46 



THE POLYPI. 



^37. 



Polyps are placed in direct intercommunication. It is not rare to find 

 this general cavity divided into chambers by mesenteric membranes stretch- 

 ing longitudinally from it to the external surface of the stomach.''" 



The base of the stomach of many, and perhaps all of the Anthozoa, is 

 pierced by one or more valvular openings, which communicate with the 

 cavity of the body.**' These animals, by controlling at will these orifices, 

 can allow to pass into the cavity of the body the proper materials, which 

 are probably water and liquid chyle."'' This digestive apparatus thus com- 

 municating with the cavity of the body, reminds one of the organization 

 of the Infusoria.'"' 



The cavity of the stomach is lined by very delicate ciliated epithelium, 

 which is continuous through the orifices upon every surface of the cavity 

 of the body and arms, and even into the intercommunicating canals of the 

 corallum. 



The color of the walls of the stomach is quite varied, and is due to cer- 

 tain pigment cells which very probably perform the function of a liver ; 

 for these animals arc entirely wanting in any other glandular appendix of 

 the alimentary canal, analogous to a liver.**' 



4 There are often eight of these longitudinal 

 chambers, as in f^ereCillum, Alcynnium and Al- 

 cyonidium (see loones zoot. Tab. XXXIV. fig. 2 ; 

 also .-Ynn. d. So. Nat. IV. 1835, pi. XVI. fig. 3, and 

 pi. XII. fig. 3, 4). In Actinia there are seven 

 more. With Edwardsia the eighth mesenteric di- 

 visions do not reach the sides of the body {Qua- 

 trefa^es loc. cit. pi. I. fig. 2).* 



5 These orifices were long ago observed by the 

 elder anatomists upon various Polyps. After- 

 wards their existence was incorrectly doubted by 

 other naturalists ; for lately they have been dis- 

 tinctly made out. Thus, in Feretillum cynomo- 

 rium (Rapp, Nov. Act. physico-raedica XIV. 1829, 

 p. 650), in Alcyonidium and Alcyonium (Milne 

 Edwards, Ann. d. Sc. Nat. IV. p. 325, pi. XV. fig. 

 6), and in Edwardsia (Quatrefages Ann. d. Sc. 

 Nat. XVIII. p. 91). 



In Sertularia and Campanu/aria there are 

 openings between tlie stomach and the tubulou3 

 cavities of the corallum (Lister, Phil. Trans. 1834, 

 p. 371, and Ka« Beneden, Mem. sur les Campanu- 

 laires, loc. cit. p. 17). There must be direct com- 

 munication of tliis kind with the Actiniae, since 

 they regularly reject by their mouth nettling fila- 

 ments, from the chambers of their body. With 

 Hydra, the stomach communicates, by an orifice 

 situated at its base, with the narrow tubulous cavity 

 of its cylindrical foot. But at the extremity of this 

 tube there is no oval opening, and the tube itself can- 

 not be regarded as a rectum, for it receives neither 

 faeces, nor fragments of food, and is not affected by 

 the frequent enormous dilatations of these animals 

 from surfeit. Corda therefore is incorrect in as- 

 signing an anus to these animals. (Nov. Act. phvs- 

 ico-medica XVIII. p. 302, Tab. XIV. fig. 2, E ) He 

 appears to have entirely neglected the foot of this 

 animal, which, however, has been well figured by 

 Ehrenberg (Abhandl. d. Berl. Akad. 1836, p. 134, 

 Taf. II. fig. I); and since Roesel (Insektenbel. III. 

 Taf. LXXVIII. and L.XXIX. fig. 2, and LXXXVI. 

 LXXXVIII. fig. 6) has perceived it in all uimiuti- 

 lated arm-polyps. Sars (Faun, littoral. Norveg, p. 



* [§ 37, note 4.] With all the Actinaria the lam- 

 ellae of the visceral cavity are the multiples of 

 six ; all the .^Icyonaria have eight of these lamellae. 

 See Dana loc. cit, p. 49. — Ed. 



t [ § 37, note 5.] With the Actinoidea, recent 

 researches have shown that the stomach communi- 



21) has found with a Lucemaria a stomach opening 

 inferiorly, and communicating directly with the 

 cavity of the body. This communication has been 

 observed also by Frey and Leuckart (Beitr. p. 

 3)with the ^cimz'ae and several other Anthozoa. t 



6 quatrefages (Ann. d. Sc. Nat. XVIII. p. 87, 

 91) has seen the stomach of Edwardsia entirely 

 filled with Spirorbis, and other solid food, without 

 any of it passing into tlie cavity of the body. 



" With Infusoria, the lower end of the oesophagus 

 is free, so that the food passes directly from it into 

 the parenchyma of the body, where it forms a cav- 

 ity ; but with the Anthozoa, there is a stomach, 

 from which chyle alone can pass into the cavity of 

 the body. 



s These cells are white in Edwardsia, yellow in 

 Alcyonidium and Alcyonium, and orown in Vere- 

 tillum and Hydra. In the last, the brown is dis- 

 tinctly due to irregular pigment granules of that 

 color, floating in the clear liquid of the cell. Prob- 

 ably these cells, by bursting, empty their contents 

 into the stomach ; at least, I have been able to find 

 no excretory duct, such as Corda has figured with 

 the Hydra fusca (Nov. Act. Acad, physico-medica 

 XVIIl. p. 302, Tab. XV. fig. 15—17 ; or Ann. d. 

 Sc. Nat. VIII. p. 366, pi. XIX. fig. 15—17). 



In Hydra viridis, these brown cells of the stom- 

 ach can easily be distinguished from the layer of 

 green pigment belonging to the parenchyma of the 

 body. Moreover, if a transverse section of this 

 animal is made, there appears a wide difference of 

 organization between the internal and external sur- 

 face of the stomach; the first has ciliated epithe- 

 lium and hepatic cells, the second a bare skin with 

 prehensile organs. This being so, how can these 

 animals be everted like the finger of a glove, as some 

 naturalists have affirmed, and yet live ? for the two 

 surfaces of the stomach, so different, could not re- 

 place each other, and then again the cavities of the 

 arms would open directly outward. Indeed, it is 

 not possible to return unmutilated an everted 

 Polyp, since the inextensible cavity of its foot can- 

 not leave the body with impunity. The gastric 



cates with the cavity of the body by a single ori- 

 fice only, which may be closed by muscles. See 

 Dana, loc. cit. p. 40, 44, pi. XX.K. fig. 3, a, b, c, d. 

 It has been since verified by Cobbold, Ann. Nat. 

 Hist. XI. 1853, p. 121, with figures. — Ed. 



