22 EARTHWORMS AND THEIR ALLIES [ch. 



ovaries in segment xiii. The sperm ducts open on 

 to the exterior in the position already mentioned and 

 they are not associated at their pore with any glands 

 comparable to spermiducal glands. A pair of sperm 

 sacs depend from segment xi and traverse a consider- 

 able number of segments, being thus long and 

 tongue-shaped instead of short and limited to one 

 segment. The spermathecae are three pairs of 

 elongated sacs in segments vii-ix, without any 

 diverticula at all. 



It will appear therefore that many and consider- 

 able differences divide Pontoscolex from Notiodrilus 

 and indeed from all of the Megascolecidae whose 

 structure has been touched upon in the foregoing 

 pages. The most important of these are the orna- 

 mented setae and their arrangement and the modi- 

 fication of the setae upon the clitellum : the absence 

 of diverticula to the spermathecae: the absence of 

 terminal glands associated with the male ducts. 

 Although taken in their entirety these characters are 

 distinctive of the American Geoscolecidae (sub-family 

 Geoscolecinae), there is no one of them which is not 

 to be found in some Megascolecid. Thus the sub- 

 genus Ilyogenia (of Ooierodrilus) has sometimes no 

 spermiducal glands : the genus Perionyx has sperma- 

 thecae without diverticula in some species, and other 

 genera of Megascolecinae are in a like condition. 

 The setae of Dichogaster are sometimes ornamented, 



