CONTRIBUTIONS TO THE ANATOMY OF THE HIRUDINEA. 469 



These dilatations, says Gratiolet, do not exist in connection 

 with the nephridia anterior to the first testis, but behind this 

 point all the nephridia have them, and depending upon or rather 

 determining this arrangement is the fact that the four 

 anterior nephridia do not possess funnels, while the others 

 do, even the two which are placed behind the testicular region. 



These "perinephrostomial sinuses," as I propose to call them, 

 which are in Hirudo merely special developments of the cir- 

 curatesticular sinuses of Poutobdella (see p. 456) are severally 

 in direct communication by means of a short vessel with the 

 ventral sinus, also from each passes a vessel which ascending, 

 ramifies among the dorsal networks, the cardio-dorsal 

 branch of Gratiolet. 



In addition to these arise the capillary networks upon the 

 testicular walls. These networks represent in fact a circum- 

 testicular sinus which has become reduced by diacoelosis (wood- 

 cut, fig. 4, ie.). 



The capillary networks upon the testicular walls are con- 

 nected with the botr^-oidal and other networks in the ventral 

 region. 



The Ventral Sinus. — The ventral sinus was first recog- 

 nised as a blood space containing the nerve-cords by Johnson.^ 

 In the region .of the nerve-ganglia sinuses are connected with 

 the ventral sinus on either side ; these are connected with the 

 capillary networks of the dorsal region; they necessarily pass 

 close to the walls of the crop. In the gastro-ileal region these 

 pass with the cardio-dorsal trunks at the sides of the intestine 

 between this and the last pair of csecal dilatations of the crop. 

 They have been termed by Duges abdomino-dorsal branches 

 (sinuses, A. G. B.). These, together with the cardio-dorsal 

 trunks and the short vessels of Brandt, which occur in the 

 interval between two pairs of the abdomino-dorsal sinuses, 

 like the vertical superficial branches, connect the dorsal and 

 ventral networks. Thus the three systems of dorso-ventral 

 trunks are the sole origin of the vascular supply of the 

 walls of the crop, this latter representing the primitive peri- 



' A Treatise on the MediciDal Leech,' 1816, p. 115. 



