170 CTENOPIIOR^. Part II. 



hitructure does not justify the supposition that the auricles are strictly homologous 

 to the marginal tentacles of tlie Discophorte ; but, at the same time, it should 

 not be overlooked that they are a prolongation of the amljulacral tubes of their 

 sphoromeres, and to that extent they bear homological relations to the marginal 

 tentacles of the Discophoraj. 



Remote as the com2)arison may seem, it cannot be douljted, upon reflection, that 

 the simple radiating tulx's of tlie naked-eyed Medusa^ and those of the medusoid 

 individuals of the Sijihonophora^ are strictly homologous to the ambulacral tubes 

 of the Ctenophora?, as they are also to those of the Discophora? proper. Their 

 number generally coincides in the Ctenophoraj and higher Discophorte, though there 

 are only four in the Siphonophora^ and most Hydroids proper. Sometimes they 

 are, however, very numerous in the latter, as we frequently find an indefinite 

 repetition of identical parts in the lowest representatives of almost every type. 



We have already seen that the peripheric branches of the chymiferous system 

 do not oj^en outward, as Ehrenberg and Milne-Edwards supposed ; but there are, 

 unquestionably, openings in its axial prolongation, in Ctenophora^, which have gen- 

 erally been considered as anal ajjertures. Milne-Edwards has accurately described 

 them in LeSueuria, and they have Ijeen observed by all later investigators. Les- 

 son alone has mistaken accidental openings in the circumscribed area for structural 

 features. There can be no doubt of his mistake, since he descrilies those holes in 

 the Beroids proper as surrounded Ijy fringes, while the position of the natural 

 openings of the abactinal pole of the Ctenophoiw is outside of the area, as well as 

 outside of the fringes which encircle it. In all the Ctenophorai which I have exam- 

 ined, I have invariably found two such openings, in an excentric position, one on 

 one side and the other on the other side of the antero-posterior diameter, and 

 oblicjuely oitposito to one another. Gegenbaiu" states that there is only one such 

 opening in the species which he has examined with reference to this point. It is 

 much to be regretted that he should not have mentioned its 2:)Osition ; for if the 

 opening Avhich he saw Avas excentric, as I have always found these openings to ))e, 

 I should infer, that while he saw one gaping and shutting, the opposite one may 

 have remained closed, as it sometimes does for a considerable length of time. 

 Gegenbaur further affirms that water may be admitted into the system through 

 that opening. I have only seen the openings gaping to discharge parts of the 

 contents of the funnel, and never oljscrved an inward current of the surrounding 

 medium. But whether these holes are siniplj- discharging openings, or at the same 

 time aflerent apertures also, it is ecjually important to consider their relations to 

 the whole system more fully than has generally been done. 



The Ctenophora are very greedy, and do not spare their own kindred ; Init, 

 generally, they feed on diflerent kinds of Acalephs and a variety of small marine 



