the lower one speedily developing tentacula around the newly-fdrmed mouth. If divided longitudinally, each half will form a separate tube in an hour, by the folding-in of its edges, and will soon begin to ply its ten- tacula. Even if divided into several longitudinal strips, each becomes a new tube ; not as before, however, by the folding in of its edges, but by the formation of a cavity in its substance. If cut transversely into several segments, each will in time become a perfect animal, so that thirty or forty Hydrce may thus be produced by the section of one. Further, by slitting the tube at one end only, two heads or two tails may be formed — each division soon becoming perfect in itself. These may be again divided, and any amount of multiplication may thus be effected, thus realising in Nature the Hydra of ancient fable. The animal does not appear to suffer from these operations, for it is 524 SENSIBILITY AND MOVEMENTS OP HYDRA. observed that, as if excited by the injury, young Polypes sprout more abundantly from the wounds thus made, than from un- scarred parts. But even this is not all ; for two Polypes may l)e grafted together by any parts ; and not only two of the same species, but a green and a brown one may be thus united. 1174- The Polype does not seem to possess any special organs of sensation, or to have any kind of feeling but that of touch. It may be doubted, indeed, how far the greater part of its ac- tions necessarily involve true sensation ; that is, how far it is con- scious of the impressions which are made upon it, and to which its organs respond. Many of its movements present considerable analogy with those of Plants ; especially those of the Dioncea (VEGET. PHYSIOL. § 422). The Hydra generally seek the light ; and, if a number of them be placed in a glass vessel, they will cluster at the side on which it strikes. We have no reason to suppose, however, that they are conscious of its presence as light, since no rudiments of visual organs can be detected. It would rather seem that it exercises an influence on their bodies, which causes them to seek it, very much in the same manner that Plants direct themselves towards it. The locomotive powers of the Hydra are more exercised for this purpose than for the search after food. When seeking their prey, they generally fix themselves, by a kind $f sucker at the lower end of the stomach, to some solid body ; and their food is obtained by the tentacula alone. When they desire to change their place altogether, they do it in the manner of the geometrical Caterpillars (§ 768), and of some Leeches. If the foot or sucker be attached, the body is bent until the head touches the surface, along which it intends to move. It then adheres by the mouth, or by one or two of the tentacula ; and, detaching the foot, draws it up into close proximity with the head. The foot then takes a fresh attach- ment; and the head is projected forwards, fixes itself, and is followed by the foot in the same manner as before. This mode of progression is, from the minute size of the animal, necessarily slow. A march of two inches occupies several hours for its per- formance ; and seven or eight inches may be regarded as a very HYDRA.— HYDRAF011M POLYPES. 525 good day's journey even in summer. But sometimes a more expeditious mode of travelling is adopted. The head being brought down and fixed as before, the foot is made to describe a semicircle over it, and takes its new attachment at an equal distance on the other side ; the foot being then fixed, a similar movement is performed by the head ; and thus the animal ad- vances by a succession of summersets. 1175. By these and similar means, the Hydrce are enabled to move along solid surfaces, such as the bottom or sides of the vessel in which they are contained, and the leaves or stems of aquatic plants. There is another very curious position, to which it frequently has recourse. By projecting the flat surface of the foot above the water for a short time, it soon becomes dry, and in this state serves, by its repulsive action on the water around, as a kind of float, from which the animal suspends itself. In this state it can move itself, by means of its tentacula, with great facility; and it is also acted on by the wind, so that it can travel a considerable distance without effort. If, whilst thus floating, a drop of water be made to fall upon the foot so as to wet it, the hydrostatic power of the organ will be destroyed, and the animal will immediately sink to the bottom. 1176. The group of the Hydroid or Hydra-form Polypes includes, with the simple genus just described, and a few other simple but stationary forms, all those compound structures, in which a number of Polypes similar to it are associated together. In all these, the polypidom, or solid frame-work which gives support to the softer portions of the structure, is external to the living animal matter, and incloses it as in a tube. It is of a texture varying from that of membrane to that of horn ; it never contains stony matter to any amount; and it is always flexible. This horny sheath is formed by the consolidation of the living animal membrane, which originally acts as the envelope of the soft and almost fluid texture within ; and it is continuous with the external layer of that which forms the Polypea themselves. This horny tube is enlarged at certain points into sheaths or cells fcr the protection of the Polypes ; within these the individuals can retract themselves, although. VOL. n. o o 526 HYDROIDA ;— SERTULARIAN POLYPES. when in search of prey, they extend beyond it. Each single Polype resembles a Hydra in every important respect but this ; — the stomach, instead of being closed at the bottom, communi- cates freely with the interior of the stem and branches; and the membrane lining its sac may be regarded as a prolongation of that which surrounds their cavity. The pulp contained in the hollow stem, rather than the Polype itself, appears to be the essential part of the animal ; for the latter is not only formed subsequently to it in the first instance, but frequently dies, and is reproduced by it. 1177. Of all Zoophytic productions, the structures formed by the Sertularice and their allies are the most graceful in their appearance, and delicate in their conformation. They are very abundant on our own shores, seeming to pre- fer temperate to tropical cli- mates ; and they constitute a large proportion of what are commonly, but incor- rectly, denominated Coral- lines.* They have generally a plant-like aspect ; consist- ing of a stem, attached at its base (where it sometimes diverges into root-like pro- longations) to some larger mass, and sending off its branches above with extreme and most beautiful regu- larity. The cells are ar- PIO. 721.-8EETULAKIAN POLYPES. ranged upon the sides of these, like the minute leaflets of Mosses ; and it is not surprising, therefore, that by the older * The real Corallines are a much smaller group, probably of Vegetable charac- ter. In general aspect, their stems have some resemblance to those of the Sertu- HYDROIDA ;— SERTULARIAN POLYPES. 527 Naturalists, who were ignorant of the existence of the Polypes, these productions were regarded as of a vegetable nature, and • were termed Sea-Mosses. The resemblance is still more striking when the mode of propagation in the two groups is compared. 1178. Although the reproductive gemmules are in some instances produced from the Polypes themselves, as in the Hydra, a more special apparatus is usually evolved for the pur- pose. At certain periods, there are formed from particular spots upon the stem of the Sertularia and its allies, expansions of its horny structure, somewhat resembling those which encase the Polypes, but usually larger. These ovarial vesicles, which so much resemble the urns of Mosses (VEGET. PHYSIOL. § 429), are like them provided with a lid, which falls off when the con- tained gemmules are mature, so as to permit their escape ; and after their purpose is thus completed, the vesbles fall off, like the seed-capsules of all plants. The gemmules are usually clustered around a central column (analogous to the columella of Mosses) ; and when mature they swim forth by the action of the cilia with which they are provided, being detached from the central column at the same period that the lid of the vesicle falls off. The gemmules move to and fro by the vibration of their cilia, during a period which varies from a few hours to two or three days. When they have fallen* upon a site fit for their development, they attach themselves to it by a root-like fibre, and then begin the formation of the polypidom. The real nature of this gemmule has been elsewhere explained (ANIM. PHYSIOL. § 745). In some instances the embryo before quitting the ovarial vesicles acquires exactly the form of an exceedingly minute Medusa. 1179. Besides the Hydne and Sertularia3 there is a third type of Hydroid Polypes, the Tubularics. In these, which, like the Sertularian Polypes, are for the most part compound animals, the polypidom is usually of a soft and membranous texture, some- times quite rudimentary or altogether wanting ; and the Polypes larian Polypes ; and hence thjey are associated together in the minds of those ignorant of this department of Natural History. The real Corallines may be distinguished by the absence of any trace of cells upon their surface. 528 TUBULARI.E. themselves are always more or less clavate at the extremity, and -are capable of being completely retracted within their polypidom even when this is present. It is from Polypes of this group, and from some marine forms resembling the fresh-water Hydra, that true Medusae are produced by gemmation ; and we shall see hereafter that there are important differences in the latter, ac- cording to the form of the polype-nurse from which they ori- ginate. The true Tubularice, however, display some curious phenomena in their mode of reproduction. Besides the repro- duction by gemmation, which is common to them and all other compound Polypes, they have the power of producing a number of ovigerous vesicles at certain seasons, in the form of small clusters of bulbs attached to the clavate head at the bases of the tentacles. In each of these a vitelline vesicle makes its appear- ance, but the further progress of this presents a wonderful variety. Sometimes it is developed into a single embryo furnished with tentacles, upon which, according to Sir J. G. Dalyell, it i able to crawl about at the bottom of the water until it meete with a suitable spot for its permanent abode ; when it reverses its position, so as to bring the tentacles upwards, becomes at- tached by the opposite extremity, and developes itself into a Polype resembling its parent. The young embryo closely re- sembles a contracted Hydra. In other cases the vitelline vesicle becomes divided into several parts, each of which gives rise to a small ciliated embryo, analogous both in its structure and mode of production to the ordinary embryo of the Sertularian Polypes. But sometimes the vitellus becomes converted into a globular Medusiform embryo, which swims by the contractions of its body, after the rupture of the capsule containing it, and either becomes directly converted into a Polype resembling its parent, or by the division of the vitelline mass contained in it gives origin to numerous ciliated embryos of the kind above alluded to. This complicated mode of reproduction is very analogous to that which takes place in the following Order, and is peculiarly interesting as occurring in animals so closely allied to those from which many of the Medusae are produced. 1 180. Almost all the compound Hydroida are inhabitants of the TUBULARI^E. 529 ocean. Some of them seem to attach themselves indiscriminately to any solid mass; whilst others seem to have a preference for some particular kind of support. Thus, some are found only on rocks which are constantly beneath the surface ; others on those which are occasionally uncovered by the sea ; and others attach themselves to the fronds of Sea- Weeds, which are exposed by the reflux of every tide. The deserted shells of Mollusca are the favourite bases of many species ; and a few attach themselves even to these tenants of the deep whilst yet alive. The duration of these structures is various. Many of them do not exist above a year, especially such as are parasitic upon Algae ; but others, particularly those which attach themselves to rocks, probably attain a much greater age. It would seem, however, that the age of the Polypes cannot be measured by that of their cells. In some instances all the Polypes disappear during the winter, dying off like the leaves of a tree ; and they are all renewed with the light and warmth of spring, whilst at the same time fresh branches are produced. In other species, a constant death and regeneration of the Polypes seem to take place. 1181. One of the most curious phenomena exhibited by the Polypes of this group, is the circulation which may be seen to take place in the stem and branches, and which seems to con- nect the different individuals together. This circulation much resembles that which has been described in the compound Asci- dians (§ 1065), and is, like it, reversed in its direction at intervals ; but only a single current can be seen at a time ; and it is not maintained by any visible movement of the walls of the cavities or tubes in which it takes place. The flow is sometimes very rapid ; it then slackens, and at last stops ; and recommences, sometimes immediately, sometimes after an interval, in the oppo- site direction. Five ebbs and flows have been observed to occupy about fifteen minutes. ORDER II.— DISCOPHORA. 1182. In the animals of the Order Discophora, as indicated in their name, the most striking character consists in the umbrella- 530 DISCOPHGRA. like disc, convex above and concave below, which forms the upper part of the animal. It is by the continual contraction of this disc, as they float in a somewhat oblique position, that the animals are enabled to swim slowly through the water, and it is from this circumstance that their old name of Pulmograde Acalephce was given to them. The texture of these curious creatures is perfectly gelatinous, and usually transparent or translu- cent, whence the names of "Jelly-fish" and "Sea- blubber," which are com- monly applied to them. Their substance consists of a tissue somewhat resembling cartilage (ANIM. PHYSIOL. § 45); but • contains so little solid matter, that a Me- dusa, weighing several pounds when alive, is FIG. 722.-PELAGIA. reduced nearly to as many grains when dried. The fluid, which differs little, if at all, from sea-water, gradually drains away, leaving but a thin pellicle incrusting the surface on which the mass was placed. Nevertheless these animated masses of sea-water exhibit a greater complexity of organisation than we should have expected from their gelatinous appearance ; and their beauty, when seen swimming near the surface in a bright day, is very great. They contain an abundance of thread- capsules, and many are even capable of stinging the human skin with these curious weapons, whence the name of " Sea-nettle " by which they are known in various countries. The name Acalepha, formerly applied to them in common with the other free-swimming gelatinous Radiata GENERAL CHARACTERS OF DISCOPIIORA — LUMINOSITY. 531 forming the two followiLg Orders, is derived from a Greek word signifying Nettles, and was employed to designate them by the ancient Greeks. The name of " Stang-fishes," by which they are also known in some localities, evidently alludes to their urticating powers. 1183. They almost always float near the surface of the water, advancing slowly by the flapping of their umbrella-like disc. They are seen both in the open sea and at the mouths of rivers, usually in vast numbers together, all moving in the same direction ; but none of them can endure a rough sea, and at the slightest disturbance they sink into the depths of the ocean. They are often driven by the winds and currents, which they cannot resist, against the hard shore, and there they are soon beaten to pieces by the waves ; or they are left dry by the tide, which they have not the power of following, and speedily melt like the spangled hoar-frost beneath the sunbeam. 1184. The voyager in the open sea, however, often encount- ers whole fleets of these and the allied animals of the next Order, extending as far as the eye can reach, basking as it were in the sunshine that illumines the surface, and reflecting its rays with all the gorgeousness of the most brilliant iridescent hues. Most of the Acalephae seem inclined thus to associate ; and in tropical regions, where they exist in the greatest abundance, the voyager, after passing through a fleet of one species, will in a short time encounter an equally extensive collection of another kind. It is not by day only, however, that these animals delight the eye of the mariner. It is chiefly to them that the phosphorescence of the sea is due, which is occasionally observed on our own coasts, but only in a degree which affords a faint idea of the extraordinary na- ture of this phenomenon as it presents itself in warmer latitudes. The whole surface of the ocean displays a diffused luminosity, like that of the Milky-way on a clear night. The path of the ship is marked by a brilliant line of glowing light. The waves, as they gently curl over one another (this phenomenon is never seen with a rough sea), break into brilliant spangles. The oars of a boat rowing over them, seem dripping with pearls when raised from the water ; and every stroke is marked with a new 532 PHOSPHORESCENCE OF THE SEA. line of brightness. And amidst this general splendour, varied forms of more glowing lustre are seen to move — some like ribands of flame, some like globes of living fire — some gently gliding through the still ocean, others more rapidly moving just beneath its surface. Now, although other marine animals such as the Pennatula (Fig. 717) and other Polypifera, the Pyrosoma (§ 1065) and other Tunicata — contribute to produce this daz- zling effect, it is principally due to the various species belonging to the group we are now considering. 1185. The diffused luminosity is given by minute species; and on our own coasts it seems to be principally due to the Noctiluca, a little animal much resembling a grain of boiled sago in size and appearance, which was formerly placed amongst the Acalephae, but is now generally regarded as a member of the lowest section of the Animal Kingdom, the Protozoa. The luminous secretion appears in all instances to become more vivid, when the animal is alarmed or stimulated in any way. Hence the disturbance of the water, by the gentle curling of the waves over each other, or by their ripple on the shore, is marked by lines of increased brilliancy. The movement of a boat, and the stroke of the oars, will have the same effect. If the animals be washed over the sands, they continue to display their luminosity in a fainter degree for some time ; but every footstep of a per- son who walks over them is studded with brilliant points. And if the hands be dipped in the water thus phosphorescent, and then rubbed together, they will be covered with luminous spots ; which, when examined, are found to be occasioned by the phosphorescent glow of these delicately formed little animals. There are few parts of the British coasts where this phenome- non is not occasionally witnessed. It generally follows a con- tinuance* of some particular wind; but the direction required varies in different parts of our island. It is thus that we obtain a more accurate idea of the vast amount of animals composing this tribe, than we derive from any observations that can be made during the day. Their bodies are often so transparent, that they can scarcely be distinguished from the water through which they are diffused, except when displaying their phosphorescence. But DISCOPIIORA ;— MEDUSA. 533 when the whole surface of the ocean, as far as the eye can reach, is seen to exhibit a uniform luminosity, and this is ascertained to be due to animals not larger than the head of a pin, in close apposition to each other, — the vast amount of organic life, which ordinarily escapes our notice, can scarcely fail to strike us with astonishment, not unmingled with pleasure at the thought, that each of these little beings is passing a life of enjoyment, and is performing an allotted function in the great oeconomy of Nature. 1 186. When we examine one of the larger Medusa (Fig. 723) as it floats in its native element, we find that the central part of the concave side of the disk is occupied by the stomach, in the A FIG. 723.— MEDUSA ; A, under surface, showing the mouth in the centre, surrounded by the tenta- cula, and the ovarial chambers exterior to the origins of these; B, side view, showing the tenta- cula hanging down in their natural position. middle of which is the mouth, opening downwards, and sur- rounded by four leaf-like tentacula. Around the stomach are four ovarial chambers, with separate orifices. These organs occupy the space inclosed, as it were, within the frame-work of the umbrella ; but the delicate membranous disk projects con- siderably beyond them, and floats freely in the water. Its margin is often lobed or fringed, and almost always provided with a variable number of slender tentacles, which are usually capable of contracting and elongatii^ themselves to a consider- able extent. The free portion of the disk is traversed by numerous canals, which arise either from the stomach itself or from a cavity situated immediately above that organ. Eight of these pass directly outwards, and terminate in a circular canal which runs round the edge of the disk, and in this eight small orifices are observed, serving for the discharge of foecal matter. 534 MEDUSA; RHIZOSTOMA. But another set of eight subdivide and ramify, so as to form a sort of net-work of vessels, which appear to serve for the nutri- tion of the portion of the structure at a distance from the stomach, and also to expose the nutritive fluid to the aerating action of the surrounding water. The Medusa often attain con- siderable size. It is said that their disks have been seen three or four feet in diameter ; and that the animals have weighed as much as 60 Ibs. It might be inferred from the extreme delicacy of their structure, that they are supported only on food most easily obtained ; but this is by no means the case ; for in their stomachs are found small Crustacea, Mollusca, and even Fishes. It would seem that their tentacula, like those of the Hydra, possess considerable muscular power ; and that they are capable of drawing towards the mouth almost anything which comes within their reach. Even large Fishes are occasionally found entangled amongst them. Very probably their stinging power is of use in weakening the resistance of their prey. 1187. There are many Discophora which resemble the Me- dusce in general form, but which yet differ from them in many important and curious points of organisation. Some- times the mouth is prolonged into a sort of proboscis, formed, as it were, by the union of the bases of the tentacula, so as much to resemble the stalk of a mushroom. Occasionally the oral tentacula almost dis- appear, and then the marginal tentacula are largely a4& abundantly developed, and probably replace them in function. The most curious modifica- tion, however, is that which is displayed to us in the Rhizostoma (Fig. 724), an animal bearing a close external resemblance to the Medusa. Here the central mouth is entirely absent ; but the tentacula are channelled through their whole length, and their FIG. 724. -RHIZOSTOMA. DI8COPHORA. 535 tubes open at their base into the stomach. At the free extremity, the tube of each subdivides and ramifies like the roots of a plant ; terminating in a number of small suckers, in the centre of each of which there is a small pore. It has been shown, by placing one of these animals in a coloured fluid, that solid particles, if sufficiently minute, may enter these pores ; but this species must either be nourished by extremely minute animalcules, or by im- bibing the juices of other animals, upon which it fixes its suckers. 1188. According to Ehrenberg, a nervous circle may be de- tected surrounding the mouth in some animals of this group ; and imother, connected with the first, running round the margin of the disk. Upon this point, however, there is considerable doubt. The animals of this group appear very little sensitive to injurious impressions. They give no signs of feeling the deepest and most extensive wounds of their surface ; and the movements of contraction and dilatation have been seen in parts of the disk almost separated from the rest, as well as in the entire animals when nearly two-thirds of their bulk had been lost by the draining of their fluids. In such instances, the move- ments may be re-excited after they have ceased, by friction and by punctures of the fibrous substance, just like those of the heart and alimentary canal in the higher animals ; and they would seem to be of an equally involuntary character. 1189. Round the edge of the disk, however, we find a series of curious bodies which have generally been regarded as organs of vision and hearing. The supposed auditory organs, which are situated in the bulbs at the base of the marginal tentacula, are small vesicles containing one or more spherical or oval cal- careous concretions. The ocelli, or supposed visual organs, con- sist of small aggregations of pigment-cells, surrounding a small crystalline refractive body, which is said to be of a silicious nature. From the characters presented by these ocelli, the late Professor Forbes proposed to divide the Medusae into two great groups, which appear to correspond in a remarkable manner with the peculiarities in the mode of development of the animals. In one of these the ocelli are always placed in notches between the marginal tentacles, and the membranes in their vicinity are 536 DISCOPHORA ; — DEVELOPMENT. so modified as to produce a more or less complicated hood or covering for the eye. These are called Steganophthalmata, or Covered-eyed Medusce; they are the largest and most highly organised forms of the Order, and their vascular system exhibits a very complicated series of ramifications. In the other section the ocelli, or a part of them, are always placed at the base of the tentacles, and they are never provided with membranous cover- ings ; hence they have received the name of Gymnophthalmata, or Naked-eyed Medusce. They are generally of small size, and their vessels, with very few exceptions, run straight from the centre to the margin of the disk, and never display the same amount of ramification as in the covered-eyed species. In some of them the ovaries are situated in the lower part of the umbrella, in the course of the vessels. 1190. As already indicated (§ 1165), it is in their mode of development that these elegant creatures exhibit most clearly their close relationship to the stationary Hydroid Polypes. With very few exceptions, the eggs of all the Discophora give origin to creatures which in every particular of their structure agree with the characters of the Hydroida, and it is only by a subse- quent process of budding or self-division that the latter again produce the likeness of their free-swimming parents. It was from the observation of these phenomena in the reproduction of the Medusaa that Steenstrup was led to put forward the law of the so-called "Alternation of generations," which has since found applications in so many other groups of animals. In the higher or covered-eyed Medusas, the ciliated embryo (a) re- sembles that produced by the Hydroid Polypes, and like it swims about for a time, and finally attaches itself by one ex- tremity (b). The opposite extremity becomes much widened in proportion to the adherent base, and developes a considerable number of tentacula (c, d), when it closely resembles a Hydrj, and was formerly regarded as a marine form of that genus. At this period it frequently gives birth to young Polypes, in pre- cisely the same way as the Hydra (d). In course of time the body becomes considerably elongate 1, and appirently divided into segments by transverse constrictions (e); these gradually DISCOPHORA ; — DEVELOPMENT. 537 become deeper, their edges display eight notched processes (/), and as the separation grows more and more distinct, the seg- ments at last resemble a pile of jagged saucers placed one upon another. Finally these segments separate from each other and FIG. 725.— DEVELOPMENT or MFDUSA. swim away freely, when they present a conformation somewhat resembling that of a Medusa, although the notched processes give it the appearance of an eight-rayed star. By degrees these shorten until the disk becomes nearly circular, when the mouth and other organs belonging to the stomachal peduncle make their appearance in the centre (#) ; the buccal tentacula are afterwards developed, a^nd the animal soon acquires its ma- ture form. — In the naked-eyed Medusae, as far as our present knowledge extends, the Polype produced from the ciliated embryo is of the Tubularian type, and the Medusae are produced by true gemmation from the neighbourhood of the tentacula. They first appear in the form of small rounded knobs, which in- crease in size, and acquire more and more of the form of the Medusa; the pedicle by which they are attached to the parent Polype at the same time grows thinner by degrees, until, when the Medusa has attained its perfect form, it drops away from its point of attachment, and swims freely through the water. In some cases, however, there is a direct production of Medusae from Medusae, either by gemmation or by ova. Thus 533 CTENOPHORA ;— CTDirPE. in some species of the genera Lizzia and Sarsia, belonging to the naked-eyed group, young Medusae are produced from buds formed either from the stomachal peduncle or from the bases of the tentacles ; whilst in a few species, one of which is the common Pelagia noctiluca of the Mediterranean, it has been found that the ova produce Medusas directly, without the in- tervention of any polypoid form. ORDER III.— CTENOPHORA. 1191. Of the Order Ctenophora we have an interesting ex- ample in the little Cydippe, which is often abundant on our own coasts. This animal is of a nearly globu- lar form, sometimes a little elongated at the two extremities, and about three- fourths of an inch in length. It is com- posed of a delicate jelly-like substance, strengthened by eight bands of somewhat firmer texture, which run like meridian lines from pole to pole. These bands are covered with rows of large cilia, arranged side by side, so as to form narrow plates of a fin-like character. There are, in the most common species, from three to seven cilia in each row ; and about twenty rows on each ridge. The whole ridge is not unlike the paddle-wheel of a steam-boat ; but the motion is given by the vibration of the separate floats, and not by the revolution of the whole. Over these floats the animal has evidently complete control; it can retard or stop their move- ments at pleasure ; and arrest the play of one, two, or more rows whilst the remainder continue in rapid vibration. By these means it is capable of swimming through the water with consider- able activity, and of changing its course at will. The animals themselves are of a bright faintly-blue aspect; and the cilia present vivid iridescent hues when in motion. The mouth is situated at one of the poles of the globe, and it is always di- rected forward when the animal is in motion. It is a wide en- TIG. 726.— CYDIPPE. a, a, tentacula ; b, mouth ; c, termination of intestine. CTENOPHORA ;— CYDIPPE. 539 trance to the short oesophagus, which terminates in the stomach ; it can be closed by the animal when irritated ; but when freely swimming through the water, it is always widely dilated. From the stomach, there passes a narrow straight intestine, which terminates at the opposite extremity of the body. When the animal is in active movement, therefore, a continual stream of fluid will enter its mouth, and will pass out again behind ; and from the minute particles contained in this fluid, its nourishment is probably in part derived. 1 192. These apparently powerless little animals feed, however, like the Discophora, upon species of much higher organisation and firmer texture ; and they are provided with similar means of obtaining them. From the vicinity of the mouth arise two filaments or tentacula, which are many times its own length. These are provided with lateral filaments, which arise at regular intervals from one side along their whole course, and are spirally coiled like the tendrils of a pea. The principal filaments do not arise from the surface of the body, however, but from the bottom of two deep cavities extending into its interior. Into these cavities the main filaments with their appendages can be entirely retracted. The lateral fibrils seem to contract spirally towards the longitudinal filaments ; and the latter are drawn by irregular contractions into the cavity, so as to be entirely concealed. When the animal wishes to put them forth, it seems to contract the cavity, and the filaments are jerked forth, as it were, not simul- taneously, but first on one side and then on the other. When the main filaments have been ejected from the body, the little tendrils begin to uncoil. When one of these beautiful little animals is placed in a vessel of sea-water, it sometimes remains at the bottom, projecting its long filaments upwards. At other times it darts upwards with great velocity, drawing its long fila- ments after it, retracting and extending them alternately. Not unfrequently it remains for some time at the top of the water ; and, when it wishes to descend, it turns over, drawing up its filaments suddenly, and then swims, mouth downwards, to the bottom of the vessel. The filaments contain a great quantity of thread-cells analogous to those of the other Radiata. They exist 540 CESIUM VENER1S ;— SIPHONOPHORA. in the majority of the Order, but are wanting in the Beroe and its allies, which resemble the Cydippe in general form. 1193. The Cesium Veneris, or Girdle of Venus, belonging to the same group with the preceding, is a flat riband-shaped animal, which sometimes attains the length of five or six feet, whilst its breadth is not more than as many inches. At first sight the form of this species might forbid us from ranking it near the Cydippe. When we examine its structure, however, we find that there is a much greater real correspondence than would have been suspected. The mouth is placed, not at one extremity, but at the centre of one of the sides. The alimentary tube passes straight across the body, and terminates on the opposite side ; the digestive organs closely resembling those of the Cydippe. The edges of both sides are fringed with cilia from one end to the other ; and it appears to be by the vibra- tions of these cilia, rather than by any movement of the body itself, that it is propelled through the water. As in the Cydippe, a system of vessels absorbs the nutritious fluid produced by the action of the digestive apparatus, and conveys it to the remain- der of the structure, here so remote. And here, also, we find a part of these vessels running under the ridges bearing the cilia, as if to expose the fluid they convey to a stratum of water con- tinually renewed by the ciliary action. We might then regard this animal as a Cydippe, flattened and extended in a lateral direction ; and many very interesting forms of transition have been discovered, which show that this view of its structure is the true one. ORDER IV.— SIPHONOPIIORA. 1194. The Siphonophora are free-swimming compound ani-* mals, which appear to be nearly allied to the Hydroid Polypes. They present two very distinct types of structure, however, one of which, that of the Physograde, or Hydrostatic Acalephce, is characterised by the presence of one or more large air-sacs, by which great buoyancy is given to these beautiful animals. It SIPHONOPI10KA ;— 1'iiYSALIA. 541 would appear that they have considerable power over these or- gans ; either forcing out the air contained in them, or compress- ing it into a much smaller compass, when they wish to sink ; and distending the sac by some unknown means when they desire to rise. We seldom meet with anything like radial symmetry in this group. The forms of the species are extremely variable and irregular ; but there is usually a correspondence between the two sides of each individual. A well-known example of this group is the Physalia utriculus, commonly £ termed the Portuguese Man-of-war. This possesses a single large air-sac, which is surmounted by a sort of crest (b), possessing a greater degree of firm- ness than the rest of the structure, and elevated entirely above the water, when the animal is floating at the surface, so that when exposed to the influence of the gentle breeze, the animal is wafted by its means from place to place. The air-sac itself possesses considerable mus- FIG. 727.— PHYSALIA. cular power. It is provided with two orifices («, c), one at each extremity, through loth of which air is forced out when the bag is compressed by the hand ; each of these orifices is provided with a little circular muscle, which usually keeps them closed, but which allows of their dilatation during the continuance of the o itward flow of air. It is not improbable that the alteration in the specific gravity of this animal required for its sinking in water, is effected partly by the explosion of air in this man- ner, and partly by the compression of the remainder. Beneath the air-sac there is a mass of short flask-shaped appendages, which hang down from the under side of the air-sac, and are terminated by suckers, with an orifice in each. These are re- garded as the individual Polypes of the structure. Whilst the lower surface of the air-sac is not itself above six inches from one end to the other, the tentacu a sometimes hang down like fishing- lines, to an extent of sixteen or even eighteen feet. They gen: ra.ly possess an active stinging power, and are also very TOL. IT. PP 542 SIPHONOPHORA ; — VELELLA. contractile, so that they are able to draw the prey which they have attacked towards their point of origin. This animal is one of those most commonly observed by voyagers, sailing in fleets upon the calm surface of the ocean, and disappearing with great rapidity when alarmed by the roughness of the waves. 1195. The Chondrograda, or Cirrigrade Acalephce, are dis- tinguished by the possession of an internal skeleton, in the form of a cartilaginous plate imbedded in the soft disc which forms the upper part of their bodies. This plate is cellular in its structure, and its cells are filled with air, — an arrangement by which the animal is assisted in floating at the surface of the water. Amongst the most remarkable forms of this group is the Velella, in which the disc is furnished with a delicate crest of a sub- cartilaginous texture, which serves as a regular transparent sail when the animal floats at the surface of the sea. One species of Velella is found on the Irish coasts. CHAPTER XXVI. OF THE PROTOZOA. 1106. THIS, the lowest division of the Animal Kingdom, in- cludes a multitude of minute creatures, of an exceedingly simple structure, in which no traces of many of the organs which we are accustomed to see in an animal can be detected even with the highest powers of our microscopes. Ehrenberg, indeed, at- tributed a very considerable complexity of organisation to them, but the researches of subsequent observers have shown that in many cases the learned Professor of Berlin was in error ; and most of the Naturalists of the present day have been inclined to regard them as consisting, like the lowest plants, of simple cells endowed with an independent vitality. It is, however, difficult to understand how all the properties possessed by these creatures should really appertain to a simple cell, and of late there has been a tendency to doubt their unicellular nature. The con- sideration of these views will, however, be best left until we come to treat of the Infusoria, the most highly organised group of the Protozoa. 1197. It may be stated, however, that the gelatinous mass of which the Protozoa are composed, which has been denominated sarcode by M. Dujardin, exhibits small vacant spaces in differ- ent parts of its substance ; these are called vacuoles, and were taken for empty stomachs, by Ehrenberg and other observers. Imbedded in their walls there is always a dark body called the nucleus, and one or more clear pulsating spaces, or contractile vesicles, which appear in many cases to be connected with a system of vessels serving for the circulation of fluids. Many possess a mouth and oesophagus, but there is no distinct alimentary canal, although the foecal matters are frequently discharged from 544 GENERAL CHARACTERS OF PROTOZOA. a particular spot, which may be regarded as an anus. Their reproduction usually takes place by a division of the substance of the creature itself; sometimes, as in the Hydra, by a process of gemmation, whilst in some instances a production of germs by the division of the nucleus has been observed. 1198. It is in these animals that we find the nearest approach to the vegetable kingdom ; in fact, the lowest of the Protozoa approach so closely to the most imperfectly organised plants that it is at times difficult to say to which kingdom of nature a crea- ture may belong. Many of the organisms included by Ehrenberg amongst the Infusorial Animalcules, which constitute the most important class of the Protozoa, have been since proved to be- long to the vegetable kingdom ; and the researches of Mr. Carter, of Bombay, go far to show that under certain circum- stances the sarcode-like parenchyma of particular plants may acquire an appearance and behaviour so like those of some Protozoa, as almost to render it doubtful whether any boundary can ever be established between the two kingdoms of organic nature. 1199. Almost all these creatures are inhabitants of water, only a few being found as parasites in the viscera of other animals. They exhibit both simple and compound forms, and in some of the latter the union of the individuals is effected by exceedingly curious means, and accompanied by remarkable phenomena of community such as we meet with in no other group of animals. Many of them have the power of secreting a shell or case, which is either of a horny or calcareous nature ; the remains of the latter occasionally constitute the greater part of large beds of rock. 1200. The Protozoa may be divided into three Classes :— I. INFUSORIA, or Infusorial Animalcules, so called from their having been first discovered in vegetable infusions ; they have a firm integument, furnished with cilia by which they swim through the water, and nearly all of them take their food through a mouth, which communicates by a short oesophagus with the cavity in their interior. II. RHIZOPODA, in which the body appears to consist of nearly INFUSORIAL ANIMALCULES. 545 homogeneous gelatinous matter, and the surface is destitute of cilia, the movements being effected by the extension and con- tractions of processes or filaments of the general substance, and the food taken by the same means. III. POUIFERA, or Sponges, compound animals consisting of a horny or silicious framework, covered by a gelatinous fluid, which contains a multitude of minute creatures resembling the Rhizopoda in their characters. They form masses of various sizes and forms, permeated by larger or smaller canals, which •Mlow the water to pass to all parts of them. CLASS I.— INFUSORIA. 1201. Whenever any decaying organised matter exists in a fluid state, and is exposed to air and warmth, it will speedily be found peopled with minute inhabitants of the most varied forms and diversified movements, possessed of considerable activity, and evidently endowed with an energetic system of nutrition. The cause of the sudden appearance of these Ani- malcules where no germs were previously suspected to exist, and where it was not easy to suppose that they had been con- veyed, has been a matter of much speculation. Many have had recourse to the supposition that the germs formed part, in a latent state, of the living tissues of the animal and vegetable structures, from the decomposition of which they were evolved ; and others have even supposed them to have arisen from acci- dental combinations of inorganic elements. But these Animal- cules are not confined to infusions of organised matter ; they are found in the stagnant waters around our cities ; in the waters of rivers, harbours, and lakes ; and even, it is believed, in every fluid drop of the ocean. From their minute size and almost universal distribution, therefore, we cannot doubt that they are by far the most numerous living beings which exist on the face of the globe. Indeed, from calculations it would appear that a single cup of water may easily hold a number of the smallest 546 INFUSORIAL ANIMALCULES. known species, far surpassing that of the whole human popula- tion of the earth. 1202. The forms presented by these Animalcules are ex- tremely various. In some there is a considerable variety in the forms assumed by the same individual under different circum- stances, but still a prevailing shape can be recognised. ID FIG. 728.— VARIOUS FORMS OF ANIMALCULES. others, again, the body, although still unprotected by any firn, envelope, appears to undergo little change in figure, except when affected by some temporary pressure. But there are many species which cannot be influenced even by this; their soft bodies being enclosed in a delicate but firm integument, strengthened by a deposit of silicious matter. These are termed loricated Infusoria ; and these envelopes, which are often pre- served after the death of the animals, are termed their shields or sheaths. 1203. Although most of the Infusoria have the power of freely moving through their native element, some occasionally attach themselves to a solid base, like Polypes ; but many, like the Hydra and Sea- Anemone, have the power of occasionally detaching themselves, and go in search of a new field for the supply of their voracious appetites. The analogy to the Poly- pifera is very strongly marked in some species, however, in which we not only observe the Animalcules attached during nearly the whole of life, but find a large number associated into one plant-like structure. In all, the body is furnished more or INFUSORIAL ANIMALCULES. 54/ less abundantly with cilia, which serve various important pur- poses. Sometimes they are only disposed around the mouth, towards which they produce a vortex of fluid, that brings a sup- ply of alimentary particles. Where the digestive cavity has a separate termination, this also is usually fringed with cilin, by the action of which the particles rejected are thrown off to a distance. And, in many of the higher species not enclosed in a silicious envelope, the whole body is beset with rows of these little filaments ; by the action of which every possible variety of movement seems to be produced. 1204. The name Polygastrica was applied to these Animal- cules by Ehrenberg, in consequence of his belief that they possess a large number of distinct stomachs, or cavities for the reception and digestion of aliment. This belief is founded on the appearance which many of them present, when they have been allowed to remain for a short time in water, in which finely divided particles of colouring matter are suspended. The par- ticles are observed to be drawn towards the mouth, by the action of the cilia with which most of them are provided ; and before long, the whole of the transparent body is seen to be studded with coloured globules of a uniform size, many times larger than the separate particles themselves. Sometimes these globules are very numerous, amounting to more than one hundred. If two kinds of colouring matter be put into the water, as for in- stance carmine and indigo, separate pink and blue globules will be seen in the bodies of some of the Animalcules. 1205. From these facts it was inferred by Ehrenberg, that a large number of globular cavities exist in the substance of the body, into which the food is received. He considers that sometimes these communicate only with the mouth, as in the Monas ; but that in general they are arranged along an intestinal tube into which they open by a short neck. The course of this tube he infers from the disposition of the coloured globules, rather than from any more distinct indication of its presence. Thus in the Vorticella, he thinks that it returns to the neighbourhood of the mouth ; whilst in Enchelys and Leucophrys it terminates at the opposite extremity of the body, — running straight in the first from one end to the other, and in the second making two 543 INFUSORIAL ANIMALCULES spiral turns in its passage. He does not affirm that he has ever distinctly seen food passing along this narrow intestine ; or that he has been able to trace the walls of the globular stomachs, any more than of this alimentary tube, when they are not filled out with colouring particles. 1206. The views of Ehrenberg were never by any means universally received amongst Naturalists ; and it is now admitted by all who have paid attention to the structure and habits of the Infusoria, that they are very erroneous. A kind of circula- tion is seen to be performed by the globular masses already men- tioned, as if they floated loosely in the cavity of the Animalcule, and did not form part of the supposed alimentary canal. And it has been found that, when a small quantity of an alkaline solution is allowed to touch their bodies, they burst, and discharge these globules, which seem to have been imbedded in a soft gelatinous substance. 1207. According to the views which have been lately put forward with considerable appearance of truth with regard to the organisation of the Infusoria, these microscopic creatures are neither to be regarded as simple cells, nor as endowed with a complicated system of alimentary and other organs, such as were ascribed to them by Ehrenberg and his followers. They ap- pear to consist of a gelatinous envelope of greater or less thick- ness, containing in its substance the nucleus and contractile vesicle already mentioned (§ 1 197), and enclosing a large cavity, which may be considered as a stomach. Access to this is usually provided by means of a mouth and a short O3sophagus, into which the minute particles of alimentary matter are carried by ciliary action. By the same agency they are conveyed to the bottom of the cesophagns, where they are gradually collected into a ball, and this when sufficiently large is allowed to pass into the gelatinous fluid with which the stomachal cavity is filled. Here the nutritive material is extracted from them whilst they circulate in the cavity in the manner above described. 1208. Putting aside the undetermined question of the in- terior organisation of the digestive apparatus, we may pass to the consideration of other phenomena presented by this remark- able class. Food is usually conveyed to the mouth by the vibra- INFUSOKIAL ANIMALCULES; THEIR MOVEMENTS. 549 lion of the cilia which surround it ; in this manner a vortex is produced in the fluid, which brings the particles floating in it, or other Animalcules swimming in its neighbourhood, within the grasp of the lips of that aperture. In one genus, Nassula, there is a very curious dental apparatus, for the prehension and re- duction of food. This consists of a sort of cone, formed by a large number of diverging flexible bristle-like organs, at the apex of which the mouth is placed, whilst the base can be projected and expanded so as to inclose the prey, over which it then con- tracts by the approximation of these curious teeth ; these, al- though flexible, appear to possess considerable firmness. 1209. It is to the cilia, also, that the movements of the greater part of the animalcules, which swim freely through the water, appear to be due. These movements are extremely various in their character in different species ; and when a number of dissimilar forms are assembled in one drop of water, the spectacle is most entertaining. Some propel themselves directly forwards, with a velocity which appears (when thus highly magnified) like that of an arrow, so that the eye can scarcely follow their movement ; whilst others drag their bodies slowly along, like the leech. Some make a fixed point of some portion of the body, and revolve around it with great rapidity ; whilst others scarcely present any appearance of animal motion. Some move forwards by a uniform series of gentle undulations or vibrations ; whilst others seem to perform consecutive leaps, of no small extent compared with the size of their bodies. In some instances the body is furnished with stiff bristles and hooks, by the agency of which the Animalcule is enabled to run and leap upon the stems and leaves of aquatic plants. In short, there is scarcely any kind of movement, which is not practised by these Animalcules. They have evidently* the power of steering clear of obstacles in their course, and of avoiding each other when swimming in close proximity. By what kind of sensibility the wonderful precision and accuracy of their movements is guided, is yet very doubtful. The general surface, in those whose bodies are not inclosed in a firm envelope, appears very sus- ceptible of impressions. No organs of special sensation, however, can be detected; except certain red spots observable in the 550 INFLUENCE OF LIGHT AND HEAT ON ANIMALCULES. bodies of many species, which are believed by Ehrenberg to be eyes. This belief rests only upon an analogy which may very possibly be unfounded. There can be little doubt, from their position and their similarity to the undoubted visual organs in the class nearest allied to them, that the red spots on the neck of the Rotifera (§ 929) may be fairly regarded as eyes. But the same arguments by no means hold good in regard to the Infusoria. 1210. Light has certainly, however, a considerable influence on these Infusoria, both in regard to their first production and their subsequent movements. It has been found that they will appear much more speedily in an infusion exposed to light, than in one secluded from it. But there are some species which can exist in almost total darkness ; being found in the recesses of the deepest mines. And it is further observed, that a very powerful light is injurious to them, and that they seek to avoid it ; this may be due, however, to the heat which accompanies it, of the influence of which they are very susceptible. The greater number are instantaneously killed by a moderate heat, which acts equally upon both ova and adults ; but they can support it better if the temperature be raised gradually. There are a few species which can support a temperature of 120°. On the other hand, cold is very injurious to these Animalcules: but it affects the adult more than the germ. If the water in which they exist be suddenly congealed, they are usually killed within two hours ; but they are at first able to develope heat enough to prevent the freezing of their own bodies, as appears from the small quantity of water which remains fluid around them. If the congelation be gradual, however, they retreat beneath the surface, so as not to be included in the coating of ice ; and in the winter, therefore, we meet with them just below the frozen covering of the waters whidi they inhabit. Even if they are entirely inclosed, and the greater part of them destroyed, it is seldom that one or two individuals do not remain, — the eggs being preserved where the parents have perished ; and from these a new population, as great as the previous one, will speedily originate at the return of the genial warmth which calls them into active life. 1211. The presence of Oxygen in the atmosphere, with POLYGASTRIC ANIMALCULES. 551 which the water they inhabit is in contact, is necessary to the continued life of Animalcules. But this may he in very small amount. Many species will live in water placed under the receiver of an air-pump, from which the greater part of the air has been removed. Others are not killed for a long time, by the interposition of a stratum of oil between the water and the air above. The microscopic observer well knows that he can keep most kinds of Animalcules for several days in a drop of water, flattened between two pieces of glass, so that it is only in con- tact with the air at its edges. But if some other gas be substi- tuted for atmospheric air, a positively injurious effect results; when a vessel was three-parts filled with water containing Animalcules, and the remaining fourth was filled with hydrogen, they died within seventeen hours. 1212. Animalcules are very susceptible of the influence of Electricity. A spark drawn through water inhabited by them, usually destroys all those that happen to be in its current ; and this is the case whether the Electricity be generated by an electric machine, by a galvanic pile, or by a magnetic appara- tus, provided that the current be of sufficient intensity to decom- pose water. These beings are also readily acted upon by various substances, which are soluble in water, or which can otherwise act upon them in a fluid form ; but the susceptibility to such influences varies with the species. Tims Animalcules inhabiting fresh-water are killed by a single drop of sea- water, which may nevertheless be full of other species peculiar to it. Alcohol usually destroys the inhabitants of fluids to which it is added even in small quantities ; sugar has the same effect on many species ; and strychnine on all. On the other hand, substances which are only mechanically suspended, or but slightly soluble in water, such as arsenic, appear to have little or no influence, even when their particles are swallowed ; and calomel, corrosive sublimate, and camphor, are not fatal until some hours have elapsed. 1213. The universal presence of Animalcules in fluids con- taining organic matter, and exposed to the air, joined to the suddenness of their appearance under particular circumstances, has led to the belief that they are generated by the decomposition 552 REPRODUCTION OF INFUSORIAL ANIMALCULES. of the animal or vegetable particles, which thus consisted, as it were, of their latent germs. But this hypothesis is unnecessary to account for the phenomena ordinarily observed ; and it is inconsistent with ascertained facts. Many of the Infusoria have the power of inclosing themselves in a firm cyst, and they avail themselves of this mode of protection when the pools in which they have been living are dried up by the heat of the sun. By this means they are enabled, like the Rotifera (§ 931), to support drought without injury ; and in this manner both they and their germs are probably carried about, in the form of minute particles of dust, ready to develope themselves in any spot which may af- ford them the requisite moisture and nutriment. In this respect they probably resemble the Fungi, whose germs are known to be thus diffused (VEGET. PHYSIOL. § 50 — 64). 1214. The extraordinary powers of reproduction possessed by th se Animalcules, will fully account for their rapid multi- plication, when once they have obtained the means of develop- ment. Several modes of propagation are observed among them. Not unfrequently we observe, as in the Vorticella (§ 1217), a reproduction by buds developed from the side of the body, as in the Hydra. In other species, again, the process of generation is accomplished by the separation of the body into two parts : the division, which may be observed in several stages of its pro- gress, is sometimes transverse (Fig. 728, b\ sometimes longitu- dinal (c), sometimes oblique. In other tribes propagation takes place by ova or germs evolved within the body of the parent, the greater part of whose bulk is often made up by them. Fre- quently the Animalcules secrete a gelatinous matter from their surface, which hardens and becomes a sort of cyst, within which a division of the substance of the body takes place, a portion of the nucleus going into each segment ; or the nucleus itself alone breaks up into numerous germs. According to some observa- tions made by Professor Stein, which, however, have since been disputed, some of the most highly organised Infusoria (the Vorticellce) give rise to animals which resemble the Rhizopoda in their power of throwing out gelatinous filaments from various parts of their bodies, and these again produce young Vorticellce INFUSORIAL ANIMALCULES ;— MONADS.' 553 in their interior. By these methods, sometimes employed singly, occasionally in combination, a single individual may soon become the parent of an immense population. Thus the Paramecium aurelia, if well supplied by food, has been observed to divide itself every twenty-four hours ; so that in a fortnight, allowing the product of each division to multiply at the same rate, 16,384 animalcules would be produced from the same stock; and in four weeks, 268,435,456 new beings would result from a con- tinued repetition of the process. But this animalcule has occa- sionally been observed to increase with much greater rapidity ; the first million being produced (according to calculation based on fair data) within seven days. 1215. In some Infusoria no mouth has yet been detected, and it is supposed that they must derive their nourishment by simple absorption through their external membrane. Of these the Euglence are a very abundant form, occurring frequently in such numbers in stagnant waters, as to give these a green or red colour. They possess a considerable power of changing their form, and are usually provided with a red eye-spot. The Peridinium, another form of mouthless animalcule, is enclosed in a curious silicious carapace, which is usually furnished with pro- jecting spines and curved processes. The Opalince are flat, elliptical creatures, with the surface covered with oblique lines of cilia. They are found in the intestines of Frogs and Worms. 1216. The Monads constitute the smallest of the Infusoria. They usually present an oval form ; and seem like moving points of gelatinous matter. They swim freely and with activity, apparently by the vibrations of a sort of filament, which is said to be tubular. The number of coloured particles seen in their bodies, when the fluid in which they live has been tinged for the pur- pose, is usually small ; in many species never above four or six. They only seem to possess one orifice to the digestive cavity; and from their extreme minuteness no cilia can be detected in its neighbourhood, though it is probable that such exist there. Of the animalcules included in this family, some have a tendency to aggregate themselves in clusters ; and it is probable that those which thus unite pass the earlier part of their lives in a separate 554 INFUSORIAL ANIMALCULES 5—VORTTCELLINJE. condition. It is often very difficult to distinguish the Monads from the young of other species, which they much resemble. Where a number of minute gelatinous points are seen in the neighbourhood of clusters of larger forms, they are probably to be regarded as their germs in a state of development. 1217. The Vorticell'mcB are a very interesting family to the microscopic observer, from the variety of their forms and actions, and from their great abundance in most pools in which vegeta- tion is going on. The ciliary action is here very distinct and powerful; and the Animalcules show by their movements a great susceptibility to external impressions. Thus, the common Vorticella (Fig. 728, a\ which clusters round the stalks of duck- weed, is usually attached by a long peduncle, which, when the animal is seeking for its prey by the vibration of its cilia, seems fully extended, and almost put on the stretch. But if the stage of the microscope be smartly tapped, the Animalcule is seen to contract its peduncle suddenly ; and it afterwards slowly extends it when free from alarm. In the Stentor (Trumpet Vorticella), which is one of the largest of the Polygastrica, the body is itself prolonged, and attached at its basis. In the Vaginicola, each animalcule is enclosed in a delicate horny sheath, within which it can retract itself at pleasure ; and the Ophrydium, another allied form, constitutes large gelatinous masses, in which a vast multitude of animalcules are imbedded. The true Vorticellce are able to change their dwelling-place in a singular manner. A fringe of cilia is produced at the lower part of the body, and when this is complete, the animal quits its stalk, and swims away freely in search of a new point to which to fix itself. Some of them produce buds from their sides, like the Hydra ; and others multiply by subdivision. Both these processes take place, if the temperature be genial, and the animals be well supplied with food, with great rapidity. By the older observers, those which were seen during their change, and whose form was thus very different from the one usually observed, as also those that were seen in their unattached condition, were regarded as dis- tinct species. In some genera belonging to this group, we ob- serve the stalks of a number of individuals proceeding from one INFUSORIAL ANIMALCULES ;— RHIZOPODA. 555 common stem ; and sometimes this ramifies and subdivides, so as to exhibit a completely arborescent form, analogous to that of the Polypifera. The circular arrangement of the cilia around the mouth, and the mode in which these organs are employed in obtaining food, has occasioned the Vorticellce and the Wheel- Animalcules to be confounded together. 1218. The principal families which have been lately eliminated from the Infusoria, and transferred to the Vegetable Kingdom, are the Volvocinece and the Bacillarice. The former are globu- lar organisms, which may be commonly found in ponds, moving slowly through the water by the agency of numerous filaments which project from little green points upon their surface. The Bacillarice, or Diatomacece, are furnished with silicious shields, and are usually found united into filaments of various forms. They are especially interesting from the vast accumulations of their shields which are found fossil in different parts of the world, whole beds of earth, and even of stone, being almost ex- clusively composed of their microscopic remains. CLASS II.— RHIZOPODA. 1219. In the animals forming the second class of the Pro- tozoa, the general organisation, as f^f as it can be made out, appears to be very similar to that of the Infusoria ; but we find no trace of a firm external layer, bearing cilia, such as occurs in most of the species of the preceding class. On the contrary, the whole body appears to consist of a homogeneous mass of jelly, capable of extension in various directions ; and the only internal organs that can be detected, are the contractile vesicles and the nucleus. 1220. The best-known of these Animalcules is the Amoeba diffluens, called the Proteus by microscopic observers, a small gelatinous creature, which is found in our fresh waters. Its movements are effected by throwing out processes from any part of its body ; these appear to act as feet, and the little mass of 556 RHIZOPODA ;— FOR AM IN IF ERA. jelly advances slowly by their agency in any required direction. In feeding, the Amcp.ba, destitute of a mouth, attaches itselt to the body which it is desirous of appropriating, and by the slow extension of its substance gradually envelopes the morsel of food, which is often so large that the gelatinous matter of the Amceba only forms a thin coat over it. In some allied species, such as Actinophrys, the processes thrown out are delicate fila- ments, and these appear to have the power of adhering firmly to any passing Animalcule, which is speedily drawn down to the surface of the gelatinous body of the Rhizopod, and enveloped by it in the manner above described. Some other fresh-water Rhizopoda have the power of secreting a little horny shell, which serves for the protection of the animal, leaving a small aperture at one extremity for the protrusion of the gelatinous processes or filaments. 1221. The marine forms are "generally compound, a number of these delicate gelatinous creatures being intimately associated together. They are always inclosed in delicate calcareous shells, divided into chambers corresponding in number with the indi- vidual Rhizopods of which the colony is composed ; from the strong resemblance which some of them bear to the chambered shells of some Cephalopoda (§ 976), they have been supposed to be formed by animals of that class. Many kinds of them exist on almost every sandy shore ; but their extreme minuteness causes them to be usually overlooked, and is also an obstacle to the satisfactory determination of the character of the animals which construct them. By D'Orbigny, who first attracted the atten- tion of Naturalists to the details of this curious group, it was regarded as an Order of Cephalopoda ; and he gave to it the name of Foraminifera, on account of the communication between the chambers not being established by one principal tubular aperture, the siphuncle, but by numerous minute foramina or porous orifices. The species which exist on the shores of Northern Europe are so minute, as not to be easily examined, even with the microscope ; but those which are found in the Adriatic Sea are sufficiently large to be recognised with the naked eye. FORAMINIFERA ;— NUMMULITES. 55/ 1222. If we merely consider this group as it presents itself to our notice in the existing epoch, we should have but a very imperfect idea of its importance. The forms under which it once existed in much greater abundance, have been preserved to us ; and recent inquiries have added to our knowledge of these in a most astonishing degree. The fossils termed Nummulites have long been observed to bear a large share in the formation of extensive beds of limestone rock. They were remarked by Strabo in the stones of the Pyramids ; and he informs us that they were commonly reputed to be the petrified impressions of the lentils, which had been used as daily food by the workmen engaged in building them, and takes some pains to refute this idea. By subsequent authors, these Nummulites have been supposed to be the opercula (§ 971) of the Ammonite (§ 969), which, it was imagined, might probably form a new one, every time that it added a chamber to its shell. The discovery, however, of minute shells of a similar character at present existing, and evidently belonging to distinct animals, established their claim to a similar position. Nummulites are probably the largest forms of this group ; some of them measure about an inch and a half in diameter, whilst a great proportion of the rest are microscopic. Many limestone strata of the tertiary period, are almost entirely composed of the larger Nummulites ; and these strata constitute the principal part of several mountain ranges in Southern Europe, such as the Alps, Carpathians, and Pyrenees. The Sphinx, as well as the Pyramids, are composed of a limestone loaded with Nummulites. — A more minute shell, the Miliola, of the same description, but no larger than a millet- seed, bears an equal proportion in the mass of limestone strata which are quarried near Paris. fc* We scarcely condescend/'* observes Lamarck in reference to this fact, " to examine micro- scopic shells, from their insignificant size ; but we cease to think them insignificant when we reflect, that it is by means of the smallest objects that Nature everywhere produces her most remarkable and astonishing phenomena. Whatever she may seem to lose in point of volume in the production of living bodies. VOL. II. Q Q 558 FORAMINIFERA OF CHALK. is amply made up by the number of the individuals, which she multiplies with admirable promptitude to infinity. The remains of such minute animals have added much more to the mass of materials which compose the exterior crust of the globe, than the bones of Elephants, Hippopotami, and Whales." 1223. But these facts sink into insignificance, when compared with those lately revealed by the researches of Ehrenberg, in regard to the existence of a race still more minute, and its multi- plication to a still more inconceivable extent. In examining, with a high magnifying power, Chalk or Whiting in a state of extremely minute division, two sets of particles may be distinctly seen ; one set having a crystalline structure, and the other presenting some indications of an organic aspect. If these be rendered more transparent by the use of Canada balsam, it is seen that they are polythalamous (many-chambered) shells of great minuteness ; some of them in fragments, and others nearly or quite perfect. The size of these varies from JT to -^L^ of a line ; and when, as in the Chalk of Southern Europe, they constitute nearly the whole mass, there must usually be above a million in every cubic inch. In the fourth part of a cubic line, or -J^- ot a grain, from 150 to 2UO can be ascertained to exist; and thus there would be from 1800 to 2400 in each grain, and far above ten millions in every pound of chalk. In the chalk of this country, and of other parts of the north of Euroj^p, there is a predominance of particles of a somewhat crystalline character ; but even these have in all probability once been combined in organic structures. In pursuing his researches on this subject, it occurred to Ehrenberg to examine the finer particles of calca- reous matter, which have been artificially separated from chalk, and are employed for various purposes. Of such, the glazing of the papers with which the walls of apartments are sometimes covered, and that of visiting cards, are partly composed ; and on scraping a little of this, and subjecting it to microscopic exami- nation, he was delighted to find the organic structure almost everywhere apparent. PORIFERA, OR SPONGE TRIBE. 559 CLASS III.— PORIFERA. 1224. When we examine the exterior of a piece of common Sponge, we observe that it is covered with minute orifices or pores (whence the name which has been given to the class), thickly set together ; and that larger openings are disposed at intervals amongst these. If these larger orifices, or vents, be traced into the substance, it will appear that they are the mouths of canals or vessels which ramify through it ; these have definite walls formed by the firm tissue of the sponge, but perforated with a large number of orifices, connecting them with the spaces that lie between their net-work of branches. The pores, on FIG. 729.— SPONGE. the other hand, open into a less regular arrangement of small tubes and cells, of which the spongy is principally composed. These spaces are produced by the in- terlacement of the fibres that form the solid framework ; they communicate with one another throughout the mass ; and the canals seem to take their origin from the midst of them, arising by small tubes which unite into larger ones, and these again meeting to form the wide channels which terminate in the vents. If, after making such an examination of the structure of the Sponge, we tear a small portion of it into fragments, its fibrous nature becomes very apparent. If we submit these fragments to a low magnifying power, it is perceived that they form a com- plete network, inosculating with each other in every direction. By applying a higher power, it is ascertained that they are of tubular structure. In the Common Sponge, the whole frame- work is composed of these tubular fibres, which in some parts are set very closely together, whilst in others they are loosely arranged. They consist entirely of an organic texture, rather approaching the horny substance of Animals (as is made evident by the smell emitted on burning it), than anything which we 560 STRUCTURE AND ACTIONS OF SPONGE. meet with in the Vegetahje Kingdom ; and it is to their elas- ticity that the Sponge owes those properties which make it so useful to. Man. 1225. In other forms of the group, however, spicula of earthy matter are disposed amongst these ; which add to the firmness of the structure, and diminish its elasticity, according to the amount in which they are present. These spicula are in some instances composed of carbonate of lime ; in others they consist of pure silex ; and their form varies according to the material. The earthy spicula are disposed at intervals through the whole mass ; but they are especially abundant in the neighbourhood of the canals, and around the external orifices, both of these and of the pores. In fact each of these orifices is strengthened by a regu- lar frame-work of spicula disposed around it, and in many in- stances the sharp ends of the spicula project from the surface ot the Sponge, as if for its defence. 1226. When Sponges are examined in their living state and natural condition, a constant and rapid stream of water is seen FIG. 730.— SECTION OP LIVING SPONGE. to issue from the larger orifices or vents. This stream is made apparent by the movement of the minute particles contained in it, and by the disturbance of those which may be floating in the surrounding fluid. On the other hand it is easily made apparent, that water is as constantly being imbibed through the minute pores ; and that, after traversing the smaller cavities of the NUTRITION AND GROWTH OF SPONGE. 561 spongy structure, it finds its way into the canals through which it is expelled. Some such absorption must take place, to supply the fluid incessantly discharged through the vents. According to an observation of Mr. Bowerbank's, since confirmed by Mr. Carter and other observers, the incessant passage of water through the channels of Sponges, is to be attributed to the action of cilia with which the cells lining the incurrent orifices are lined. 1227. The nutrition and growth of the Sponges appear to depend entirely, then, on the water which enters the pores, on the substances which it holds in solution, and on the minute particles suspended in it. From these and from the water itself, the animal tissue appears to derive the materials of its nourish- ment ; and the silicious and calcareous substances must be separated by it, from the state of solution in which they exist in the surrounding fluid. When the large quantity of this fluid which passes through the canals of the Sponge in a short time, is taken into consideration, it is not difficult to account for the derivation of these ingredients from it; although they often exist in such minute proportion, as scarcely to be recognised by the chemist. Not only does this circulation of fluid answer the purposes of nutrition, but it is subservient also to the process of excretion. On watching the currents of water that issue from the vents, it is observed that minute flocculent particles are incessantly detached and carried out by them ; these appear as if they were the residue of digestion, or pellicles excreted from the body and thrown off from the surface of the internal canals. Sometimes the vents are all on one side, whilst the absorbent pores are on the other ; and in one interesting species of a bottle-like form, the Grantia compressa, the pores are entirely situated on the outside, and the vents on the interior, so that a single constant and rapid current of fluid proceeds from the mouth, which is contracted into rather a narrow orifice. 1228. This movement of fluid through their tissue seems to be almost the only action that proves the existence of life in these simple beings. No obvious contraction can be perceived when they are touched or irritated. They may be punctured or 562 NUTRITION AND GROWTH OF SPONGE. cut with sharp instruments, pierced with red-hot wires, or torn into fragments ; and yet no change of form, or rather evidence of sensibility, can be perceived in them. The parts which are unimpaired will continue to present the same phenomena as be- fore ; and no injury seems to have any influence, beyond the por- tion immediately affected by it. Nevertheless some observers maintain that a shock, affecting the whole mass alike, does pro- duce an evident effect upon it. This has been particularly noticed in the Spongilla, or River-sponge. When allowed to fall into water from the height of a few inches, or when the stage of the miscroscope is struck, the tubular prolongations on which the vents are situated contract very sensibly, until the orifice is nearly closed, and projects but slightly. It has also been noticed that these projecting orifices vary considerably in their form at different times, even within short intervals, and when no external cause has influenced them. Some Naturalists state, moreover, that, although no sensible contractions and dilatations can be seen in the whole mass, a peculiar sensation is felt when the hand is placed upon a specimen still under water. This sensation is of a tingling character, and appears due to some movement in the individual particles of which the flesh of the Sponge is composed. 1229. The Sponges may be multiplied by artificial division 5 each portion then becoming a new individual, like the separated buds of Plants. But no such division appears to occur in their natural state ; and they are reproduced by the separation of minute spore-like bodies from the gelatinous portion of their tissue. This process takes place, in the species of our own coast, at the earlier part of winter. At that period, the little reproductive bodies, or gemmules, first appear as minute opaque yellow points, irregularly distributed in the substance of the body, and usually at a distance from the surface. As their development proceeds, they become larger and more opaque, and present a regular oval form. They then protrude from the gelatinous lining of the canals, into their cavity ; and it is seen that the protruding portion is covered with cilia, which are in active operation. After a further period, they become altogether EEPRODUCTION OF SPONGES 563 detached from the parent structure, and swim forth, by means of the cilia, through the large orifices in which the canals termi- nate. In this condition they appear as egg-shaped particles of gelatinous matter, the greater part of whose surface is covered with cilia ; but the smaller end, by which they were previously attached, is left bare. By the vibration of these cilia they swim about for some time, very much in the manner of Animalcules. Their motions are equal, smooth, and gliding ; and they appear to be influenced by each other's proximity. When they ap- proach near to each other, as is sometimes observed, they often arrest their course, and swim for a short time round each other. They appear by these movements to seek a place adapted to their development ; and to this they seem partly guided by the influence of light, which they seek to avoid. The nature of the site chosen varies with the species. Some incrust the surfaces of loose stones or shells ; others stand erect upon a solid base ; and others hang from the under surfaces of projecting rocks. Sometimes earthy spicula may be observed in the gemmules, before they have attached themselves ; and in those species which possess them in the perfect form, they always appear within a short time after they are fixed. No trace of internal canals, how- ever, can be discovered at this period; and the formation of these does not begin until after the gennnule has completely changed its condition. 1230. When it attaches itself to any surface, the gemmule adheres by its small extremity, and the cilia continue their action for some little time afterwards, as if to clear a proper site for the extension which is immediately to take place. The gemmule then spreads itself out into a flat transparent film ; and the earthy or horny fibres soon begin to appear in it. It then ex- hibits minute depressions on its surface, which gradually become deeper, so as to form canals penetrating into it; these unite with each other, and send out ramifications through the whole structure as it extends; and thus the spongy mass is at last fully formed. The spicula and fibres, which at first appeared to be confusedly developed in the gelatinous growing membrane, 564 FOSSIL REMAINS OF SPONGES. then manifest great symmetry and method in their distribution, with relation to the pores, canals, and vents. 1231. The Geographical distribution of the Porifera is very extensive; indeed it may be said to be almost universal. Every coast, from the Equator to the highest Polar regions, furnishes some kinds of Sponge ; but they exist in much greater abundance in warm latitudes than in cold, and they attain also a much greater size. They are all, of course, inhabitants of the water only, and if long removed from it they lose their vitality ; but there are many species which seem able to bear exposure to the air between the intervals of the tide, appearing to flourish equally well in deep water, or at a level which is occasionally left dry. 1232. There is some difficulty and uncertainty in regard to the Fossil remains of Sponges; but it is probable that these have come down to us from a very remote period of the earth's history, and it may be reasonably supposed that Sponges were among the earliest inhabitants of the ocean. These remains are found in two states, Sometimes the whole tissue has been per- meated by siiicious or calcareous matter ; so that, on the mass being broken, its internal structure is very evident. In other instances we have only the casts, which have been formed by the subsequent filling-up, with stony matter, of the cavities left by their decay. There is reason to believe that, in the Sponges of ancient date, the siiicious spicula must have predominated ; for we find their fossil remains almost always silicified, even in calcareous rocks. Thus, in the Chalk (in which they greatly abound) all the remains of Sponges present the character o£ flints. Some of these flints, when broken, exhibit very beautifully the structure of the Sponge ; and others possess only its external form. Now, many of the Chalk fossils are infiltrated with car- bonate of lime, and not with flint ; and this even when associated with Sponges. In the same flint-nodules which envelope Sponges, the shells of the Echinus (§ 1092) are found converted into crystallized carbonate of lime, and dense shells of Mollusca p FOSSIL REMAINS CF SPONGES. 565 are scarcely at all changed. It is evident, then, that some peculiar attraction for silicious matter exists in the Sponges ; and this is readily explained upon well-known chemical prin- ciples. If in a saturated solution of two salts, a crystal of one of those salts be placed, it will be increased by a crystalline deposit of its own composition ; whilst the other salt will not form any deposit around it. If two organic structures, there- fore,— one containing silicious spicula, and the other calcareous crystals, — be exposed to a fluid holding both these substances in solution, they will each attract from it their own ingredient. O LORD, HO^V MANIFOLD ARE THY WORKS ; TN WlsPOM HAET THOU MAbE THEM ALL." APPENDIX. ON THE INSTINCTS OF SOCIAL INSECTS. A GENERAL account has been elsewhere given (AniM. PHYSIOL., Chap. XIV.) of the habits and instincts of the Hive Bee ; and a similar sketch will be here given of the History of the Termites or White Ants, and of that of the Common Ants. The Termites, or White Ants, belong to the Order Neuroptera (§ 740) ; and are the only true social insects contained in that group. Next to the Locusts, they may be reckoned the most destructive Insects known to Man ; since not only articles of food, but clothing, fences, trees, and even houses, fall before their devouring jaws. As they are confined, with but few exceptions, to tropical climates, we are only acquainted with their ravages by the reports of travellers who have visited those regions ; but these reports are such as we may fully trust to, and even in France, one species has lately done a great deal of damage at Rochelle and other places. — The Termites live in immense com- munities, consisting of kings and queens, soldiers and labourers. The kings and queens are perfect insects, male and female ; and their office is solely to increase their kind. The soldiers appear to be the pupce, stopped in their development, so as never to possess wings or to acquire the reproductive organs ; it is their office to attack every object or living thing, that in anyway injures or endangers the safety of the nest ; and this duty they perform with the most reckless bravery, the labourers retiring within the nest during the time of danger. The labourers are probably to be regarded as the larvce, alike checked in their development ; their offices are manifold, — their duty being to take the eggs from the queen as fast as she lays them, to convey them to the nurseries and to tend them until hatched, and to feed the young, store provisions, build the nest, repair damages, and perform every kind of labour requisite for the good of the community. The nests of the Termites are so numerous all over the island of Bananas and the adjacent Continent of Africa, that it is scarcely 56S INSTINCTS OF TERMITES, OR WHITE ANTS. possible to stand upon any open place, such as a rice-plantation or other clear spot, where one or more of these buildings is not to be seen within fifty paces. In some parts near Senegal, as men- tioned by Adanson, their number, magnitude, and closeness of situation, make them appear like the villages of the natives. These buildings are usually termed " hills" from their outward appearance, which is that of little hills, generally pretty much in the form of sugar-loaves, and about ten or twelve feet in height. These hills continue quite bare until they are six or eight feet high ; but in time become, like the rest of the earth, almost covered with grass and other plants ; and in the dry season, when the herbage is burnt up by the rays of the sun, they somewhat resemble very large hay-cocks. The exterior of the building consists of one large shell or domed wall; which is large and NKSTS or TERMITKS The large nests, of which one is cut open vertical I}1 to show the interior, are those of the Termes bellicosut. The small nest (a) in the tree, is that of the Termes arborum / and at b is seen the arched gallery, by which it communicates with the ground. strong enough to shelter the interior from the weather, and to protect the inhabitants from the attacks of most of their enemies. It also serves to collect and preserve a regular degree of genial warmth and moisture ; which seems very necessary for hatching the eggs and cherishing the young ones. The interior is divided, with great regularity and contrivance, into a great number of INSTINCTS OP TERMITES, OR WHITE ANTS. 569 apartments ; some of which are intended for the residence of the kings and queens, and for the rearing of their numerous progeny ; whilst others serve as magazines, and are always found well filled with stores and provisions. These hills make their first appearance above ground, by a little turret or two, in the shape of sugar-loaves ; which only rise to the height of a foot, or a little more. Soon afterwards, at some little distance, while the former are increasing in height and size, the Termites raise others; and so go on increasing the number, and widening them at the base, till their works below are covered with these turrets, which they always raise the highest and largest in the middle ; they then, by filling-up the intervals between each turret, collect them, as it were, into one dome. They are not very curious or exact about these turrets, except in making them very solid and strong ; and when, by the junction of them, the dome is completed (for which purpose the turrets answer as scaffolds), they take away the middle ones entirely, except the tops, which, joined together, form the crown of the cupola ; and they apply the clay to the building of the works within, or to the erection of fresh turrets for the purpose of raising the hillock still higher. The royal chamber, so called on account ot its being adapted for, and occupied by, the queen, is situated near the centre of the hillock. It resembles the shape of an egg cut in half lengthways, and is at first not above an inch in length ; it is afterwards increased, however, to six or eight inches, or even more, in proportion to the size of the queen (§ 740). The floor and roof of this chamber ,are very solid, and are composed of hardened clay. Its walls are pierced by several entrances, which will admit the soldiers and labourers, but which are not large enough to allow the queen (who is, at full size, a thousand times the weight of a worker) to pass out. It is surrounded on all sides by a series of chambers, which may be called the royal apartments, and which are occupied by the soldiers and labourers that guard the queen, on whose safety depends the happiness, and probably even the existence, of the whole community. These apartments, being connected together by openings and passages, form an intricate labyrinth, which extends a foot or more in diameter from the royal chamber on every side ; and they are surrounded by the magazines and nurseries. The former are chambers of clay ; and are always well filled with a kind of provisions, which appear to consist of the gums or other thick juices of plants. The nurseries, which are so called because thej 570 INSTINCTS OP TERMITES, OB WHITE ANTS. always are found to contain eggs and young ones, are entirely composed of wooden materials, seemingly joined together with gums. These are placed as near as possible to the royal apart- ments. When the nest is in the infant state, they are close to the royal chamber ; but as, in process of time, the queen enlarges, it becomes necessary to enlarge this chamber for her accommo- dation ; and as she then lays a greater number of eggs, and requires a greater number of attendants, so is it necessary to enlarge and increase the number of the adjacent apartments ; for which purpose, the small nurseries that were at first built are taken to pieces, and are rebuilt a little farther off. The nurseries are inclosed in chambers of clay, like those which contain the provisions, but much larger. In the early state of the nest they are not larger than a hazel-nut ; but in old hills, they are often as large as the head of a child a year old. Under the dome is a large opeu space, which is surrounded by three or four large arches of a somewhat gothic form ; this space may perhaps be intended to equalise the temperature of the chambers below, by preventing either the sun or the cold air from at once affecting the latter. Beneath the lowest apartments are found a set of large passages, which communicate with all the chambers of the interior, and also with the galleries that diverge from the nest in various directions. These passages, which are thickly lined with the same kind of clay as that of which the hill is composed, ascend the inside of the shell in a spiral manner ; winding round the whole building up to the top, and intersecting each other at different heights, and communicating with the various chambers by galleries branching out from them. From the bottom of these are several large galleries, which lead downwards into the ground below, sometimes to the depth of three or four feet ; these are mines or quarries, whence the Termites obtain the fine gravel and clay, which they work up in their mouths to the consistence of mortar ; and then use in the construction of their buildings. Other galleries extend horizontally beneath the ground, at a small depth below its surface, to a great distance. Sometimes these passages cannot be continued under ground in the required direction ; and the Termites then make pipes or covered-ways along its surface, composed of the same materials with the nests. These they continue, with many windings and ramifications, for great lengths ; and they construct, where it is possible, subter- ranean pipes running parallel with them, into which they may sink and save themselves, if their galleries above ground are INSTINCTS OF TERMITES, OK WRITE ANTS. 571 destroyed by violence, or the tread of men or animals alarm tnem When a person accidentally enters any solitary grove, where the ground is pretty well covered with their arched galleries, they give the alarm by loud hissings, which :nay be distinctly heard at every step ; soon after this, their galleries may be searched in vain for the insects ; but little holes are found, just large enough to admit of their escape into the subterraneous roads. These galleries are of sufficient size to allow the Termites to pass and repass without stopping each other (though there are always numerous passengers), and to shelter them equally from light and air, as well as from their enemies, — of which the Ants, being the most numerous, are the most formidable. If the Termites are dislodged from their covered ways, the various species of Ants (which are probably as numerous above ground as the Termites are in their subterranean passages) instantly seize and drag them away to their nests, to feed their young brood. The Termites are, therefore, exceedingly solicitous about preserving their covered ways in good repair ; and if one of these be de- molished for a few inches in length, it is wonderful how soon they will rebuild it. At first, in their hurry, they run into the open part an inch or two, but stop so suddenly that it is evident they are surprised ; for though some will run straight on, and get under the further part of the arch as speedily as possible, most of them run back as fast, and very few will venture through that part of the gallery which is left uncovered. In a few minutes they may be seen engaged in rebuilding the arch ; and even if three or four yards of their gallery have been destroyed, it will be restored by the next morning, and will be found to contain numerous Termites passing a*long in both directions. If the gallery be several times destroyed, they will at length seem to give up the point, and build another in a different direction ; but if the old one led to some favourite plunder, they will rebuild it again in a few days ; and unless the nest be destroyed, they will never totally abandon their gallery. The galleries of the Termites are often carried beneath the foundations of houses and store-houses, at several feet below the surface : sometimes they rise through the floors ; but they are frequently continued in the interior of the posts of which the sides of the buildings are composed, following the course of the fibres to the top, and having lateral perforations or cavities here and there. While some of the Termites are employed in gutting the posts, others ascend from them, entering a rafter or some other part of the roof, in search (as it would seem) of thatcti, 572 INSTINCTS OF TERMITES, AND OF ANTS. which is their favourite food. If they find it, they bring up wet clay, and build galleries through the roof in various directions, as long as it will support them. In this manner a wooden house is speedily destroyed ; and all that it contains is, at the same time, subjected to the ravages of these destructive insects. In carrying on this business, they sometimes appear to find, by some means or other, that the post has a certain weight to support, and then, if it is a convenient track to the roof, or is itself a kind of wood agreeable to them, they bring their mortar ; and, as fast as they take away the wood, replace the vacancy with that material, which they work together more closely and compactly than human strength or art could ram it. Hence, when the house is pulled to pieces, the posts formed of the softer kinds of wood are often found reduced almost to a shell ; and almost all of them are transformed from wood to clay, as solid and hard as many kinds of free-stone used for building in England. Of the true Ants, which belong to the Order Hymenoptera, a general description has been already given (§ 760) ; but it re- mains to notice some of the chief points in the structure of their habitation, and in their social economy. As among the Termites, there are four orders in the community,— the perfect males and females, the workers, and the soldiers ; the workers and soldiers, however, cannot be regarded as either larvae or pupae, since they undergo the regular metamorphoses ; but they have neither tho wings nor the reproductive organs developed. As among the other social Hymenoptera, they are neuters, that is, of no sex ; but they most nearly approach the female. The soldiers of the Red Ants of this country are nearly three times the size of the workers, and their heads are larger in proportion ; those of the Yellow Ant are about twice the. size of the workers. In describing the habitations of this race, it will be best to confine ourselves to the latter of these species, which is very abundant in our own country. Their hillocks are apparently made in a much less elaborate manner than the dwellings of the Termites; but they are not less perfectly adapted to their required object. They are composed of bits of stubble, fragments of leaves, small stones, splinters of wood, &c., which are collected by the Ants, and laid (as it might appear) promiscuously together ; but although apparently a careless heap, the hillock is really a most ingenious device for evading the effects of wind and the attacks of enemies, and yet more especially for receiving and husbanding the heat of the sun. Its exterior always presents the appearance of a dome ; HABITATIONS OF ANTS. 573 and from its summit a number of avenues, carefully excavated like tunnels, lead downwards into the interior, — the number of them depending on the population and extent of the nest. Their external apertures are of varied size ; there is sometimes a prin- cipal one at the top ; but there are usually several, of unequal size, which are surrounded by passages arranged with great regularity. In the habitations of many species of Ants, we never find an aperture of sufficient size to allow the entrance of enemies or the passage of rain-water ; the dome being closed on every side, and having only one aperture near the base, which is not unfrequently continued into a serpentine gallery many feet in extent. With the Yellow Ants, however, it is quite different. They stand in crowds on their nests during the day, and seem quite fearless of any disturbance to the interior ; and at night, before retiring to the bottom of their habitation, they close all the apertures with the greatest care. This curious fact was first discovered by Huber, to whom we owe so much of our knowledge of the economy of Bees and Ants. On closely watching the appearance of one of these nests, he found it undergoing an hourly change ; so that the apertures, so spacious in the middle of the day, gradually diminished in size towards the evening, and at night entirely disappeared ; the dome being then closed in every part, and all the Ants being concealed within. In order to accomplish this, the Ants draw little bits of wood into the openings, placing them across the entrance, and sinking the ends in the covering of the hill ; they then fetch others, laying them across the first, and so continue selecting other pieces, smaller and smaller as the work advances towards its accomplishment ; and finally close the opening with bits of dried leaves, and similar materials. — In the morning, a few Ants may be seen wandering about the exterior of the nest, — the numbers gradually increasing, as others emerge from the interior under the little roofs formed at the entrance of each avenue ; and these soon set to work, and begin to clear away the barricades. This employment continues for hours, until at length the apertures are sufficiently extended ; and the materials used in closing them are distributed over the exterior of the nest. This is a daily labour, unless it rains, or the morning threatens rain ; and if rain come on after it has been performed, they hasten to close the apertures as at night. The dome contains a number of spacious chambers, communi- cating with each other by galleries ; these chambers, however, are low, irregular in figure, and carelessly constructed ; but they are convenient, nevertheless, for the purpose for which they are VOL. II. R R 574 INSTINCTS OF ANTS. constructed, — that of containing the larvae and pupse at certain hours of the day. The eggs, when deposited by the female or queen ant (who drops them at random in her progress through the nest), are taken charge of by the workers ; who immediately seize them and carry them in their mouths, in small parcels, and lay them in heaps in separate apartments. They constantly tend them until they are hatched, incessantly turning them back- wards and forwards with their tongues for the purpose of mois- tening them, without which they would come to nothing ; and it must be to the moisture thus imparted to them, that the great enlargement of the eggs is due, which has been constantly noticed previously to the hatching of the larvae. The workers frequently remove the eggs from one quarter of the nest to another, as they require a warmer or a cooler, a moister or a drier atmosphere ; and at intervals they brood over them, as if to impart to them a genial warmth. When the larvae come forth, the workers are almost constantly engaged in supplying their wants and forward- ing their growth. Every evening, an hour before sunset, they regularly remove the whole brood (as well as the eggs and pupae) to cells situated lower down in the earth, where they will be safe from cold ; and in the morning they as constantly remove them again towards the surface of the nest, — unless there is a prospect of cold or wet weather, in which case they do not remove them. When the rays of the sun first strike upon the nest, a most ani- mated scene takes place. The Ants on the exterior are the first to feel the influence of the warmth ; they enter the nest, run along the avenues and galleries to the various chambers, and communicate the intelligence to every ant they meet, — tapping their fellows gently with their antennae, or, if this be not attended to, biting them severely with their mandibles. At last the whole colony seems to partake of the excitement, and each labourer then carefully takes a larva or a pupa in his mouth, conveys it through all the winding passages to the outside, and places it in such a position as to receive the rays of the sun. The larvae and pupae are seldom exposed to the full rays of the sun for a longer period than fifteen or twenty minutes ; they are then conveyed into little cells constructed on the exterior of the nest purposely to receive them, aud are protected from the too great heat of the sun's rays, by a slight covering of chaff, stubble, or other light matter. As the heat of the sun decreases in the afternoon, the larvae and pupse are again fully exposed to it for a short season as before, and are then carefully returned one by one, through the almost interminable passages, each into the identical chamber INSTINCTS OP ANTS. 575 from which it was brought in the morning; and after this they are carefully fed by the workers, who nourish them with the food they have collected during the day. When the larvoa have attained their full growth, they spin a cocoon, in which they remain as pupae until the time of their final change. In this state they are commonly, but erroneously, known under the name of " eggs;" and being a favourite article of food with pheasants and partridges, they are eagerly sought after by persons who rear these birds from the egg. The cocoons containing the pupae are of a long cylindrical form, and of a dirt^r white colour ; and the contained animals are perfectly motionless. When ready to come forth as perfect Ants, they cannot, like most other Insects, set themselves free from their envelope ; but they are dependent upon the assistance of the workers, who moisten it and cut it with their mandibles, and then gently draw forth the contained body. The greatest care is bestowed upon the winged Ants, — the perfect males and females, — on which the continuance of the race depends ; these are most assiduously tended by the workers, who cleanse their bodies, extend their wings, supply them with food, and accompany them in their wanderings through the hive. A large number of the winged Ants are produced every season in each community; and they may be frequently seen in the autumn, covering almost the whole surface of the hillock. The greater number of these, however, perish in various ways ; and only a small number remain, either to found new colonies, or to keep up the population of the parental resi- dence. Sometimes the new colony is commenced by the queen alone : who excavates her future dwelling-place, and lays the eggs, feeds the larvae, and tends the pupaa, without any assist- ance ; but the workers that are first produced, then aid her in the requisite attentions to the subsequent progeny. In other instances, the queen falls in with a few workers, that have wan- dered, at this period of excitement, to an unusual distance from the nest ; and if so, they unite their labours with hers. The most remarkable fact connected with the history of Ants, is the propensity possessed by certain species to kidnap the workers of other species, and to compel them to labour for the benefit of the community, thus using them completely as slaves ; and, as far as we yet know, the kidnappers are red or pale- coloured Ants, whilst the slaves are of a jet black. The time for capturing slaves extends over a period of about ten weeks, and never commences until the male and female Ants are about coming forth from the pupa state ; and thus the marauders nevei 576 INSTINCTS OF ANTS. interfere with the continuation of the species. This appears to be a special adaptation of their peculiar instinct ; for if the attacka were made on the nests of the Negro Ants, before those by whom the race is propagated are ready to issue forth, it must speedily become extinct. — When the Red Ants are about to sally fortli on a marauding expedition, they send scouts to ascertain the exact position in which a colony of Negro Ants may be found ; these scouts, having discovered the object of their search, return to their nest and report their success. Shortly afterwards, the army of Red Ants marches forth, headed by a vanguard, con- sisting of eight or ten Ants only, which is perpetually being changed, — the individuals which constitute it, halting, when they have advanced a little before the main body, falling to the rear, and being replaced by others. When they have arrived near the Negro colony, they disperse, wandering through the herbage, and hunting about, as if aware of the neighbourhood .of the object of their search, yet ignorant of its exact position. At last they discover the settlement ; and the foremost of the invaders rush- ing impetuously to the attack, are met, grappled with, and frequently killed by the Negroes on guard. The alarm is quickly communicated to the interior of the nest ; the Negroes sally forth by thousands; and the Red Ants rushing to the rescue, a desperate conflict ensues, which, .however, always terminates in the defeat of the Negroes, who retire to the innermost recesses of their habitation. Now follows the scene of pillage. The Red Ants, with their powerful mandibles, tear open the sides of the Negro Ant-hill, and rush into the heart of the citadel. In a few minutes each of the invaders emerges, carrying in its mouth the pupa of a worker Negro j which it hai obtained in spite of the vigilance and valour of its natural guardians. The Red Ants return in perfect order to their nest, bearing with them their living burthens. On reaching the nest, the pupaa appear to be treated precisely as their own ; and the workers, when they emerge, perform the various duties of the community with the greatest energy and apparent good-will ; they repair the nest, excavate passages, collect food, feed the larvse, take the pupae into the sunshine, and perform every office which the welfare of the colony seems to require ; in fact, they conduct themselves entirely as if fulfilling their original des- tination.* * The details of this Appendix have been chiefly taken from Mr. Newman'e very excellent " Familiar Introduction to the History of Insects." INDEX. N. B.—The numbers refer to the paragraphs. A. Alpine Swift, 408. Antelopida, 264. Amblyrhynchus, 494. Anthracidce, 796. AARD-WOLF, 194. Ameividce, 499. Antipathes, 1159. Aard-vark, 249. American Bison, 270. Ant-Lion, 742. Abdominalia, 895, 898. American Ostrich, 439. Anura, 526. Aberdevine, 387. Arniida;, 600. Apes, 148. Acalephce, 1182. Ammocaetes, 640. Aphaniptera, 800. Acanthocephala, 923. Acanthocinus, 717. Ammodytida\ 629. Ammonite, 969. Aphides, 785. Aphis, 785. Acanthopteri, 607. Ammonitida>, 969. Aphis-Lion, 743. Acanthopterygii, 571. Amoeba, 1220. Aphroditidce, 910. Acarina, 833, 838. Ampelidce, 398, 404. Aphrophora, 784. Acarus domesticus, 839. Amphinomidw, 910. Apidce, 764. Acasta, 897. Amphioxus, 642. Aplysiadee, 1003. Accentor, 400. Achatina, 982. Amphipneusta, 532. Amphipoda, 868. Apoda (Batr.), 533. Apoda (Cirrh.), 89.1, 898. Acherontia, 773. Amphisbnceidce., 503. Aporrhais, 993. Achetidce, 730. Acipenseridce, 596. Amphisyle, 607. Amphitrite, 912. Apteryx, 441. Apus, 877. Acorn-shell. 897. Amphiumidce, 531. Arabian Camel, 278. Actinia, 1122. Ampullaria, 994. ARACHNIDA, 809. Actinophrys, 1220. Anabas, 619. Araneida, 824. Aculeate, 752. Anabatidce, 619. Araneiformia, 857, 899. Adamsia, 1124. Anableps, 632. Arcacece, 1034. Addax, 268. Anacanthini, 627. Archer-fish, 613. Adder, 512. Anarrhicas, 621. Arctic fox, 193. Adelarthrosomata, 834. Anastoma, 982. Ardeidce, 448. Adjutant-Stork, 449. Anatidce, 454. Arenicolidce, 910. j&olida>, 1006. Anchovy, 635. Argala,449. JEolis, 1006. Ancylus, 983. Argali, 274. JEpyornis, 442. Andrenidce, 763. Argonautidte, 962. Agamidce, 496. Angel Fish, 585. Argyroneta, 830. Agaricia, 1138. Anglers, 623. Argulus, 888. Agouti, 234. Angora Goat, 272. Argus Pheasant, 432. Agrion virgo, 737. Anguine Lizard, 501. Armadillo, 247. Ai, 241. Anguis, 502. Armadillo pustulatus, 873, Ailurus, 199. Anilocra, 873. Arnee, 271. Albatross, 459. Anisodactyla, 285, 286. Artemia, 878. AlcedinidtK, 412. ANNELIDA, 905. ARTICULATA, 650. Alciria*, 457. Anobium, 712. Arvicolte, 228. Alcippe, 896. Anodon, 1033. Asaphus, 874. Alcyonian Polypes, 1150. Anolis, 495. Ascaris, 923. Alcyonidium, 1078. Anomia, 1024. Ascidice, 1061. Alcyoniura, 1153. Anomoura, 861. Asilidce, 796. Alligator, 488. Anoplotherium, 298. Asiphonata, 1020, 1021. Alligator-tortoise, 484. Anoplura, 801. Asp, 512. Alpaca, 282. Alpine Partridge, 433. Ant, 760, App. Ant-eaters, 250. Aspergillum, 1046. Ass, 301. 578 INDEX. . B, — The numbers refer to the paragraphs. Asterias, 1103. Bembecidie, 759. Brown-Gannet, 461. Asteroida, 1120, 1149. Beridai, 794. Brown-Ptarmigan, 4M. Astraea, 1137. BeroS, 1192. Brown-Rat, 223. Ateles, 159. Bicelluli, 788. Brush Turkey, 436. Athalia, 753. Bimana, 127. Bryozoa, 1070. Athericera, 797. Bird-lice, 802. Buccinidce, 989. Atlantidce, 1009. BIRDS, 322. Buccinum, 989. Atropos, 741. Birds of Paradise, 396. Buceridat, 397. Auk, 457. Birgus, 861. Buffalo, 270, 271. Aulostomidce, 607. Bison. 270. Bufonidte, 528. Auriculidce, 983. Bittern, 448. Bugs, 787. Aurochs, 270. Black Bear, 199. Bulimus, 982. Australian bower-bird, 395. Blackbird, 402. Bulla, 1003. Avicula, 1026. Black-cap, 400. Bullaea, 1003. Avocet, 451. Black-Cock, 433. Bulldog bat, 172. Axolotl, 532. Black-Coral, 1159. Bullfinch, 388. Aye-aye, 164. Black Rat, 223. Bullhead, 608. Black-Scoter, 455. Bullidv, 1003. Black Swift, 408. Buprestis, 712. B. Blaps mortisaga, 713. Burbot, 627. Blattidce, 727. Burrowing Owl, 888. Baboon, 154. Blatta orientalis, 727. Bursatella, 1003. Babyroussa, 297. Bleak, 631*. Burying Beetle, 707. Bacillarice, 1218. Blennidce, 621. Bush-Antelope, 266. Bacteria fragilis, 729. Blepharis, 616. Bush-Goat, 266. Bactrian Camel, 278. Blind-Worm, 502. Bustard, 444. Baculite, 970. Blue Shark, 588. Butcher-birds, 398. Badger, 198. Boar, 297. Butterflies, 772. Balajna, 214. Boat-Bill, 448. Buzzard, 373. Balcunidce, 214. Boat-Flies, 789. Byrrhidee, 708. Balaenoptera, 214. Bocydium, 784. Balanidce, 897. Bohemian Chatterer, 404. Balaninus, 715. Boidce, 507. C. Balanus, 897. Bombardier Beetle, 702. Bald Erne, 370. Bombi, 765. Caaing Whale, 211. Bald-Pike, 600. Bombyliidce, 796. Cachalot, 213. Balistes, 605. Bombycidce, 776. Caddice-fly, 747. Balistidee, 605. Bombyx Mori, 684. Cfcciliadce, 533. Bandicoot, 311. Bonito, 614. Calamarv, 964. Bank Swallow, 407. Bonnet-Limpet, 999. Calandra, 715. Bankive Jungle Fowl, 432. Bony-Pike, 598. Caligus, 889. Banxring, 179. Booby, 461. Callichroma, 717. Barbary Ape, 155. Book-lice, 741. Calling Crabs, 860. Barbel, 631*. Book-Scorpion, 837. Callithrix, 160. Barnacles, 896. Bopyrus, 872. Calymene, 874. Barnacle Goose, 455. Boreus, 745. Calyptraidce, 999. Barracuda, 613. Bot-Flies, 799. Camberwell Beauty, 772. Basilisk, 495. Bothriocephalus, 926. Camel, 278. Basking Shark, 587. Bassaris, 195. Botryllidce, 1063. Bottle-headed Whale, 212. Camelidte, 278. Camelopardidce, 263. Basse, 609. Bovidcp, 269. Canada Goose, 455. Bat, 165. Boviform Antelopes, 268. Canary, 388. Bat-louse, 791. Bowerbankia, 1071, 1078. Cancer, 859. BATRACHIA, 515. Bower-bird, 395. Canidce, 192. Bdellidcc, 840. Box Tortoise, 484. Cantharis, 714. Bear, 199. Brachinus, 702. Cape Hunting-Dog, 193. Bear Animalcule, 841. BRACHIOPODA, 1048. Cape Mole, 176. Beaver, 229. Beche-de-mer, 1115. Brachelytra, 705. Brachmin Ox, 269. Capercailzie, 433. Caprella, 870. Bed-Bug, 788. Bee, 762. Brachyoura, 859. Brachyurus, 160. Caprida?, 272. Capriform Antelopee, 267. Bee-Bird, 773. Bradypus, 240. Caprimulgidce, 406. Bee-eater, 413. Branchiopoda, 857. Capromys, 227. Beetle-mite, 839. Bream, 631*. Capuchins, 159. Beetles, 696. Brent-Goose, 455. Capybara, 234. Belemnite, 965. Brill, 628. Car ab idee, 701. Bellows-fish, 607. Brown-Bear, 199. Caracaras, 373. Beluga, 211, 598. Brown-Creeper, 419. Carcharidce, 588. INDEX. jtf.B. — The numbers refer to the paragraphs. 579 Carcinus, 859. Chevrotain, 277. Colossochelys, 486. Cardiacece, 1037. Chigoe, 800. Coluhridce, 500. Cardisoma, 860. Chiloynatha, 808. Colubrine Snakes, 506. Cardium, 1038. Chilopoda, 807. Colugo, 163. Carinaria, 1008. Cbimaera, 590. Columbidce, 428. Carnivora, 181. Chimceridcc, 590. Coli/mbidcc, 456. Carp, 631*. Chimpanzee, 148. Comatula, 1108. Carpenter Bee, 764. Chinchilla, 235. Common Fowl, 432. Cartilaginous Fishes, 571. ChinchillidcK, 235. Conchoderma, 896. Caryophyllea, 1135. Chinese Umbrella, 1004. Condor. 378. Cashmir Goat, 272. Chionidce, 434. Condylura, 176. CassididcB, 718. Chirocephalus, 878. Conger, 637. Cassis, 990. Chironomus, 793. Con idee, 987. Cassowary, 440. Chirotes, 503. Conirostres, 386. Castoridee, 229. Chiroteuthis, 964. Cony, 294. Cat tribe, 186. Chiton, 1000. Conus, 987. Catodontidce, 213. Chlamydosaurus, 496. Coot, 452. Caviare, 596. Chlamyphorus, 248. Copepoda, 885. Cavidai, 233. Chondroyrada, 1195. Coral Islands and B-eefr, Cayman, 488. Chough, 394. 1140 Cebidce -158. Chromidte, 625. Corallium, 1159. Cebus, 159. ' Chrysididcc, 757. Careodea, 788. Cecidomvia, 793. Chrysochloris, 176. Cormorant, 461. Cellulicolce, 825. ChrysomelidcK, 719. Coronula, 897. Centipede, 807. Chub, 631*. Corvidcv, 393. Cephalaspis, 644. Cicada, 782. Coryphwnidce, 617. CEPHALOPODA, 949. Cicadidcc, 782. Coryphium, 869. Cephalopteridce, 582. Cicindelidce, 701. Cossus, 775. Cepolidce, 618. Cidaris, 1102. Cottus, 608. Cerastes, 512. Cimex, 788. Couendou, 232. Cercarise, 924. Cimicidce, 788. Cowcow, 425. Cercoleptidcc, 185, 200. Cinereous Erne, 370. Cowry, 986. C'er cop idee, 784. Cercopithecus, 153. Cirrigrada, 1195. Cirrhobranchiata, 1001. Coypii, 230. Crab, 859. Cercyon, 706. Cirrhopoda, 857, 891. Crab-eating Opposum, 809, Cerithiidw, 993. Civet, 195. Crabronidce, 759. Certhiadcp, 419. Cladocera, 879. Cracidce, 431. Cervidee, 260. Clam, 1036. Crake, 452. Cestoidea, 925. Clavagella, 1046. Crane, 447. Cestracion, 646. Clavellinidce, 1062. Craniidcc, 1051. Cestrnciontidce, 587. Clepsine, 919. Cray-fish, 8G2. Cestum Veneris, 1193. Clio, 1012. Creeper, 419. Ceiacea, 207. Clothes'-Moth, 778. Crested Curassow, 481. Cetonia, 710. Clotho, 828. Crested Heron, 448. Chaetodon, 613. Clupeidce, 635. Ci'epuscularia, 773. Chcetodontida!, 613. Clypeaster, 1102. Cricket, 730. Chalcidce, 501. Coati, 199. Crinoidea, 1108. Chalcididcp, 757. Coal-fish, 627. Crioceratite, 970. Chamacece, 1035. Cobbler-fish, 616. Crioceridce, 720. Chameleonidce, 492. Cobra di Capello, 510« Cristatella, 1079. Chamois, 264, 267. Coccidce, 786. Crocodile, 488. Char, 634. Coccinella, 721. Crossbill, 390. Characinidcc, 632. Coccus, 786. Crotafidce, 513. Charadriadcc, 445. Cochineal, 786. Crow, 393, 394. Chatterers, 404. Cock of the Woods, 433. CRUSTACKA, 842. Cheese-Hopper, 798. Cockatoo, 422. Cryptophialus, 898. Cheetah, 188. Cockchafer, 710. Ctenoidians, 64S. Cheiromeles, 172. Cockle, 1037. Ctenophora, 1191. Cheiromys, 164. Cockroach, 727. Cuckoo, 425. Cheironectes (Mam.), 309. Cocosteus, 644. Cuckoo-spit, 784. Cheironectes (Fish), 623. Cod, 627. Cuculidcv, 425. Cheiroptera, 165. Codling-Moth, 777. Culicidcc, 753. Chelifer, 837. Ccelioxys, 764. Curassow, 431. Chelmon, 613. Camomyidie, 794. Curculio, 715. Chelonia, 483. Coanurus, 926. Curlew, 450. Cnelonidce, 485. Coleoptera, 696. Cursores (Birds), 437. Chelydidce, 484. Cbelydra, 484. Colidce, 391. Colobus, 152. Cursores (Spiders), 826. Cursoria (Insects), 726. 580 INDEX. N.B.—The numbers refer to the paragraphs. Curucui, 411. Diurnal (Lepidoptera), 771. Emysaurus, 487. Cushat, 428. Dodo, 429. Enaliosauria, 489. Cuttle-Fish, 964. Dog, 13, 14, 193. Encrinus, 1111. Cyamus, 870. Dog-fish, 589. Entellus, 151. Cycloidians, 643. Dolomedes, 826. Entomophaga, 755. dyclobranchiata, 1000. Dolphin, 211. Entomostraca, 857, 876. Cyclops, 885. Donax, 1039. ENTOZOA, 92C. Cyclopterus, 622. Dor, 710. Epeira, 829. Cyclostomi, 639. Dorado, 617. EphemerldcE, 738. Cyclostomidce, 983. Dorcus, 711. Epimachus, 396, 418. Cjdippe, 1191. Doridce, 1006. Epizoa, 890. Cynipidce, 755. Doris, 1006. Equidce, 299. Cynocephalus, 156. Dormouse, 221. Erinaceadfe, 178. Cynthia, 1062. Dorsibranchiata, 909. Eristalis, 797. Cypraidce, 986. Dory, 616. Erne, 370. Cyprinidce, 631*. Dotterel, 445. Errantes, 828. Cypris, 883. Douroucouli, 160. Eryx, 507. Cvsticercus, 925. Draco, 497. Eschara, 1078. Cytherea, 1039. Dragon-flies, 737. Esculent Swallow, 409. Cytherina, 883. Dreissena, 1031. Esocidce, 633. Drill, 156. Euglena, 1215. Dromedary, 278, 281. Eunicidv, 910. D. Dromiidce, 861. Euphrosyne, 910. Drone-fly, 797. European Bison, 270. Dab, 628. Drummer, 727. European Hoopoe, 418. Dace, 631*. Duck, 455. European Nuthatch, 419. Dactylopterus, 608. Duck-billed Platypus, 317. European Wren, 420. Daman, 294. Dugong, 305. Euryale, 1107. Daphnia, 879. Dunnock, 400. Exocoetus, 626. Darter, 461. Dynastes, 710. Day-flies, 738. Dysopus, 172. Darwin's Rhea, 439. Dyticus, 703. F. Darwin's theory of Coral Dzigguetai, 301. formations, 1143. Falconidcp, 365. Dasyurus, 310. Fallow-Deer, 261. Dead-man's-hand, 1155. E. Felida*, 186. Death's-head Moth, 773. Fer-de-Lance, 514. Death-watch, 712. Eagle, 369. Ferret, 196. Decapoda, 858. Eagle-Owl, 382. Field-Cricket, 730. Deer. 260. Eagle-Ray, 582. Field-Mouse, 226, 228. Delphinidce, 210, 211. Eared Owls, 382. Fifteen-spined Stickleback, Demoiselle, 447. Ear-shell, 999. 608. Dendrolagus, 313. Earthworm, 914. Filaria, 923. Dendrophyllia, 1136. Earwig, 725. File-Fish. 605. fientaliidte, 1001. Echidna, 320. Filiformia, 870. Dentirostres, 398. Echinida, 1092. Filitelce, 828. Desman, 177. Echinococcus, 926. Finches, 386, 387. Dermaptera, 725. ECHIXODERMATA, 1089, 1090. Fin-headed Ray, 582. Dermestes, 707. Echinorhynchus, 923. Fin-pike, 599. Desmodus, 170. Echinus, 1102. Firolidcv, 1008. Diamond Beetle, 715. Edentata, 239. FISHES, 535. Dintomacea?, 1218. Dibranchiala, 958. Edriophthalma, 857, 868. Edwardsia, 1124. Fishing-Frog, 623. Flssipenn, 582. Lvcaon pictus, 193. Melecta, 764. M'ylodon, 244. Lycosa, 826. Melidcc, 185, 198. Myopotamus, 230. Lyqa-odea, 788. Meliphaqidfc, 417. MYHIAPODA, 804. Lvnx, 191. Lyretail, 420. Me.llifera, 762. Meloe, 714. Myrmecophaga, 250. Myrmeleonidae) 742. Melolontha, 710. Mysis, 864. Meropidce, 413. Mi/tilacea>, 1030. M. Merlin, 367. Myxinidte, 641. Merganser, 455. Macacus, 154, 155. Midge, 793. Maccaw, 422. Miliola, 1222. N. Macliilis, 803. Millepede, 808. Mackerel, 614. Mimic Beetles, 708. Nais, 917. Macrobiotidce, 841. Minnow, 631*. Naja, 510. Macrogiossa, 773. Mite, 838. Nandu, 439. Macropodida?, 312. Mitred Basilisk, 495. Napu, 277. Macroscelis, 177. Moa, 442. Narwhal, 212. Macroura, 862. Mocking-Bird, 402. Natanten, 830. Mactra, 1039. Mole, 175. Natatores, 453. Madrepore, 1136. Mole-Cricket, 730. Naticidce, 998. Maenura, 420. Mole-Uat, 227. Aautilid(V, 968. Magilus, 995. MOLLUSCA, 934. Nautilites, 968. Magot, 155. Moloch, 496. Nautilus pompilius, 966. Magpie, 394. Monad, 1216. Necrophaga, 707. Magpie-moth, 777. Monitor, 498, 499. Necrophorus, 707. Maia, 859. Monkey, 150. Nematelmia, 922, 923. Maigre, 612. Monk-fish, 585. JVematoidea,92Z. Malacobdella, 919. Monoculus, '879. Nemertidee, 924. Malacopterygii, 571. Monodon, 212. Nemestrina, 796. Malapterurus, 631. Monomera, 786. Nemocera, 792, 793. Mallard, 455. Monomervtomata, 833. Nemoptera, 745. Malleus, 1028. Monotremata, 317. JVepida-, 789. Mallophaga, 802. Moon-fish, 604. Nepjtune's cup, 1155. Malmag, 162. Moor-Harrier, 374. Nereulee, 910. Malmignatte, 829. Moor-Hen, 452. NeritHa-, 996. MAMMALIA, 71. Moose-Deer, 260. Neritina, 996. Mammoth, 288. More- Pork Bird. 406. Aeuroptera, 735. Man-of-war Bird, 461. Mormyridee, 633. Newt, 531. Manatidce, 305. Morse, 203. Nig-ger, 753. Mandrill, 156. MoschidtB, 276. Night-Hawk, 406. Mango-fish, 609. Mosasaurus, 498. Nightingale, 399. Manis, 250. Mosquito, 793. Mtitelce, 828. Mantidce, 723. Moths, 773. Noctilionidce, 168, 172. Mantis, 728. MantispidcE, 746. Mother Careys Chicken,459. Moufflon, 274. Noctiluca, 1185. JVoctuidte, 777. Murgaritacece, 1026. Mouse, 226, 228. Noctule, 171. Marmot, 220. Muqilidce, 620. Nocturnal Lepifoptera,; Marmozet, 160 f Mullet, 620. 774. Marsh Sandpiper, 450. Mullldoa, 611. Nomad a, 764. Marsh Tortoises, 484. MurrKnid(K, 637. Wotacantha, 792, 794. Marsupialia, 309. Murex, 991. Notacanthida:, 618. Alarten, 196. Muricidce, 991. Norway Haddock, 608. Martin, 407. Muridce, 223. Notidanidte, 587. Mason Bee, 764. Mastodon, 289. Muscicapidw, 403. Muscida:, 798. Notonectidcr, 789. Nudibranchiata, 1005. May-fly, 744. Musk-Beetle, 717. Numidian Crane, 447. May-worm, 714. Musk-Deer, 276,277. Nummulite, 1222. Meal-worm, 713. Musk-Ox, 271. Nuthatch, 419. Meandrina, 1137. Musk-Rat, 177, 228. Nut- Weevil, 715. Medusa, 1186. Muskquash, 228. IVycteribiidee, 791. Megaderm, 169. Miuafkagidm, 392. Nycterin, 169. Megalicthys, 645. Mussel, 1030. Nyctipithecus, 160. Megalonyx, 245. Mustelid6. Snapping-Turtle, 485. Stormy Petrel, 459. Sea-Pike, 626. Snipe, 450. Stratiomidte, 794. Sea- Rush, 1156. Snow-Bunting', 388. Strepsiptera, 722. Sea-Snipe, 607. Snow-Flake, 388. Sfrigida*, 380. Sea-Swallow, 460. Snow-Goose, 455. Striped Tunny, 614. Sea-Unicorn, 212. Snowy Owl, 3S3. Strombidcr, 992. Sea-Urchin, 1092. Solan Goose, 461. Strongylus, 923. Sea-Wolf, 621. Sole, 628. Struihionida?, 438. Seal, 201. Solen, 1040. Sturgeon, 596. Sebastes, 608. Solidunqula, 285, 299. Sturiones, 572. Secretary Falcon, 375. Solitaire, 429. Sturnida>, 395. Securifera, 753. Sedentary Spiders, 829. Selachii, 375. Solitary Snipe, 450. Solpuyidcc, 835. Sorex, 177. Stvlops, 722. Sucking-Fish, 622. Snctoria, 918. Semiplantigrade Carnivo- Soricida;, 177. Sugar Louse, 803. ra, 185. Spalax, 227. Suidcc, 295. Semnopithecus, 151. Sparidce, 612. Suleah-fish, 609. Sepiidcc, 964. Sparrow, 387. Sun-Bird, 416. Serpents, 505. Sparrow-Hawk, 371. Sun-Fish, 587, 604. Serricornia, 712. Spatangus, 1102. Surgeon-fish, 618. Sertularian Polypes, 1177. Spatularidw, 597. Surinam Toad, 529. Serpula, Oil. Spectacled Snake, 510. Surmullet, 611. Sesnlia, 897. Spectre-Insects, 729. Swallow, 407. Shad, 635. Spermaceti Whale, 213. Swallow-tailed Moth, 777. Shark, 585. Sphaeridium, 706. Swan, 455. Shark Rav, 584. Sphargis, 485, Swift, 408. Sheath-bills, 434. Sphegidce, 759. Sword-Fish, 615. Sheep, 274. Sphinx, 773. Syllis, 907. Sheep-Tick, 791. Sphyra>nid, 175. Siphonostoma, 887. Squid, 9fi4. Tanager, 389. Sipunculus, 1114. Sirenia, 285. Squilla, 865. Squirrel, 219. Tanystoma, 792, 795. Tape-worm, 925. Siren idee, 532. Stag, 262. Tapitelce, 829. Siricida*, 754. Stag-Beetle, 711. Tapir, 290. Siskin, 387. Skink, 502. Star-Fish, 1103. Star-gazer, 610. Tardigrada (Mamm.), 240. Tardigrada (Mites), 841. Skua Gull, 460. Starling, 395. Tarentula, 826. Skunk, 196. Steatornis, 406. Tarsius, 162. Skv-lark, 388. Stel/erida, 1103. Tawny Vulture, 378. Sloth, 240, 241. Stellio, 497. Teal, 455. Sloth Animalcule, 841. Stentor, 1217. Tectibranchiata, 1003. Slow-Lemur, 162. Sterlet, 596. Tegenaria, 829. Slow-Monkey, 151. Stickleback, 608. Teguexin, 499. Slow-Worm, 502. Stilt, 451. Teleosaurus, 488. Slug, 981. Stilt- Plover, 451. Teleostei, 601. Smelt, 634. Sting-Ray, 582. Telephorus, 712. Smooth Hound, 586. Stoat, 196. Tellina, 1039. ' Snail, 982. Stock-Dove, 428. Tench, 631*. Snakes, 506. Stomapoda, 863. Tenebrio, 713. INDEX. Ar. U. — The numbers refer to the paragraphs. 587 Tenrec, 178. Triffla, 608. Vampyre, 170. Trnthredinidte, 753. Trifflidtff, 608. Vanessa, 772. Tenuirostrea, 414. Trigonia, 1034. VaranidcE, 498. Terebella, 912. Trilobite, 874. Velella. 1195. Tfrebrautia, 752. Trimera, 721, 782. Venantes, 825. Terebratula, 1050. Triodon, 604. I'eneracecK, 1039. Teredo, 1044. Trionycidce, 485. Venerupis, 1039. Termites. 740, App* Tritoniadce, 1006. Venus, 1039. Termitidce, 740. Trochilidce, 415. Veretillum, 1156. Ter.-. 460. Trochus, 997. Vermetus, 995. Terricola, 913. Trogonidfe, 411. Vermiform Classes, 902. Testacella, 98 J. Trombidiidce, 840. VERTEBRATA, 60. Tt-stii'lini'ltg, 484. Tropic-Birds, 461. I'espertilionidce, 171. Tfthys, 1006. Tropidonotus, 506. Vespida, 761. Tctrabranchintn, 966. Trout, 634. Vicugna, 282. Tetracaulodon, 289. Trumpeter, 447. Vidua, 390. Tctramera, 715. Trumpet-fish, 607, Violet Snail, 999. Tetraodon, 604. Trunk-fishes, 605. riperidae, 512. Tetraonidee, 433. Trygonidce, 582. Viperine Snakes, 505, 511. Tenthida;, 618. Tubicola, 911. Virgularia, 1156. Thecosomata, 1013. Tubicola, 825. Viscacha, 235. Theli/plionidcr, 831. Tubiporidce, 1160. Viverrida;, 195. Thelphusa, 860. Tubularits, 1179. Viviparous Lizard, 500. Thoracica, 895, 896. TUNICATA, 1053. Vole, 228. Thornback, 581. Tunny, 614. Volvocinece, 1218. Thread-worm, 923. Tupaidce, 179. Volucella, 797. Thresher, 588. Turbellaria, 924. rolutidee, 987. Thrips, 734. Turbinidce, 997. Vorticella, 1217. Thrush, 402. Turbo, 997. Vorticellince, 1217. Thylacinus, 310. Turbot, 628. Vulturidte, 376. Thutanoura, 803. Turdidce, 402. Tick, 839. Turkey, 432. Ti-er, 188. Turkey Buzzard, 378. W. Timarcha, 719. Turnip-Flea, 719. Tinamidte, 435. Turnip-Fly, 753. . Waders, 443. Tinamou, 435. Turnstone, 446. Wagtail, 400. Tineida>, 778. Turrilite, 970. Walking- Leaf, 729. Tipulida;, 793. Turritellidee, 994. Walking-Stick, 729. Titlark, 400. Turtle, 485. Walrus, 203. Titmouse, 400. Turtle-Dove, 428. Wandering Spiders, 827. Toad, 528. Two-humped Camel, 278. Wauderoo, 155. Todid(B, 410. Typhlopidce, 503. Wapiti, 262. Tomicus, 716. Tongue-worms, 841. Typographer Beetle, 716. Tyrants, 403. Warblers, 399,400. Wasps, 761. Tooth-shell, 1001. Water-Boatman, 789. Top-shells, 997. U. Water-Bugs, 789. Tope, 586. Water- Flea, 879. Tornatellidtc, 1003. Torpedinidte, 583. Udonella, 919. Water-Mite, 840. Water-Mole, 317. Tortoise, 484. Tortoise Beetle, 718. Tortricidre (Kept.), 507. Tortricidce (Insects), 777. Toucan, 423. Touracos, 392. Unau, 241, Ungka-puti, 149. Unionido!, 1033. Upholsterer Bee, 764. Upupidv, 418. Uranoscopus, 610. Urchin 178 Water-Rail, 452. Water- Hat, 228. Water-Scorpion, 789. Water-Shrew, 177. Water-Spiders, 830. Waxwing. 404. Toxotes, 613. Weasel, 196. Toxodon, 303. Trachearia, 833. Trachelides, 714. Trachinidff-, 610. Tragopan, 432. Urodela, 530. l-rsal. 202. Ursidtv, 199. Ursine Dasyurus, 310. Ursine Opossum, 310. TTvaiic 1 QQ Weepers, 159. Weever, 610. Weevil, 715. Wentle-trap, 994. Whales, 211. Tree-Frog, 527. Tree-Pigeon, 428. ursus, i yy. Urus, 270. Utia 227. Whale-bone Whale, 214. Whale- Louse, 870. Trematoda, 924. •\\heatear, 400. Trepang, 1115. Wheel-Animalcule, 927. Trichecus, 203. V. Whelk, 9f9. Trichina, 923. Whidah finch, 390. Trichoptera, 747. Tridacna, 1036. Vaq antes, 827. Vaginicola, 1217. Whimbrel, 450. Whip-poor- Will, 4