V CLASSIFICATION 341 



phyla. The earthworm is a member of the phylum 

 Annulata, which also includes a number of other worms living 

 in the sea and in fresh-water, as well as the leeches, &c. In 

 all these the body is elongated and divided into metameres; 

 there is usually an extensive coelome ; and the nervous 

 system and nephridia are similar to those of the earthworm. 

 The class Chcetopoda, in which the earthworms and their 

 fresh-water and marine allies are included, receives its name 

 from the fact that all its members are provided with cuticular 

 setae, which in the order to which the marine forms belong 

 {Polychata) are usually long, and of varied forms, and are much 

 more numerous than in the earthworms and fresh-water 

 worms, which constitute the order Oligochmta. This order 

 includes several families, both Lumbricus and Allolobophora 

 belonging to the family Lumbricida. 



PRACTICAL DIRECTIONS. 



EARTHWORM. 



Select a large earthworm, and after noting its movements and 

 mode of progression, kill by immersion in spirit for a few minutes and 

 then place in a dish and let the tap run on it for a short time. 



A. External Characters :— 



1. Note : — a. The form and colour of the body and its division into 

 metameres ; b. the anterior end terminating in the prostomium and fol- 

 lowed by the peristomium ; c. the clitellum ; and d. the last or anal 

 segment. 



2. If the worm be drawn through the fingers backwards, the seta 

 will be felt : examine with a lens and observe their position and the 

 number in each segment. 



3. Make out the following apertures : a. the mouth ; b. the anas ; 

 i. the dorsal pores (p. 325) ; d. the two apertures of the spermiducts, 

 with thickened lips, on the fifteenth segment. 



(It requires careful examination to see the other apertures, viz, — 

 those of the oviducts, spermothecce, and nephridia). 

 Sketch from below or from the side, 



