12 



THE EARTHWORM; Lumhricus terrestris. 



Observe in a living earthworm the natural movements, and the rows of setae 

 which subserve locomotion — ^the four rows of setse are easily detected by carrying 

 the finger along the ventral surface from behind forwards ; the dark dorsal and pale 

 ventral surface and the iridescent cuticle ; the clitellum ; the small retractile lobe 

 (prostomium) in front of the mouth and the numerous rings (somites) between the 

 mouth and the terminal anal segment. 



A, Make a sketch (2 nat. size) of the dorsal surface of the first 40 or 50 



segments showing — 

 (a) The prostomium. 



(6) The enlarged segments (29 to 36 inclusive) which form the clitellum. 

 (c) The dorsal vessel (if visible) running along the median line and the 

 position of the single row of minute dorsal pores. 



B. Make a similar sketch of the ventral surface showing — 



(a) The mouth between the prostomium and the 1st segment. 



(b) The 8 setse in each segment (except 1st, 2d, 3d, and last) — 2 ventral 



and 2 lateral on each side of the median line . 



(c) The clitellum. 



(d) The thickening of the epidermis in the region of the inner setiger- 



ous glands (8th to 11th segments). 



(e) The 4 apertures of the spermathecae — two on each side — ^between the 



9th and 10th and 10th and 11th segments. 

 (/) The genital openings between the ventral and lateral setse, (1) of the 



2 oviducts in the 14th segment and (2) of the vasa deferentia in 



the 15th segment. 

 (g) The openings of the segmental organs (nephridia), some internal 



and others external, to the ventral setse, — ^nephridia absent from 



1st and 2d segments. 



