4t 



POLYZOA. 



POLYZOA. 



perifutric space, but which msy toon be wen to take a development 

 HI an outward direction. The bud now present* the appearance of a 

 TMioh projecting from the exterior of the parent-cell, closed t its 

 external or free extremity, but having ita cavity in communication 

 with the perigastrio space. The polypide is gradually developed iu the 

 interior of the gemma by the differentiation of ita fine granular 

 content*, and the extremity of the bud ultimately opens so as to 

 admit of the exwrtion and retraction of the young animal. Thus is 

 produced a fresh cell of the polyzoary, whose ultimate form, as has 

 been before observed, depends upon the point of the cell at which the 

 bud springs. This differs in almost every species, and upon this 

 difference depends the diverse physiognomy of the various species. 

 For instance, if each cell pullulate* at a single point at the upper and 

 back part, a polyioery, consisting of a single series of cells, such as 

 that of Jitta, or of //ij.poUa (fg. 6), will be presented ; if from each 

 crll two are given off and remain in close apposition, a circularly 

 expanded disc of greater or less regularity will be produced, as seen 

 in Ltjavlia (Jig*. 16 and 15o), some Membrimipora, ate., and so on. 



2. Reproduction by Ova. All the fresh-water, and probably, also, all 

 the marine Polysoa, produce true ova, which are formed in a definite 

 organ or ovary ; and from the existence of a true ovary and of ova, we 

 are at once fed to expect the co-existence of a male organ. That a 

 testis is present in all the species of fresh-water Polyzoa, at any rate, 

 no doubt, according to Professor Allinan, can be entertained, and in 

 taytmctUa (Farrtlta) repent, the existence of this organ is described 

 and figured by Van Beneden. In Paludictlla Professor All man says, 

 that the ovary and testes are both found in the same cell. The 

 former is an irregularly shaped body, adherent to the inner surface of 

 the endocyst, towards the upper part of the cell. The testicle is an 

 irregularly lobed mass attached, like the ovary, to the inner surface of 

 the endocyst. It occupies a position near the bottom of the cell, and 

 is thus separated by a wide interval from the ovary. Both organs are 

 attached to the ride of the stomach by a cylindrical cord. The form 

 of the ovary in the proper Uippocrepm would appear more to resemble 

 a moniliform cord. In Laguncula (farrdia), occording to Van Beneden, 

 the ovary and testis, in form and situation would seem very closely 

 to resemble those in J'alutlicelta. It would appear also that the 

 impregnation of the ova is effected by their escaping from the ovary 

 into the perigastric cavity, where they are brought into contact with 

 the spermatozoa, which have in like manner escaped from the testis 

 into the same cavity, and are swimming actively about in vast numbers 

 in the fluid with which it is occupied. There does not appear to be 

 any special opening for the escape of the ova after impregnation, 

 which it probably effected by a rupture in some part of the endocyst. 

 The forms of the ova vary a good deal in different genera, and in some 

 cases they are ciliated. 



8. Professor Allman also describes a mode of reproduction by free 

 embryoea, but does not seem to have noticed their mode or plan of 

 development. , 



The embryo upon ita escape from the ovum appears sometimes to 

 be ciliated, sometimes not. In the case of Lepralia coccinea, a cbeilos- 

 tomatous species, the appearance of an embryo of the ciliated kind 

 and ita subsequent development are well described by Mr. Oosse. 

 (' Naturalist's Rambles on the Devonshire Coast,' p. 218.) 



But although the above brief description of the reproduction of the 

 Polyioa by ova formed and impregnated within the perigastric sac be 

 Undoubtedly correct, as applied not only to the species in which it 

 has actually been observed, but from analogy to others as well, it 

 cannot be denied that very considerable obscurity rests upon the 

 mode in which the ova are developed in the uvicells or receptacles, 

 which have received that name, and as to the relation which those 

 Organs bear to the rest of the animal. There can Ira no doubt that 

 these organs do contain an ovum or ova, and that these ova are 

 developed, ab origine, in them, and there undergo segmentation ; but 

 how these ova are fertilised, and why a difference so great as this in 

 the position of the ovigerous organ should exist in apparently closely 

 allied genera or even species, is at present inscrutable. 



Section III. Classification. 



The more general relations of the Polytoa having, as before ob- 

 served, been described under the head of MOLT.USCA, the remainder 

 of this article will be devoted to the mode in which they may be 

 conveniently arranged among themselves. 



With our present defective knowledge of many particulars respecting 

 the conformation of the Polypidci, the classification of the Polyzoa 

 can only be attempted with any prospect of useful results, from the 

 study of the Polyxoary ; that is to say, so far as regards the deter- 

 mination of the subordinate groups the orders themselves being 

 defined by characters derived from the Polypide, or soft portion 

 of the animal The following scheme, which in ita main features has 

 been long received, appears to offer as convenient, and so far as our 

 present acquaintance with the subject allows, perhaps as natural a 

 classification as can be expected. 



Class POI.V/OA. 



Social molluscous animal*, whose nervous system consists of a 

 single post-oooophageal ganglion, with branches, but without a nervous 

 ring around the (esophagus ; and without any special organs of sense 



or of circulation. Mouth surrounded more or less completely with 

 a single row of ciliated tentacles. 



Polyzoa, J. V. Thompson, 'ZooL Research.,' Mem. 5, p. 92 (1830). 



Bryotoa, Ebreub., < Corallen-Thiere des Roth. Meer,' 1831 (1834 '). 



Molluican Zoophyta, seu Zoophyta Atcidioida, Johnston, ' Mag. 

 ZooL and Hot,' 1836. 



CiliobraMa(a, Farre, 'Phil. Tram.,' 1837. 



Order I. Po!y:oa infundibulata, Qervais. 



Tentacles disposed on an uninterrupted annular lophuphoro, sur- 

 rounding the unarmed mouth. 



Sub-Order I. CheUotlomata. 



The cresceutic subterminal mouth of the coll is furnished with a 

 moveable lip, by which it is closed when the animal retreats. 

 Escharadn', Fluitrada; Cdlariados (ex. Critia), Fleming. 

 Polypiaria operculifcra ct cdlaricca (ex. Critia), Blaiuville. 

 Ji'ickarina, Celleporina, Khreuberg. 

 Urccvlata (pars), Hagenow. 



A. Cells disposed iu a single series. 



Family 1. CalcniccUida:, Busk. 

 Cells connected by short flexible tubes. 



Gen. 1. Calenicdla, Blainv. (F'ujt. 1, 2.) 



Cells connected by short corneous tubes, all facing the same way ; 

 polyzoary phytoid, erect, dichotouiously -branched ; cell at the bifur- 

 cation geminate. 



a. fenatrata. Cells feneatrate in front ; ovicells terminal. 

 (8. YUtatce. Cells with a narrow elongated bond or vitta on each 

 side in front ; ovicells galeriform, not terminal. 

 Catenicella, Blainville ; ' Brit Mus. Cat,' p. 3. 

 Catenaria, Savigny, ' Egypt,' pi. 13. 

 About seventeen species known ; mostly Australian. 



1, Oalenictlla taurina. 3, Oatenittlla elrgant ; a, gemlnnto cell. 8, Oal/ii-limn 

 ornnlam. 4, Salieornariit farciminoida ; a, avicularium. 5, Cr!llar*i 1'eacM ; 

 a, ovicoll. 



Oen. 2. Alyiidium, Busk. 



Cells connected by short corneous tubes. Two cells arising from 

 each cell at a bifurcation. 



Alyiidium, 'Brtt, Mus. Cat,' p. 18. 

 Three species known. 



Oen. 3. Calpidium, Busk. (l-'ig. 3.) 



Cells with an avicularium on each side; each cell with three distinct 

 apertures, arising one from the upper part of another in a linear 

 series, connected by short corneous tubes. 



