STRUCTURE OP THE EARTHWORM. 



193 



of the nerve cord, another (infra-neural) along the under 

 surface, while two small lateral-neurals pass along each side 

 of this same cord. All these longitudinal vessels, of which 

 the first three are most important, are parallel with one 

 another ; the first three meet in an anterior network on the 

 pharynx ; the dorsal and the supra-neural are linked together 

 in the region of the gullet by five or six pairs of contractile 

 vessels or "hearts." The precise path of the blood is not 



Fig. 61. — Transverse section of Earthworm. 

 (After CLAPARfeDE.) 



c, Cuticle ; e., epidermis: cm., circular muscles; I.m., longi- 

 tudinal muscles ; j.,aseta; cce., coelome ; jj/.,;., yellow cells ; 7'., 

 typhlosole; v.'j., ventral blood vessel; s.n.v., sub-neural vessel 

 below nerve cord ; d.v., dorsal vessel. 



known, but the distribution of vessels to skin, nephridia, 

 and alimentary canal is readily seen. 



Respiration is effected by the distribution of blood on the 

 general surface of the skin. 



13 



