208 HENRY LESLIE OSBORN 



merely a passage and not a place of storage and that the collect- 

 ing vessel is the functional bladder. 



The collecting vessels are very large in the posterior region of 

 the body, but anteriorly their identity is lost. It is usual in trema- 

 todes for a collecting vessel to run from the terminal bladders for- 

 ward to a point near the anterior end of the body and then to 

 bend suddenly on itself and run backward again. The second 

 vessel, called the recurrent vessel, is supplied with a strong vibratile 

 apparatus, while the collecting vessel lacks these. In Chnosto- 

 mum the collecting vessel is readily traced forward as far as the 

 ventral sucker. In fig. 2 it is shown on the right side omitted on 

 the left, in fig. 3 it is shown as far forward as the genital organs 

 and then omitted, in fig. 4 it is shown in sections B-G. It disap- 

 pears a short distance in front of section number 150. The level 

 of the vessel is seen from the cross-sections. It always lies exter- 

 nally to the caeca and generally slightly ventrally. Its diameter 

 is quite variable as in fig. 15, a camera drawing of a section pass- 

 ing in its plane for a long distance. The wall is epithehal and 

 muscular. 



I am not able to give a definite account of the relation between 

 the collecting vessel and the recurrent vessel. I have devoted 

 much time to the study of this in different ways without being able 

 to follow the collecting vessel forward to where it meets the recur- 

 rent vessel. The body is too thick anteriorly to allow this point 

 to be seen in an entire compressed specimen. I have repeatedly 

 examined the youngest individuals I could find but without suc- 

 cess. The network of anastomosing vessels (described in a mo- 

 ment) are so complicated in the anterior of the body that it is 

 impossible to recognize the collecting vessel if, indeed, it has re- 

 mained distinct from them. It is, of course, possible that the 

 collecting vessel does not remain distinct but is lost in the network 

 of vessels. 



Allusion was made above to the system of cavities which lie in 



the body wall immediately under the cuticle. In Hving worms 



just removed from bass cysts these cavities are filled with a 



cream-colored fluid composed of minute highly refractive drop- 



ets which has the effect of an injection, making it very easy 



