c6 



THE ACALEPHAE. 



$62. 



The AcalephjB have no true digestive tube. But, as such, has been 

 regarded a system of vascuhir canals filled with water, and which, de- 

 parting from the stomach, traverse the whole body. But these, although 

 sometimes seen to contain faeces, seem to belong more properly to the 

 respiratory system.'"' 



In none of the Acalephae has there been found anything like an hepatic 

 organ. '^"^ 



CHAPTER VI 



CIRCULATORY SYSTEM. 



§ 62. 



Until lately, the longitudinal and circular canals which, in some Acale- 

 phae, are spread out through the entire body, have been regarded as 

 belonging to a vascular, sanguineous system. But more recently these 

 have properly been considered as aquatic-respiratory organs, there having 

 been found, moreover, other vessels of exceedingly thin walls, and of a 

 sanguineous nature. 



These last constantly accompany and surround in a tubular manner the 

 aquiferous canals ; and it is quite rare that small branches are distributed 

 to the general parenchyma. 



The delicate walls of these vessels have neither longitudinal nor circular 

 fibres, neither are they lined with ciliated epithelium. They circulate a 



required to thoroughly settle this point. See below, 

 the respiratory organs. See also Hollard, who 

 unhesitatingly regards the canals, which, with Ve- 

 lella, communicate externally by a central opening, 

 as a digestive cavity, and thinks he has observed 

 in their walls brownish spots representing the 

 ■hepatic cells ; see Ann. d. Sc. Nat. III. 1845, 

 p. 24it, PI. IV. bis. 



U The aquiferous canals of the respiratory sys- 

 tem having been regarded as intestinal tubes, their 

 orifices, which in the Ctenophura are situated at 

 the extremity of the body, and in the Discuphora 

 upon the borders, have been considered as anal 

 openings ; and especially so, since in these two 

 orders, accidental fajces in these canals are expelled 

 through these orifices. See fVill, loc. cit. p. 28, 



and Ehrenberg, Abhandl. d. Berl. Akad. 1835, p. 

 189, Taf. I. IV. tig. 2, z* 



W Acalepha3 possess an extraordinary digestive 

 power, which is the more singular as no secretory 

 organ has been found on the sides of their stomach. 

 Mertens (Mem. d. I'Acad. de St. Petersburg, loc. 

 cit. p. 490, Taf. I. flg. 5, 6, a. ; and p. 518, Taf. 



VIII. tig. 4, Taf. IX. fig. 1, f.), however, affirms to 

 have seen in Cestum and CytUppe four vessels in 

 this situation, which are perha)js hepatic organs. 

 The orange-colored cords found upon the sides of 

 the stomach of Stephanomia-, and which Milne 

 Edwards (Ann. d. Sc. JVat. XVI. p. 222, PI. VII. 



IX. X.) has taken for genital organs — may they 

 not also be hepatic organs .' t 



* [§ 61„note 9.] Upon the nutritive system of 

 the Acalephae, see Forbes (loc. cit. p. 4), but 

 «specially Agassiz (loc. cit.), who has studied the 

 subject with conscientious care. There is no dis- 

 tinction between the alimentary canal proper and 

 the vascular system, for the one opens by large 

 tubes into the other. The Acalephs, therefore, cir- 

 culate chyme, and here we have the rudest form 

 of circulation. If this idea is once well considered, 

 the relations of their nutritive apparatus in general 

 will be quickly appreciated. 



The variations in the sliape and form of the di- 

 gestive apparatus are wide and numerous, but 



their importance is rather in' Zoology. See Agas- 

 siz for the details oi Sarsia, Hippocrene, Tiarop 

 sis, Staurophora, Pleurobranchia, Bolitia.-^ 

 Kd. 



t [§ 61, note 10.] Kolliker (SieboM.and Kolli- 

 ker''s Zeitsch. IV. Hft. 3, 4, p. 313) has observed with 

 Velella and Porpita a glandular mass, correspond- 

 ing most probably to a liver. It had before been 

 regarded as such by Delle Chiaje, but Kolliker 

 has given it a special description. It consists of a 

 brown mass which comnmnicates with the bottom 

 of the stomachal cavity by branched, anastomosing 

 ducts. ^ D. 



