II] MODE OF LIFE 47 



are one of the only division^ of the Oligochaeta 

 terricolae which are generally found to be without 

 those characteristic series of pores in the middle line 

 of the back known as the dorsal pores. They are 

 thus eminently suited for an aquatic life ; for it is to 

 be supposed from the fact that the purely aquatic 

 ' Limicolae ' are also without these pores that their 

 existence is prejudicial to a water-living worm. 

 Indeed the entrance of water into the body-cavity 

 would presumably be dangerous to the worm. The 

 Geoscolecidae are thus already marked out, as it 

 were, for an aquatic life. No modification is here 

 necessary for them. It is also to be noted in this 

 connection that various species of the genus Notlodri- 

 lus to which reference has been made as a partly 

 aquatic genus have no dorsal pores. They too are 

 thus fitted for at least an amphibious life. 



The rule however regarding the absence of dorsal 

 pores in the Geoscolecidae is not absolute. A few 

 species and among them two species at any rate of 

 the aquatic genus Spargauophilm have a few pores 

 between some of the anterior segments which have 

 been spoken of as 'neck pores.' They are not, it is 

 to be believed, of a diflferent nature from the generally 

 distributed dorsal pores of other worms but are in 

 fact limited to the * neck ' region. 



There are no other obvious characters of the 



1 In the Eudrilidae also these pores are very frequently absent. 



