486 EDWIN S. GOODRICH. 



off on eitlier side a branch passing downwards to spread over 

 the wall of the alimentary canal. 



The Dorsal Sinus. — Running along close to the wall of 

 the alimentary canal (figs. 1, 2, 4<, and 6) the dorsal sinus 

 gives off a pair of branches in each segment. One of these 

 loops underneath the anterior branch of the latero-dorsal 

 vessel in a peculiar manner (figs. 1 and 6). Both ultimately 

 break up into small capillaries passing into the cutaneous 

 plexus of the dorsal and dorso-lateral regions. 



Small sinuses also run ventrally from the dorsal sinus to the 

 wall of the alimentary canal, both to the crop and intestine, 

 although Gratiolet only found those supplying the latter (figs. 

 6 and 15). 



According to previous observers, the dorsal sinus communi- 

 cates with the ventral sinus in front and behind. 



The Ventral Sinus. — This large sinus, which contains 

 the nerve-cord, gives off two pairs of lateral branches in each 

 segment. The most important of these are the short canals 

 leading on either side into the perinephrostomial sinus, 

 entering at its anterior end. From the opposite extremity of the 

 sinus a branch is given off" to the nephridium (figs. 2, 3, and 5). 



In the region of the nerve ganglion a sinus branches out, 

 following the posterior lateral nerve for some distance (figs. 3 

 and 4). This sinus divides into two branches, one going to 

 the body-wall, in the ventral region, and the other passing 

 vertically upwards to the dorsal cutaneous plexus (fig. 4). 

 The latter is the abdomi no-dorsal of Duges. 



According to Gratiolet, a similar sinus passes up from the 

 perinephrostomial sinus ; but I have not been able to find it. 



A pair of vertical channels in each segment extend from the 

 ventral cutaneous plexus to the dorsal network. 



The chief point to notice about the systems of larger vessels 

 and sinuses is that the two do not communicate with each 

 other. It is only by means of the complex capillary systems 

 that the continuity is established. 



The Capillary Systems. — Gratiolet (4) divided the capil- 

 lary systems into three sections : (1) an inner deep layer, the 



