252 W. S. NiCKEHSOK, 



the body whicli does not contain the ovary. The sexual amphitypy 

 which Staffoed flnds in C. americanus I have not observed in 

 C. vesicaudus. 21 specimens examined with respect to tliis factor 

 showed the ovary in every case on the rig-ht side and the anterior 

 testis on the left side. If it occurs at all it is certainly much less 

 common than in his form. 



The ova of C. vesicaudus measure 38 — 40X17 — 21 fi. 



The excretory System is the one which presents the most in- 

 teresting conditions. In its main features it agrees with the de- 

 scriptions of Poirier and Staffoed but differs from the Systems 

 which they described in the possession of a rounded Chamber inter- 

 posed between the excretory vesicle and the excretory pore which 

 they neither mention nor flgure and which is unlike any structnre 

 which I have seen described in other trematodes. I shall refer to 

 this as the caudal vesicle. It was with reference to this unique 

 morphological feature that the name vesicaudus was chosen. The 

 extent of the excretory vesicle is shown in Fig. 6. Its main stem 

 is formed by the union of two chief branches which beg-in far 

 forward beside the oral sucker and extend backward near the 

 lateral margins of the body to the region of the testes. In this 

 part of their course they receive from both sides numerous short 

 dendritic branches. Near the testes they bend sharply inward and 

 meet in the niiddle line back of the posterior testis to form the 

 main trunk of the System which extends directly back to open into 

 the pecnliar rounded Chamber already mentioned. This main stem 

 also receives about 3 pairs of lateral branches whose dendrites 

 extend out to near the lateral and posterior margins of the body. 

 The larger branches of this System are of about the same caliber 

 as the intestinal coeca as shown in Fig. 2. They are lined thruout 

 by an irregularly columnar epithelium which is low in the smaller 

 branches and correspondiugly higher in the larger ones. In the 

 latter the distal parts of the cells stand up independently of one 

 another in a manner suggesting an amoeboid activity during life. 



The relations of the terminal portion of the excretory vesicle, 

 the caudal vesicle and the excretory pore are shown in Figs. 3, 4, 

 ö, 6 and 7. Figs. 3 and 4 are adjacent sections from a transverse 

 series. Owing to the strong ventral flexure of the caudal portion 

 of the worm however the sections in the latter part of the series 

 from which these came are made to run obliquely ventrad and 

 caudad as indicated in the small sketch Fig. 8 x — y. Fig. 3 shows 



