ON MEGASCOLEX CCERULEUS. 71 



give one tlie impression of an agency for distributing blood to 

 the lacuna-like vessels of the internal network^ as indeed^ I 

 believe, they are. 



The external network is formed by branches of the intestino- 

 tegumentary vessels. 



In the hinder region of the intestine precisely similar 

 arrangements obtain, but neither network is nearly so dense, 

 and the internal network quite loses its lacunar character. 



In the anterior region it is, owing to the pouches_, difficult 

 to make a flat preparation, and so to see these networks, but 

 from what I have seen I conclude that the differences between 

 the arrangements obtaining in this region and those above 

 described are only slight. 



Dorso-tegumentary Vessels (figs. 4 to 7, 9, d. t.). — 

 These are branches of the dorsal vessel connecting it with the 

 peripheral networks. In Lumbricus, according to Jaquet (6), 

 each divides into a " branche teguraentaire " and a " branche 

 dorso-sous-nervien,^' which latter is connected with the nephri- 

 dial capillaries. According to Perrier (9) a similar arrange- 

 ment obtains in Urochaeta, while in Pontodrilus, which is devoid 

 of a subneural vessel, the " branche dorso-sous-nervien " is 

 suppressed ; this is also the case in Megascolex. 



All the branches of the dorsal vessel anterior to the hearts, 

 and one pair of those branches in each segment posterior to 

 them, belong to this category. 



In the most anterior portion of the dorsal vessel they arise 

 from this latter slightly irregularly, i. e. unsymraetrically 

 (fig. 8). ^ 



In the region of the three pairs of lateral hearts and the 

 most anterior pair of latero-intestinal hearts there are no such 

 vessels. 



In the region of the four posterior pairs of latero-intestinal 

 hearts there are such branches, but I have no note as to their 

 exact place of origin. It may be some months before I obtain 

 any fresh material, and it is a point of such minor importance 

 that I leave it undetermined. 



In all other segments they arise, regularly, from the dorsal 



