10. 



15. 



A an 



mu 



B ac— / ^ w m ~ ^ an 



Fig. 137. — Structure of the earthworm. 



A, ventral view of anterior and posterior ends. B, diagram showing a seta and muscles 

 by which it is directed anteriorly and posteriorly, and protruded (cf. retractor muscle of 

 setiE shown as s.m. in Fig. 140). C, internal organs in anterior portion of body as dissected 

 from dorsal side. The nephridia are not shown {cf. Fig. 143, D). D, schematic longitu- 

 dinal section showing body wall, digestive tract, coelome, and septa. 



an, anus; br, brain; c, clitellum; e.g., calciferous glands; cr, crop; d.b.v., dorsal blood 

 vessel; e, esophagus; g, gizzard; h, heart; m, mouth; mu, muscle fiber; n.c, ventral 

 nerve cord; od, opening of oviduct; ph, pharynx; ps, prostomium; r.m., radial muscles 

 of pharynx; s, septum; se, seta; s.g., seminal groove; s.i., stomach-intestine; sn.v., sub- 

 neural blood vessel; s.r., seminal receptacles; s.v.l. s.v.2, s.v.3, seminal vesicles; v.b.o., 

 ventral blood vessel; v.d., vas deferens; w, body wall. (From Sedgwick and Wilson 

 "General Biology," copyright, 1914, by Henry Holt and Co., reprinted by permission.) 



284 



