490 EDWIN S. GOODRICH. 



the inner side of the botryoidal tissue its vessels open here and 

 there into the small sinuses passing outwards to the interme- 

 diate layer. 



In the ventral region the botryoidal channels also open 

 directly into the perinephrostomial sinus (fig. 17). 



I must finally describe the communications between the 

 contractile and non-contractile systems which occur in connec- 

 tion with the vascular supply of the alimentary canal. ^ 



Gratiolet gave a correct description of the vessels of the in- 

 testine. They are derived from short vertical branches coming 

 off from the latero-dorsal arches, and passing into a longitudinal 

 lateral vessel on each side, which is itself connected with a 

 median ventral channel. From these lateral intestinal vessels 

 a fine plexus of capillaries extends over the wall of the alimen- 

 tary canal ; joining again into larger trunks, the capillaries 

 open at intervals into the dorsal sinus (such a connection is 

 shown in the reconstruction given in fig. 15). 



It may be added that a similar communication exists on the 

 wall of the crop, but the capillary plexus is there less elaborate 

 (fig. 6). 



I have also noticed a peculiar connection between the latero- 

 abdominal vessel and the abdomino-dorsal sinus by means of a 

 tortuous capillary shown in fig. 4 at C. This may be excep- 

 tional. 



Summary and Conclusion. 



According to the foregoing account, the evidence of carefully 

 executed injections strongly favours the view that a continuity 

 exists between the contractile vascular system and the non- 

 contractile sinus system in Hirudo. This continuity is proved 

 to exist in various regions of the body by means of serial 

 sections. The communication takes place through the capillary 

 systems. 



The hsemolymph system of Hirudo consists of four main 

 longitudinal trunks, sending out transverse branches to the 



• I have no doubt a similar continuity exists on the walls of the nephridium, 

 as mentioned by Gratiolet. 



