48 



THE POLYl'I. 



^*^ 40, 41. 



§ 40. 



All Anthozoa and Bryozoa have a proper circulation ; for there rises 

 and falls in the cavity of their body a liquid, which is usually clear, and 

 often contains round and colorless corpuscles; This rises even to the end 

 of the cavity of the tentacles, and then returns into that of the body 

 generally. In the colonial Polyps, these currents, by traversing the canals 

 of the corallum, thereby pass from one animal to another. This movement 

 is caused by ciliated epithelium, which, as we have just seen, lines all the 

 cavities of these animals. 



With the Bryozoa, the cavity of whose stomach does not communicate 

 with that of the body, these currents are continuous, regular, and have a 

 definite direction. But with the Anthozoa they are changed by the 

 reciprocal action through the stomachic orifices of the liquids of the 

 stomach and cavity of the body. These currents are perceived in the 

 arms, even when the cavities of these organs open directly into the 

 stomach. <'* 



§ 41. 



Nothing can yet be positively said as to the nature of this circulating liquid, 

 for it is still doubtful whether this whole phenomenon should be regarded 

 as an aqueous or a sanguineous circulation. If we refer to the fact that the 

 Anthozoa can introduce water into the system through the apertures of the 

 stomach, it should be admitted that this system has an aqueous character, 

 performing, perhaps, the function of an internal respiratory apparatus, 



given o£f from the eight principal longitudinal 

 vessels numerous lateral branches, which anasto- 

 mose freciuently in the canals of the corallum, and 

 finally form a capillary net-work. The white, 

 semi-transparent corpuscles contained in thin 

 blood have, according to fVill, a diameter of 

 about 1-1200 of an inch, and out of the vessels 

 have a globular aspect. According to this same 

 observer, there is a similar vascular system in 

 Actinia.* 



1 The circulation in question has been observed 

 by many investigators. Trembley (Mem. pour 

 servir & I'Histoire des Polyps, p. 219) has per- 

 ceived it in Plumatella cristata. Dumortier 

 (Mem. sur I'Anat. et la Physiol, des Polypes, p. 47) 

 has confirmed this observation. Cavolini (see his 

 Memoir on the Anthozoa, p. 56, 87) has seen it in 

 the tubes of several Sertularina. There are various 

 opinions as to the cause of these currents. Gruit- 

 huisen (Isis. 1S28, p. 506) studied them in the 

 arms of Hydra., and regarded them due to a com- 

 munication with a circular vessel surrounding the 

 mouth. But, according to the observations of 

 Meyen {Brown's Miscellaneous Botanical writings, 

 IV. p. 490), of Ehrenberg (Mittheil. aus. d. Ver- 

 handl. d. Gesellsch. naturf. Freunde z. Berlin, 

 1836, p. 27) and myself, the cavities of the arms 

 open directly into the stomach. 



The movements of the liquid in the arms of Hydra 

 are due not only to the general contractions of the 

 body, as Gruithuisen and Meyen have supposed, 

 but also to the cilia covering these parts. This 



was first pointed out by Grant (The new Edinb. 

 Phil. Jour. 1827, p. 107 ; or Outl. of Comp. Anat. 

 1841, p. 430), who observed these currents in 

 F/ustra, Lobularia, Virgiilaria and Pennatula. 

 Nordmann, who has examined this circulation in 

 the body and tentacles of Alcyonella diaphana, 

 and Plumatella campanu'/ata, and other Bryozoa, 

 did not find any cilia. He compared the currents 

 to those seen in the joints of Chara (Microg. 

 Beitrag II. p. 75, or Obser. sur la Faune Pontique, 

 I). 709). I feel positive about the presence of cilia 

 in the body of Cristatella mirabilis and Alcyo- 

 nella -itagnorum. Lister has carefully described 

 this circulation with Tubularia, Sertularia and 

 Campanularia ; and finding no adequate cause, 

 has likened it to that of Cliara (Pliil. Trans. 1834, 

 p. 366, et seq.). Ehrenberg (Abhandl. d. Berl. 

 Akad. 1832, p. 299) and Loven (fViegmann\i 

 Arch. 1837, I. p. 254) attribute these currents in 

 Sertularia and Campanularia to a peristaltic 

 movement of the canals of the body ; which, how- 

 ever. Van Benedcn (M6m. sur les Campan. loc. 

 cit. p. 18) has been unable to see in these Polyps. 

 Erdt (Mailer's Arch. 1841, p. 426) attributes it, 

 in Feretillum cynomorium^ to cilia ; and IVill 

 {Froriep's neue Notizen, 1843, No. 599, p. 69) has 

 found all the cavities of the body and corallum of 

 Alcyonium palmatum lined with cilia. It is, 

 moreover, certain that the currents observed by 

 Erdl (Mailer's Arch. 1841, p. 428) and Dumor- 

 tier (Mem. loc. cit. p. 52) in the tentacles of 

 Actinia are due to ciliary action. 



* [ § 39, note 1.] Subsequent researches-have 

 failed to detect any true circulatory system with the 

 real Polyps, and there now can be but little doubt 

 that DO such system exists. As witli the Acalephs, 



their nutritive and digestive systems are combined; 

 and, as with them also, the ch'culating, nutritive 

 liquid is chyme. See also Dana loc. cit. i). 35. 

 — Ed. 



