II] MODE OF LIFE 53 



Clitellio arenarius and Tubifex ater (not uncommon 

 on British shores), marine LumbricuHds and a marine 

 Naid from the Italian coast. These forms show no 

 great differences from their fresh-water allies. 



Earthworms originally purely aquatic 



ANIMALS. 



The very name Earthworm, so distinctive as it is 

 of the habitat of these animals, seems to have been 

 expressly invented in order to crystallise into one 

 word the remarkable distributions of these creatures. 

 They are with very few exceptions the most purely 

 terrestrial animals that we know. There are a few 

 Mammals like the mole and several underground 

 Amphibians and Snakes in the tropics which share 

 this habitat with the worms, probably because they 

 chiefly prey upon them. But there is no group of 

 animals that is characterised by a subterranean 

 existence in the way that earthworms are. For Me 

 cannot put burrowing animals, such as the prairie 

 dog and many rodents, into the same category. 

 These make and seek their burrows for i)rotective 

 purposes and in order to bring forth their young in 

 security. They do not feed beneath the surface of 

 the ground or pass their entire lives in that situation. 

 We have already in a previous chapter dealt with 

 such exceptional forms of earthworms as do not lead 



