66 



THE ACALEPHAE. 



<§>G2. 



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

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

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

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

 respiratory system.'"* 



In none of thft 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 genend parenchyma. 



The delicute 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 Fe- 

 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. 1815, 

 p. 2i0, PI. IV. bis. 



a The aquiferous canals of the respiratory sys- 

 tem having been regarded as intestinal tubes, their 

 orifices, which in the Ctenophora are situated at 

 the extremity of the body, and in the Discophora 

 upon the borders, have been considered as anal 

 openings ; and especially so, since in these two 

 orders, accidental tieces in these canals are expelled 

 thi'ough these oriiices. See fVill, loc. cit. p. 28, 



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

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



11' Acalephfe jiossess an extraordinary digestive 

 power, which is the more singular as no secretory 

 organ has been found on the sides of their stomach. 

 Mertena (Mtm. d. I'Acad. de St. Petersburg, loc. 

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

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

 have seen in Cestum and Cydippe fonf vessels in 

 this situation, which are perhajis hepatic organs. 

 The orange-colored cords found ui)on the sides of 

 the stomach of Stepkanomia, and which Milne 

 Edwards (Ann. d. Sc. Nat. XVI. p. 222, PI. vn. 

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

 not also be hepatic organs ? t 



* [§61, note 9.] Tpon the nutritive system of 

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

 especially 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. 



Tlie variations in the shape and form of the di- 

 gestive apparatus are wide and numerous, but 



their importance is rather in Zoology. See Agas- 

 siz for the details of Sarsia, Uippocrene, Tiarop- 

 sis, Stauropkora, Pleurobranckia, Bolina. — 

 Ed. 



t [5 61, note 10.] Kolliker (Siebold and Kiilli- 

 ker^s Zeitsch. IV. lift. 3, 4, p. 313) has observed with 

 Velella and Porpita a glandular mass, correspond- 

 ing most probably to a liv.er. 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 communicates with the bottoj* 

 of the stomachal cavity by branched, anastomosing 

 ducts. — Ed. 



