Bryozoa.] 



MUSEUM OF ANIMATED NATURE. 



407 



tudes revel, performing a thousand evolutions, and 

 yet avoiding; each other in their mazy dance. They 

 evidently enjoy existence, and are highly organized. 



Fig. 3784 represents Brachionus urceolaris, one 

 of the Loricate group : a a. the rotatory cilia ; b, in- 

 ternal branchial organs ; (/, the eye ; e, gizzard and 

 jaws ; f, stomach ; g, appendages of stomach ; h, 

 egsr-sacs ; i, the tail. 



Fig. 3785 represents the same still more enlarged : 

 c, cilia; p, pharynx, or tooth-armed gizzard; e, 

 stomach ; a p, appendages to the stomach ; o v, 

 egg-sacs ; 7/j, muscles ; q, tail ; o. the eye ; b, inter- 

 nal branchiffi ; c a, branchial canal. 



Fig. 37S6, Notommatacentrura, one of the naked 

 Rotifera. The letters refer to the same parts as in 

 Fig. 3785. 



CLASS BRYOZOA, or MOSS CORALS. 

 The Moss Corals, or Ciliobranchiate Polypes of Dr. 

 A. Fane, are of a higher grade in the scale of or- 

 ganization than the simpler Polypesj with which 

 till recently they have been associated. They form 

 a numerous class. Hundreds of microscopic fossil 

 species have been recently detected by the labours of 

 Ehrenberg and D'Orbigny, and it would appear that 

 their shells or outer tunics enter into the composi- 

 tion of chalk-beds, compact mountain-limestone, 

 the flints of the Jura limestone, the sea-sand of Eu- 

 rope, the Mauritius, the Sandwich and other islands, 

 and the sands of the Libyan desert. Of these many 

 are invisible to the naked eye ; others resemble mi- 

 nute grains. Of these fossil forms many are still 

 living. Some idea of the extreme minuteness of 

 several of the fossil Bryozoa may be formed, when it 

 is known that multitudes are present in the finest 

 levigated whiting, without havmg suffered change 

 in the preparation of the chalk; and that when 

 spread out, mixed with water, a mosaic-work of 

 these animalcules, of varied and beautiful forms, 

 may be seen by means of a microscope. 



To the Bryozoa, according to Ehrenberg, must be 

 added the Foraminifera of D'Orbigny, which the 

 latter naturalist regarded as constituting a family of 

 the Cephalopodous -Mollusks, and allied to the Am- 

 monites. Of these Foraminifera, Milliola, Bilo- 

 culina, Rotalia, Rosalina, Nodosaria, Cristellaria, 

 &c., formerly considered as minute Ammonites, are 

 examples. Ehrenberg places them in his Polythal- 

 raic order of Bryozoa. For an able exposition of 

 Ehrenberg's system see the ' Annals and Mag. of 

 Nat. Hist.' .Tune, 1841, p. 296; and also the number 

 for July. With respect to Ehrenberg's views, we 

 have no space to discuss them, nor would such a 

 review be here in place. The Bryozoa differ from 

 the ordinary Anthozoa or Polypifera in possessing a 

 distinct alimentary canal, contained in an abdominal 

 cavity, and a circulatory system : there are distinct 

 muscular fibres to be detected by means of a power- 

 ful microscope, and also nervous filaments. As 

 examples of these curious animals we may enume- 

 rate Lunulites, Cellepora, Flustra, Eschara, &c. 



The genus Lunulites is known only in a fossil 

 state. These fossils present us with an arrangement 

 of cells with an opening above, disposed upon a 

 single stage in concave circles or diverging rays, 

 so as to form a cretaceous polypary (as the cells of 

 polypes are termed), of orbicular figure, convex 

 above, concave below. Fig. 3787 represents Lunu- 

 lites radiata, from Grignon, &c. : a, the upper side ; 

 c, the under side ; b, natural size. 



Fig. 3788 shows Defrance's " Lunulite en parasol," 

 the type of the genus Cupularia : a, a portion mag- 

 nified to show the cells in which the polypes re- 

 sided; c, three cells, more highly magnified ; 6, the 

 fossil, natural size. With these may be compared 

 the Nummulites lentieularis (Fig. 3789), one of the 

 fossil Foraminifera of D'Orbigny. 



With respect to Flustra, these Bryozoa vary very 

 much in the form and character of their polyparies ; 

 sometimes they appear as a cluster of minute cells, 

 extended on fuci, and resembling honeycombs in 

 miniature, as Flustra eriophora ; others form stems 

 or leaves of a horny texture, sometimes cellular on 

 one side only, sometimes on both. A large folia- 

 ceous Flustra common on our coasts (F. foliacea), 

 has cells of a pear shape on both sides ; these cells 

 have elevated margins, armed with spines. Fig. 

 3790 represents the Flustra foliacea: a, the na- 

 tural size ; h, some of the cells, magnified. The 

 extension of the cells of the Flustra takes place 

 laterally, those in the central part of each foliation 

 being often destitute of living polypes, while the 

 external ranges of cells are tenanted. There are, 

 hov.ever, limits beyond which the extension of the 

 polyparies of the Flustra does not proceed. In the 

 FliHtra Carbasea, found on the coasts of Scotland, 

 the cells are elongated. The polypes of this species 

 have been examined by Dr. Grant : he states that 

 the tentacles are twenty-two in number, with about 

 fifty cilia in a row down the sides of each : there 

 are about one thousand eight hundred cells on each 

 square inch of surface ; and the branches of an or- 

 dinary specimen present about ten square inches 



of surface, so that there are about eighteen thou- 

 sand polypes on a single zoophyte. On the Flustra 

 foliacea there are at least twice as many, all actively 

 employed working their tentacles, and vibrating 

 the cilia which cover them, in order to obtain 

 their food. 



Fig. 3191 shows — a, a portion of Flustra Carbasea, 

 natural size ; 6, a portion magnified. 



We have said that some of the Flustrse, instead of 

 being foliaceous, encrust other bodies. Fig. 3792 

 shows an encrusting species, the Flustra dentata of 

 the Northern Seas, magnified, with a representation 

 of one of the polypes protruded from its cell, with 

 its ciliated tentacles spread. 



Some Flustraj, we may add, are parasitic upon 

 others; on the Flustra foliacea, for example, a 

 parasitic Bryozoon takes its abode and spreads in 

 patches on its cellular fronds. This singular Bryo- 

 zoon is the Valkeria inibricata (Bovverbankia dcnsa 

 of Dr. Farre). As its structure lias been well inves- 

 tigated, we shall give an outline of it, in order to 

 elucidate the general structure of the polypes of 

 this class. The polypes of the Valkeria inhabit 

 each a transparent horny tube, about a line in length, 

 and clusters of these tubular cells rise from a com- 

 mon creeping base or stem. The polype, when 

 protruded from the orifice of its cell, spreads out 

 ten long slender tentacles, surrounding the mouth ; 

 on the outer face of each tentacle is a series of stiff 

 spines, and besides them a multitude of vibratory 

 cilia, which the little creature throws at will into 

 the most rapid movements, so as to produce a vor- 

 tex gyrating to the mouth. The mouth is simple, 

 leading to a capacious gullet, which, gradually nar- 

 rowing terminates in a muscular gizzard of a 

 rounded form, to which succeeds a long conical 

 stomach with glandular walls. The gizzard has 

 its inner membrane tessellated with minute teeth. 



The alimentary canal emerges from the upper 

 part of the stomach, and terminates below the base 

 of the tentacles. 



When the animal withdraws into its tube, two 

 muscles, rising from the tube, and inserted one into 

 the gullet, the other into the lower part of the 

 stomach, contract and throw the alimentary canal 

 into tortuous folds. But besides these two muscles 

 there is a set connected with the tentacular appara- 

 tus, for closing the tentacles. It must be here ob- 

 served that the cell itself may be divided into three 

 portions : first, a basal horny transparent portion, firm 

 and unyielding ; secondly, a soft flexible continua- 

 tion ; and thirdly, a marginal circle of bristle-shaped 

 appendages connected together by a filmy web, like 

 the rays of the fin of a fish. When the polype with- 

 draws itself, the tentacles are first folded up into a 

 close bundle and then ret racted, the oesophagus retir- 

 ing at the same time. With the descent of the oeso- 

 phagus the soft part of the tube begins to be inverted, 

 and the seta, or bristles, close together ; these are 

 drawn inwards till they disappear, the soft tubular 

 part forming a sheath round them ; the whole con- 

 stituting a sort of stopper shutting up the polype 

 in its horny case. 



Six distinct fasciculi of muscles, arising from the 

 hard portion of the tube, act upon the flexible por- 

 tion of the tube as retractors. 



The polypes of Flustra are modelled nearly upon 

 the same plan as those of the Valkeria (or ' oower- 

 bankia'), but their extreme minuteness and the 

 incomplete transparency of the cells render their 

 microscopic examination more difficult. 



It would seem as if a group of Rotifera rendered 

 stationary, with their cells united, so as to Ibrm a 

 foliaceous expansion, would be then so many Bry- 

 ozoa; and indeed there are not wanting links 

 which connect these two forms of life together. 

 Among other examples of the Bryozoa, we select 

 the Flustra avicularis, a native of the European 

 seas. 



Fig. 3793 shows a spherical mass of Flustra avi- 

 cularis, of the natural size. Fig. 3794; a, the root 

 and foliaceous form, of the natural size; 6 and c, 

 portions magnified. 



Fig. 379.) shows the polypary of Electra verti- 

 cella (Flustra verticellata, Gmelin) : a, the natural 

 size ; b, magnified. The polype is unknown. 



Fiff. 3796, Elzerina Blainvillii : a, the natural size : 

 b, magnified. Animal unknown. Locality, the 

 seas of Australia. 



Fig. 3797, Pherusa tubulosa (Flustra tubulosa) : 

 «, the upper side ; b, lower side ; c, a portion mag- 

 nified. 



Fig. 3798, Cellaria ceroides, from the Mediter- 

 ranean and Indian seas : a, the natural size ; b, a 

 portion of the lower part, magnified. 



Fig. 3799, Cellaria Salicornia, from the European 

 seas ; a, the natural size, b, a portion magnified j c, 

 a smaller portion still more highly magnified. 



Fig. 38()0, Cellaria loricata, of the natural size ; 

 and a branch magnified to show the cells. 



Fig. 3801, Cauda arachnoidea: a, the natural 

 size; 6 and c, portions magnified. This Zoophyte 

 Bryozoon is a native of the Australian seas. 



Fig. 3802, Caberea dichotoma : a, the natural 

 size ; b, two cells, magnified. 



Fig. 3803, Acamaichis neritina : n, the natural 

 size ; b, the lower poition, magnified, showing the 

 cells. This species is found in the Mediterranean. 



Fig. 3804, Geramicellaria bursaria: a, natural 

 size ; b, a portion magnified. Locality, the Euro- 

 pean seas. 



Fig. 3S05, Unicellaria chelata : a, the natural 

 size ; b, a portion magnified. Locality, the Euro- 

 pean seas. 



Fig. 380G, MenipaBa hyalina : a. the natural size ; 

 b and c, the cells, magnified. Locality, the Indian 

 seas. 



Fig. 3807, Eschara foliacea. The magnified por- 

 tions show the arrangement of the cells, on a fron- 

 descent or leaf-like pulypaiy. 



Fig. 3808, Andonea foliifera, a foliaceous species, 

 with minute cells, or leaf-like polyparies. 



Fig. 3809, Cellepora puraicosa ;.a spongy mass of 

 minute cells encrusting the branch of a zoophyte. 



Fig. 3810, Retipora cellulosa: a species with leaf- 

 like expansions, having the cells opening on one 

 face only. 



Fig. 3811, Discopora verrucosa. The two figures 

 show the species of the natural .size and magnified. 

 The cells are close and elevated, and encrust other 

 bodies. The polype is unknown. 



We may heie observe" that the Bryoziae, or Cilio- 

 branchiata, constitute the order Zoophyta ascidioida 

 of Dr. Johnson, and the family Operculifera, or 

 Eschariaja, of other naturalists. Though structurally 

 elevated above the ordinary Zoophytes, cr Phy- 

 toza? of Ehrenberg, which in their general mode 

 of existence, in their polyparies, and plant-likeaspect 

 they resemble, it will lie necessaiy, in .order to 

 understand this group of beings, to obtain clear and 

 precise ideas of the simple Polypes, between which 

 and the Rotifera and the stemmed Echinodermata, 

 or Encrinites, they seem to form a link of union. 



The simple or ordinary Polypes, Phytozoa, are 

 placed in the Acritous subkingdora, viz. that in 

 which no distinct nervous system is to be discerned; 

 to this subkingdom we will immediately direct our 

 attention, and beginning at once with the lowest 

 forms of animal creation, the Sponges, pass up the 

 ascending grades of existence which that sub- 

 kingdom presents. It is in this way only that we 

 shall be able to render the subject clear to our 

 general readers ; and at the outset, we must ad- 

 monish them, that the ideas of life and organization 

 which are derived from a consideration of the 

 higher classes of the animal world, where we find 

 nerves, blood-vessels, viscera, and muscles, must be 

 set aside. We are about to contemplate animal 

 life in its simplest phase, and, marking as it were 

 its dawn, trace up its primordial developments. 



Subkingdom ACRITA. 



The beings of this subkingdom, which, with the 

 exception of certain Entoza;, are all aquatic, pre- 

 sent us with varied forms; all however consist 

 essentially of a gelatinous and, it appears, homogene- 

 ous substance, of which the solid constituents bear 

 but a trifling proportion to the fluid. This homo- 

 geneous gelatine is sometimes unsupported by any 

 kind of framework ; in other cases, it either invests 

 a support or is contained in a sort of external case 

 or investment formed by the process of secretion. 

 In the substance of these animals no nerves have 

 been detected, but nervous molecules are probably 

 blended with it ; there are no true blood-vessels, 

 yet in some, canals are excavated in the substance, 

 through which fluids, absorbed, circulate and are 

 carried to a central cavity ; and this apparatus 

 fulfils at once the purposes of nutrition and aeration. 

 In some a more perfect digestive laboratory is 

 present, and a more definite respiratory apparatus. 

 In most, no muscular fibres are to be perceived, 

 yet of these many contract and expand their bodies, 

 and are furnished with moveable and sensitive 

 tentacles by which they 'seize their prey. Many 

 are capable of locomotion, but others are fixed like 

 the plant to one spot for life. Some secrete a fluid 

 of an irritating quality, which gives great pain to the 

 hand with which it comes in contact. There is 

 ordinarily no distinction of sexes, and reproduction 

 takes place either by the simple division of the 

 body, by granular ova, or genimules which become 

 detached iiom the parent body, the Ibrm of which 

 they ultimately assume. 



In many instances the Acrita form compound 

 animals : numbers united together, form a vital 

 whole, constituting one animal, if we regard it iu 

 \ some points ; but many, if we regard it in others: 

 Such are the Zoophytes, the Diphyes, and others. 

 In the case of the latter, the body consists of two 

 portions, a larger and smaller ; but the junction is 

 so slight, that it is almost impossible to understand 

 the nature of the connexion between them, the 

 more especially astheir separation is not destructive 

 of life. Leaving these general observations, we 



