570 T. TKEBA : 



not ill (lii'cct contact with, Imt separated l)y a considerable distance 

 from, the gnt. 



From the facts ahove stated, we are justified in conclndinji; 

 tliat the cfßcal capillaries are not produced as out-growths of the 

 dorsal vessel, hut are formed iudependently ])y cell-nniltiplicatiou 

 takiug place in certain parts (near the gut) of the ventral mes- 

 entery, and, theref)re, that the dorsal vessel and the ca])illartes 

 have ditferent origins. 



Next T will consider the origin of the ring vessel of the achdt 

 animah Although some early authors have frequently I'efcrred to 

 the so-called ring vessel of ActhiolrocJui. yet its origin, forui, aud 

 position have never l)een satisfactorily elucidated.'-' Nohody has 

 investigated it hy means of sections, and the statements which 

 have l)een made al)0ut it do not rest, it seems to me, on actual 

 anatomical studies of Actinolrocha, hut rather are mere inferences 

 from facts known respecting the metamorphosed larva. Conse- 

 quent! v there have been put forth several irreconcilde views in 

 I'cgard to the ring vessel. The structure desci'ibed under that 

 name bv C'lapap.ede, Schneider, Metschnikoff, and Caldwell 

 does not seem to be even one and the same thing. 



In order to make clear the relatious of this system of organs, 

 I nmst iirst of all descri1)e somewhat minutely the adult collar 

 cavitv. Tn the fully developed larva of every type, the rudiment 

 of that cavitv is represented by a circular space on the iinier 

 side of the tentacular row just above the septum. The space is 

 in form not a complete ring, but is interrupted at the median 



'" In passing I should say that Masteuman's ring sinuses have nothing to do witli the 

 vessel under consideraliou, because of tiiom tlic Iirst is stated to be priœsophageal, tlie second 

 peri-intestinal, and the third perianal in position; and thus tliey nuist be something entirely 

 different from the ring vessel of other authors, which is a sinu-^ in the splanchnic walls 

 aniuud tlic stoni;\ch. 



