18 EARTHWORMS AND THEIR ALLIES [ch. 



glands are reduced to a single pair or to a single 

 gland in the ixth segment, the nephridia though 

 regular and paired have no covering plexus of 

 blood vessels, and the worms themselves are slender 

 and delicate, being indeed often aquatic in habit. 

 The spermiducal glands, which are as in the former 

 sub-families independent of the sperm ducts though 

 sometimes opening in common with them into a short 

 pocket-like ingrowth of the skin, are reduced in their 

 minute structure and much simpler than in the other 

 types. 



The genus Kerria is the least reduced perhaps. 

 It has the male pores on segment xviii with a pair 

 of spermiducal glands on the segments preceding 

 and following this in the typical Acanthodriline 

 fashion. There are two pairs of spermathecae in viii 

 and IX, but the spermaries are reduced to one pair 

 in X. The gizzard is present. Ocnerodrilus is a 

 little further reduced from this last. The gizzard 

 has gone ; there is but one pair of spermiducal glands 

 (as a rule) opening in common with the extremity of 

 the male duct on to segment xvii ; the spermathecae 

 also are reduced to one pair, but there are two pairs 

 of spermaries. The African Nannodrilus is more 

 robustly built. There are two gizzards, the male 

 duct opens into a muscular pouch, into which also 

 open one of the two or three pairs of spermiducal 

 glands. There are two or three other genera and 



