402 



MUSEUM OF ANIMATED NATURE. 



[ECHINODERUATA. 



fully expanded and in motion, they afford a beau- 

 tiful spectacle. 



Fis;. :J762 represents the Difmpa subulata, allied 

 to Scrpula, but differine in having its tube free and 

 unattached to other objects ; the tube, moreover, 

 has an aperture at its posterior apex. From these 

 circumstances the Ditnipa has been confounded 

 with the molluscous dentalium and it is to Mr. 

 Berkeley (Zool. Joum.) that we owe our knowledge 

 of its real affinities. It is found in tine sand at 

 great depths in the British Seas, from sixty-four to 

 one hundred and seventy-one fHthoms. n, the ani- 

 mal out of its tube; b, one of the branchiae ; c, a 

 portion of the anterior part of the mantle; r/, the 

 surface of the operculum, or stopper. We may add 

 that this species, the Dentalium subulatum of Des- 

 hayes, occurs also arounil the shores of Madeira. 

 The Terebellae inhabit sandy shores half way be- 

 tween hii;h and low water, buried up to the orifice 

 of their tube in the sand. As the bed is liable to 

 shift from the action of the waves, these annelides 

 are sometimes covered deeply, and at other times 

 exposed. In the former case the animal works its 

 way to the surface, elonffatina: its tube as it pro- 

 ceeds; in the latter it must bury itself deep, and yet 

 continue its tube ; in these operations its tentacles 

 are of great importance. If one of the Terebellie 

 be deprived of its sand-tube, and placed in a ves-xel 

 of sea-water, with a bed of sea-sand and fragments 

 of shells at the bottom, it may be seen expanding 

 its tentacles to the extent of nearly two inches, and 

 dragging by their means particles of all sorts to- 

 wards its head ; with these it forms a ring round its 

 neck, cementing them together by a glutinous se- 

 cretion. During its labours it keeps bending the 

 head from side to side, adding to the collar, and 

 pushing up its body as it proceeds. Having formed 

 a collar of about an inch broad, it begins to burrow, 

 and directing its head against the sand, slowly 

 makes its way, availing itself of every fit particle to 

 add to the tube — so far the head is downwards. 

 Now, however, the tube being completed and fixed 

 in the sand, the annelide emerges from it, and re- 

 entering tail foremost, keeps its head uppermost, 

 thus reversing its position, in order that the bran- 

 chise may be exposed to the water, and the tentacles 

 employed in quest of food. Thus the tube is buried 

 in the sand, with a small portion only above the 

 surface. This process during summer requires 

 about five hours, but a longer time in winter, the 

 animal being less vigorous. 



The Annelidse, as far as we know, are oviparous ; 

 in the common earth-worm the eggs are about three 

 lines long, and somewhat oval ; they contain each 

 two yolks, a pair of young springing from every egg'; 

 these eggs have a sort of lid at each end, which opens 

 when the worms are mature, to permit their exit.,' 



^yith respect to the leech, a naked suctorial an- 

 nelid, we may observe that not only is it furnished 

 with a caudal disc, but the anterior extremity is ca- 

 pable of being used as a prehensile sucker. In the 

 centre of this oral sucker are three diminutive 

 but sharp teeth, and near the anterior margin (in 

 the medicinal leech) are ten very minute black 

 eyes, ranged in a crescentic manner, and probably 

 adapted only for very close vision. This facility, 

 however, is in all probability at a low ratio. 



Like the worm, the leech produces capsular eggs. 

 Some species in Chili and Ceylon are terrestriali 

 living in woods, where they crawl upon the leaves 

 and branches of shrubs, and the trunks of trees ; 

 and a European species, Geobdella trochetii, lives 

 as much on land as in the water. The ordinary 

 food of leeches appears to consists of minute ani- 

 mals, as tadpoles, aquatic worms and larvae, and de- 

 composed animal mattere. The leech-fishers of La 

 Brenne place bits of decayed flesh in the water, 

 round which these creatures crowd in shoals, and, 

 intent upon their food, are then easily captured. 

 We must pass, however, from this last class of the 

 Homogangliata, to another subkingdom. 



SuBKiNGDOM NEMATONEURA. 



The groups coinprehended in the present division 

 of the animal kingdom, thounh agreeing in certain 

 structural points, differ materially from each other 

 in general economy and external characters, inso- 

 much that many seem to belong rather to the acri- 

 tous subkingdom than to the present, in which the 

 nerves are apparent in the form of threads diversely 

 arranged. We allude particularly to the Coelemintha, 

 or cavitary intestinal worms ; the Bryozoa, or moss 

 corals, and the microscopic Rotifera. Yet have 

 these characters which elevate them above the 

 nerveless groups, both as respects structure and re- 

 production. We must not, however, enter into 

 anatomical minutiae. 



CL.'\SS ECIIINODERMATA. 

 (Echini, or Sea-Urciiins : Asterias, or Sea-Stars, 

 &c.) The Echinodermata are so called from the 



hedgehog-like spines with which certain species are 

 covered : the title however is but partially applicable; 

 indeed this class presents us with a series of forms 

 so modified by progressive transitions of character, 

 that were we to be shown an Encrinite. an Echinus, 

 and a species of Holothuria, or Fistularia, we might 

 be pardoned for questioning the affinity that is proved 

 to exist between them. Nevertheless, if we com- 

 mence with the Encrinite, in which a radiated body 

 is supported on a long stem, we shall find that by 

 progressive steps we may advance through Comatula, 

 Euryale, Ophiura, and others to Asterias, and thence 

 throuirh Scutella and others to Echinus. These 

 have all a tesselated calcareous covering, but in the 

 Holothuria we find a decided approach towards the 

 Annelides. The calcareous covering is changed for 

 a tough but irritable integument, a few thin calca- 

 reous laminie surrounding the mouth being the ves- 

 tiges of the shell developed to its maximum in the 

 Echinus. Leaving these general views, let us attend 

 to the various leading forms of which the present 

 class consists : and first", the Encrinite. 



The Encrinite belongs to the crinoid or lily-like 

 family of the Echinodermata, and is essentially a 

 tenant of the hotter seas. One minute species (Pen- 

 tacrinus Euroiiaeus) has been detected in the seas of 

 Europe attached to corals; but the tropical ocean 

 presents us with species of large size, and most 

 elegant appearance ; they are, however, extremely 

 rare, and few cabinets can boast of a specimen. 

 Most probably the long tesselated peduncle of these 

 creatures is attached to solid rocks or submarine 

 bodies at great depths, below the influence of the 

 turbulent waves ; there they twist about, and spread 

 their fringed arms in quest of prey, or clasp the 

 rock for additional security. There is a specimen 

 of the Pentacrinus Caput Medusae in the British 

 Museum, in that of the Royal College of Surgeons, 

 and in that of the Geological Society. It is a most 

 beautiful species, and exists in the seas of the 

 Antilles. 



Fig. 3763 represents the upper part or head of 

 Pentacrinus Caput Medusae. In the front two of 

 the arms are much smaller than the others, showing 

 that the animal had suffered mutilation, and that 

 the lost parts had been reproduced, though not 

 fully developed : a, the auxiliary side arms, articu- 

 lating at distant intervals, with the jointed column, 

 and also capable of being reproduced. 



Fig. 3764 represents the Pentacrinus Europaeus : 

 c, several individuals in different stages of develop- 

 ment, adhering by the base of their jointed column 

 to the stem of a coralline ; b, one of the individuals 

 expanded and magnified. According to Mr. Thomp- 

 son, this minute species, found on the coast of Ire- 

 land, is fixed by its stem to other bodies only in 

 early life ; he believes that it is in fact a Comatula, 

 and that in due time it becomes detached, loses its 

 stem, and moves freely at the bottom of the water, 

 creepingamonsrthe fronds of sea-weed. (' Proceeds. 

 Royal Soc' 1835,) 



The rarity of the Encrinite in the seas of the pre- 

 sent world is very singular, when we call to mind 

 the multitude of fossil species, and find whole 

 masses of rock consisting of their reliquia. At a 

 distant epoch of this planet, when its surface was 

 very different from what now obtains, and a high 

 temperature favoured the increase of beings the 

 rare analogies of which now exist only in the inter- 

 tropics, encrinites thronged the sea, from which our 

 older calcareous rocks were deposited. In Derby- 

 shire we find immense strata of Encrinite or Entro- 

 chite marble, replete with the exuviae of the crea- 

 tures which had lived and died, generation after 

 generation, through a long succession of ages, in 

 the spots where the geologist now collects them. 

 The broken joints of these entrochites are called 

 St. Cuthbeifs beads : they resemble small and 

 nearly solid wheels, with a cinquefoil orifice in the 

 centre. When |the outer coat of these fossil encri- 

 nites is destroyed, the central part or stipe, in which 

 was the living animal, of ligamentous texture, pre- 

 sents a series of circular equidistant plates round a 

 tubular axis. These relics are called screw-stones. 

 Tq some of the splendid fossil forms of this family 

 we would invite a moment's attention. Fig. 3765 

 represents the Lily Encrinite (Encrinus liliiformis), 

 or Stone-lily of the English ; its remains occur in 

 the Muschel-kalk of Germany ; at Hildesheim, Ra- 

 kenberg, &c. in Lower Saxony ; at Sewerven in 

 Westphalia; and the village of Erkerode in Bruns- 

 wick. Fig. 3766 represents another specimen ; a, b, 

 c, d, and e, different joints of which the stem is 

 composed. 



Fig. 3767 represents the Pentacrinus Briareus. 

 This rare and beautiful species occurs in the lias 

 and other strata of the oolite series, at Lyme, 

 Watchet, Keynsham, &c. : — a shows the head and 

 arms reduced; b, the upper part, of the natural size, 

 with the arms entwined around the plated integu- 

 ment of the abdominal cavity, which terminates 

 above by a sort of proboscis. 



The Encrinites maybe defined as Comatulae, with 



the disc prolonged into a stem, and divided into 

 numerous articulations, every part being strength- 

 ened by a mosaic of calcareous pieces, imbedded 

 in the living matter of which the animal consists: 

 each single arliculation is thus tesselated, the sepa- 

 rate portions being kept in juxtaposition by the 

 living body. The disc or centre from which the 

 arms radiate is also composed of several plates fitted 

 to each other. Of the internal structure of the 

 Encrinite little is known ; there is an injestive and 

 an ejestive orifice, as in Comatula, and it is 

 probable that there is a gastric cavity with an ali- 

 mentary canal convoluted around it. 



Both in Encrinus and Comatula the rays are beset 

 on each side with a row of firm jointed filaments, 

 adapting them admirably for the tenacious grasp of 

 their prey. In Comatula, which is free, they also 

 serve as locomotive organs, enabling the animal to 

 crawl along the sandy bed of the ocean. 



To the extinct fossil forms of Encrinite belongs 

 the Apiocrinites rotundus, found in the middle re- 

 gions of the oolitic series, and which is represented 

 restored (and reduced) at Fig. 3768. A, shows the 

 arms expanded ; B, the same closed ; a, the reme- 

 dial effect of calcareous secretions in repairing an 

 injury of the joints of the stem ; at the base of these 

 are two young individuals, and two truncated stems; 

 C, the pear-shaped body, divested of its arras ; D, a 

 vertical section of the body, showing the cavity of 

 the stomach, and a series of lower cavities or hollow 

 lenticular spaces continued down the stem; these 

 cavities are the moulds in which the screw-stones 

 are formed. Another form, Actinocrinites Triacon- 

 tadactylus (the Nave Encrinite of Parkinson), from 

 the mountain limestone, is represented at Fig. 3769 

 ^reduced) : a, the body and stem ; b, the body 

 divested of the arms. There are numerous other 

 fossil forms, the types of distinct genera. ■- ■ _ ' 



From the Encrinites let us pass to the sea-stars or 

 Stelleridae, of which, as we have said, the form near- 

 est to the previous group is represented by Coma- 

 tula. Fig. .3770 shows Comatula Adonae, from the 

 seas of New Holland. It is encircled byjten slender 

 rays or arms, fringed, with jointed filaments : A shows 

 the animal three-fourths the natural size, underside; 

 B, the same, upper side ; C, a portion of one of the 

 arms, with its fringe, magnified, under side ; D, the 

 same, under side ; E, one of the rays enlarged, 

 showing the terminal hook or anchor. 



From this form we may proceed to Euryale (Gor- 

 gonocephalus. Leach). Fig. 3771 represents the 

 Euryale sculata from the Indian seas : a, the back; 

 i, the front; c, a portion of the back ; d, the same, 

 front, natural size. Fig. 3772, Euryale costosa : a, 

 the centre, front view, natural size. This species is 

 from the American seas. Here we begin to trace a 

 development of the central disc. The arms are not 

 fringed, but most multitudinously branched, the 

 ramifications forming a network, in which prey is 

 enclosed and secured. In another species, however, 

 Euryale palmifera,the ramifications are less numer- 

 ous and terminal only. Fig. 3773 shows, a, Euryale 

 palmifera, front view ; b, the disc and part of arm, 

 front view, natural size; c, the same, back view; 

 d, extremity of one arm, natural size. Passing from 

 these we find in the Ophiurai a disc surrounded by 

 five slender arms, like the tail of a snake, squamous, 

 and unfurrowed beneath. Fig. 3774 represents 

 Ophiura texturata of the Kuropean seas : a, the 

 front ; b, the back ; c, a portion of centre and arm, 

 magnified, front ; d, the same, back. Fig. 3773, 

 Ophiura annulosa, from the Australian seas : the 

 back ; n, a portion of one arm, under surface, magni- 

 fied ; b, the same, upper side ; c, front view of 

 centre. Fig. 3776, Ophiura granulata of the Euro- 

 pean seas and the Atlantic generally : a, front ; b, 

 back; c, portion of arm, back view, natural size; 

 d, the same, front view. The Ophiurae are active, 

 and swim and creep with much facility in all direc- 

 tions, agitating the arms in a serpent-like manner. 



We may now advance to the true sea-slars, Aste- 

 rias, of which one tribe is radiated, having five arms; 

 of this the star-fish (Asterias rubens), so common 

 on our coasts, is an example. The other tribe con- 

 sists of the scutellated star-fish, or sea-stare, in 

 which the arms are short, often forming five acute 

 angles to an expanded body. Of this group the 

 Asterias tessellata, Fig. 3777, may be selected as an 

 example : it is widely distributed. 



And here, before passing to the Echinidae, we 

 may devote a short space to the general structure of 

 these animals, takmg the well-known sea-star of our 

 coast as an example. As we have said, it pre.senti 

 a disc and five rays. The external integument is 

 horny or coriaceous, with calcareous portions thickly 

 interspersed through its substance, forming spines 

 and tubercles on its surface. Along the trout or 

 under surface of the rays, and around the mouth, 

 there are rows of distinct moveable spines; but on 

 the back or upper surface they are in the form of 

 close-set conical eminences. This coriaceous, but 

 still flexible integument is tinted in various species 

 with difl"erent colours : in the common star-fish the 



