1 8 COMPARATIVE ANATOMY 



organs of the earthworm are invariably placed in definite 

 somites, it is of importance that the latter should be carefully 



.^—'^■ 







Fig. 3 



Luinbricus kercicleus, showing m, the mouth, situated on 

 the ventral surface behind the conical prostonnum ; 

 spth, spermathecal pores ; ov, oviducal pore on segment 

 14 ; s^d, spermiducal pore on segment 15 ; cl, clitellum 

 extending over segments 32 — 37 ; an, anus. 



counted and the positions of the more important organs and 

 external openings accurately noted. Beginning at the anterior 

 end of the body, it is usual to reckon the ring immediately 

 following the prostomium and partly encircling the mouth 



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