ANATOMY OF CESTODES. 183 



communicating on each side with the cirrus-sac. This erroneous 

 statement, however (made upon the examination of poor material), 

 is corrected in accordance with the criticism of Cohn in a later 

 note *. 



A more correct account of the water-vascular system of 

 Amabilia is given by Cohn in his memoir. This is also illus- 

 trated by three figures. In many respects I find myself in 

 agreement with Cohn ; but differ in some important respects. 

 As he has stated, the dorsal vessel is of much less calibre than 

 the ventral, a usual occurrence among the Cestodes ; and be- 

 tween the two the cirrus-sac makes its way to the exterior. 

 Thus the dorsal and ventral vessels are at opposite sides of the 

 proglottid and are, in fact, respectively dorsal and ventral in 

 position, as is also frequently, but by no means always, the case. 

 The transverse vessel that is figured by Cohn is alleged by him 

 to be a single vessel which on each side enters the vertical trunk 

 (described originally, and correctly, by Diainare) near to the 

 dorsal external pore of the latter. It bends upwards to reach 

 this point on either side not far from its opening into the vertical 

 tube. During the rest of the proglottid the transverse vessel is 

 fairly median in position ; it lies also near to the posterior 

 boundary of the segment. There is not the least trace in Cohn's 

 figure f of a double transverse vessel ; nor does he describe such. 

 But this tube is most obviously double. 



Cohn has described in the posterior region of each proglottid 

 a union between the dorsal and ventral vessels ; this " verbind- 

 ende Kanal " is, he says, continued into the transverse vessel 

 which ultimately opens into the vertical canal. My own pre- 

 parations do not confirm this statement. There is certainly a 

 communication between the dorsal and ventral lateral vessels 

 where it is described by Cohn as occurring ; but the larger ventral 

 and the very much smaller dorsal vessels are in each case near the 

 point of communication between them, continuous with a dorsally 

 placed and narrower and a ventrally placed and wider transverse 

 vessel. These lie (text-fig. 5) very close together and retain the 

 same mutual position until they open into the vertical vessel. 

 They do not, however, as would be inferred from Cohn's drawings, 

 enter this tube laterally, but on the posterior surface, as is 

 indeed shown by Diamare. though, as I have already pointed 

 out, he mistook at first the nature of the tubes in question. 

 I should add that the dorsal and ventral separate moieties of the 

 transverse vessel unite just before their opening into the vertical 

 tube. 



In their comprehensive works upon the genera of Tseniadae, 

 both Fuhrmann and Ransom accept with a query the statements 

 of Cohn concerning the vertical tube. This doubt is, as I think, 

 caused by the fact that Cohn in figuring that tube only indicates 



* Centrabl. f. Bait, u. Paras, xxv. p. 357. • 



t Zeitschr. f. wiss. Zool. Bel. Ixvii. Taf. xiv. fig. 6. 



1 Loc. tit. Taf. xiv. fig. 6. 



