,IV 



LUMBRICUS 



131 



to strip off when the dead worm has been for some time submerged 

 under water in the dissecting dish. Projecting slightly from the 

 surface of the body are minute stiff bristles or chaetae. Of these 

 there are in each somite eighty arranged in four pairs in a transverse 

 row round the ventral half of the segment. They are most easily 

 detected in the posterior flattened portion of the body and may be felt 



cLv. 

 am. 



ty. 



Cnv. 



l.m. 



n. 



K 



i/.u 



Fig. 63. 



Lumbricus, transverse section about the middle of thie body, am, Amoebocytes ; cm, .circular 

 muscles ; coel, coelome ; d.v, dorsal blood-vessel ; ec, epidermis ; eTtd, endoderm ; int, intestine ; 

 l.m, longitudinal muscles ; N, ventral nerve-cord ; «, nephridimn ; ty, typhlosole ; v.v, ventral 

 vessel ; yx, yellow cells. 



[The cavities of blood-vessels are shewn in black.] 



by a sensitive finger passed along the surface of the body, or seen with 

 the aid of a lens. 



At the front end of the earthworm is the wide mouth opening 

 (Fig. 62, M), overhung by a fleshy projecting lobe — the prestomium (Ps). 

 At the extreme posterior end of the body is a vertical slit — ^the anus ( A) 

 or posterior opening of the alimentary canal. 



Finally, if the worm be sexually mature, a distinct pale coloured 

 and somewhat saddle-shaped swelling (Fig. 62, CI) is seen encircling the 



