208 



MANUAL OF ZOOLOGY 



the anterior and posterior ends of the body. They send off 

 branches both dorsally and ventrally, some of which anasto- 

 mose with one another. The ultimate branches break up 

 into capillaries in the integument, nephridia, etc. 



The two principal sinuses are respectively dorsal (d. s) and 

 ventral (v. s), the former lying just above the enteric canal 

 in the middle dorsal line, the latter occupying a similar 



Fig. 120. — Nephridium of the medicinal leech, a. I, apical lobe; m. I, middle lobe; 

 n. p, nephridiopores; nst, nephrostome; r. I, recurrent lobe; t. I, testis lobe; 

 vs, vesicle ; vs. d, vesicle duct. (After Bourne.) 



position on the ventral side, and enclosing the ventral 

 nerve-cord. 



The nervous system is of the usual annulate type. There 

 is a small brain (Fig. 119, br) situated above the anterior 

 end of the pharynx immediately behind the median dorsal 



