THE ANATOMY. REPRODUCTIVE SYSTEM 



85 



arranged parts. The sperm-sacs, too, though often ranged with an absolute regularity, 

 sometimes show the same kind of divergence from what we must consider to be the 

 normal for a segmented worm. 



Plates I and II represent the genitalia of various Oligochaeta depicted diagram- 

 matically. 



i. Gonads. 



The gonads are developed from the peritoneal epithelium and are nearly always 

 paired structures, probably they are really paired in origin in such forms as Aeolosoma 

 where they appear to be single. Both male and female gonads are present in all 

 Oligochaeta ; there is no instance known of an unisexual form. The ovaries are most 

 usually a single pair but there are sometimes an additional pair; no more than two 

 pairs of ovaries have ever been certainly made out 1 . The ovaries invariably agree 

 in position with the testes, but they are of course situated in different segments ; 



1 Except in abnormal specimens such as those described by WOODWARD (1, 2). 



