CHAPTER IX 



THE EARTHWORM AND ITS ALLIES 



Relationships. : Earth worms 1 belong to an order of 

 Annelids known as Oligochieta. 2 This group is distin- 

 guished by a prevailingly non-marine life, by the absence 

 of parapodia, by few bristles, and by the absence of tenta- 

 cles, palps, cirri, and gills. 3 



Habits. Earthworms, as the name implies, are inhabit- 

 ants of the ground, through which they burrow and in 



FIG. 122. Flash-light photograph of earthworm and slug crawling on a pave- 

 ment at night. Photo, by D. and S. 



1 There are not very many kinds of terrestrial Oligochseta. The prin- 

 cipal American species may be distinguished with the aid of the key given 

 in the Appendix to this Chapter. 



2 (JXfyos, few ; x a ^ T7 7: hair. 



8 The Oligochreta exhibit two principal subdivisions ; the first of which 

 includes terrestrial species of the single family Lumbricidae, and the 

 second various aquatic families, a key to which is given on page 144. 



