66 



THE ACALEPHAE. 



§Q2. 



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

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

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

 sometimes seen to contaiu fteces, seem to belong more properly to the 

 respiratory system.'"' 



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

 organ/^"' 



CHAPTER Vl 



CIRCULATORY SYSTEM. 



§ G2. 



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 HoUard, 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 represeutmg the 

 hepatic cells ; see Ann. d. Sc. Nat. III. 18-15, 

 p. 249, PI. IV. bis. 



9 The aquiferous canals of the respiratoi-y sys- 

 tem having been regarded as intestinal tubes, their 

 orifices, which in the Ctenophora are situated at 

 the extremity of tlie body, and in the Discophora 

 upon the borders, have been considered as anal 

 openings ; and especially so, suice in these two 

 orders, accidental imcca m these canals are expelled 

 through these orifices. See fVill, loc. cit. p. 2S, 



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

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



Ill Acalepha; possess an extraordinary digestive 

 power, whicli is the more singular as no secretory 

 organ has been found on the sides of their stomach. 

 j\Ierteii.s (Mun. d. I'Acad. de St. Petersburg, loc. 

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



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

 have seen in Cestum and Cydippe four vessels in 

 this situation, which are perhaps hepatic organs. 

 The orange-colored cords found upon the sides of 

 the stomach of Stephanomia, and which Milne 

 Edwards (Ann. d. Sc. Nat. 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 

 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. 



The variations in the shape and form of the di- 

 gestive apparatus are vfide and nmnerous, but 



their importance is. rather in Zoology. Stt Agas- 

 siz for the details oi Sarsia, Hippocrene, Tiarop- 

 sis, Staurophora, Pleurobraiichia, Bolina. — 

 Ed. 



t [§ 61, note 10.] Kulliker {Siebold and Kolli- 

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

 Velella and Porpita a glandular mass, correspond- 

 ing most probably to a liver. It had before been 

 reg.irded as such by Delle Ckiaje, but Kolliker 

 has given it a special description. It consists of a 

 brown mass which communicates with the bottom 

 of the stomachal cavity by branched, anastomosing 

 ducts. — Ed. 



