THE EARTHWORM 31 



epidermis of the clitellum is made up of several layers of 

 glandular cells. 



The sacs in which the chaetae are implanted are invagina- 



Fig. 7 



A transverse section through the intestinal region of Litmbricus hcrculcus magnified. 

 Ch, ch, chsetae ; dr. m, layer of circular muscles ; clg, chloragogen cells ; cu, 

 cuticle ; d.p, dorsal pore ; ep, epidermis ; z", intestine ; /.?/;, longitudinal 

 muscles ; nc, nerve cord ; nph t nephridium ; sb, sub-intestinal blood-vessel, 

 below it are the sub-neural and lateral neural vessels attached to the nerve cord ; 

 sp, supra-intestinal b'ocd-vessel ; ty, typhlosole. 



tions of the epidermis. The cuticle forms a lining to the sac 

 for a certain distance : beyond this the chaeta ends in a mass of 

 cells, each one of which can produce a new chaeta to replace 

 the old one. Beneath the epidermis is a layer of circular 

 muscle fibres embedded in a granular nucleated substance. 

 The individual muscle fibres are elongate, pointed at both 

 ends, and longitudinally striated. 



