462 ALFEED GIBBS BOURNE. 



surface and open into the anterior extremity of the ventral 

 vessel. 



In the region of the pharynx the dorsal vessel gives ofiP 

 a small trunk which branches upon the walls of this organ 

 in a manner accurately described by Budge. The branches 

 collect again into a vessel which opens into the ventral 

 vessel. 



The 2nd, 3rd, and 4th of the dilatations above mentioned 

 give off branches, the anterior of which run forward directly 

 and open into the anterior extremity of the ventral vessel, 

 the posterior run backwards for a considerable distance, as far 

 as the thirteenth post-oral ganglion and then run forwards 

 to open on each side into the ventral vessel close to its anterior 

 extremity. 



At its posterior extremity the dorsal vessel gives a series of 

 vessels on each side (four, according to Budge, six, according to 

 Whitman), which looping round on to the ventral surface give 

 rise to the ventral vessel. 



Ventral Vessel. — This lies with the nerve-cords, ovaries, 

 and nephridial funnels in the ventral sinus (woodcut, fig. 3, and 

 fig. 64, v.v). It is formed anteriorly by the branches of the 

 dorsal vessel above mentioned, receives the efferent pharyngeal 

 vessel and posteriorly, anastomoses with the dorsal vessel as 

 shown above. I may point out in passing, how closely this 

 system of vessels resembles that of Braachiobdella. In addition 

 to the vessels and sinuses described above there are certain 

 other blood spaces, the exact relations of which I have been 

 unable to make out: — 



1. Budge describes other branches of the dorsal vessel (nine 

 pairs) which supply the walls of the gastro-ileal portion of the 

 alimentary canal, and after anastomosing with one another open 

 at three spots on each side into the lateral sinus. I cannot 

 speak positively regarding these branches, of which Whitman 

 makes no mention. My sections show that such branches exist, 

 but I cannot trace their distribution, and I have not had an oppor- 

 tunity of examining the transparent species, C. bioculata, 

 used by Budge; that they supply the intestinal walls is probable 



