NEPHRIDIA OF LEECH 



277 



Excretory system. — There are seventeen pairs of 

 excretory tubules or nephridia, from the second to the 

 eighteenth segment inclusive. These open laterally on the 

 ventral surface, voiding the waste products extracted from 

 the blood vessels which cover their walls. From the 

 seventh to the seventeenth, each nephridium ends internally 

 in a cihated " cauliflower lobe," corresponding to the funnel 

 of Oligochteta, and enclosed in a blood space, apparently 



Fig. 150. — A nephridium of leech. — After Bourne. 



F., Internal terminal funnel ; C, glandular coil covered with blood 

 vessels ; T^., external terminal vesicle. 



part of the reduced ccelom. In the first nine of these 

 funnel-bearing nephridia the terminal lobe lies close upon 

 and dorsal to a testis, but there is no morphological 

 meaning in this approximation. Each consists of two 

 parts, a twisted horseshoe-shaped glandular region, where 

 the actual excretory function is discharged, and a spherical, 

 internally ciliated bladder opening to the exterior. Within 

 the latter there is a whitish fluid with waste crystals. 



Reproductive system. — The leech, like many other 

 Invertebrates, is hermaphrodite, containing both male and 



