298 



MANUAL OF ELEMENTARY ZOOLOGY 



stomodseum, or fore-gut, known as the pharynx, a long mid- 

 gut, and a short proctodeum, or hind-gut, known as the 

 rectum. The fore- and hind-guts are lined by inturned 

 ectoderm, with a prolongation of the outer cuticle, which is 



egg 



vl. 



Fig. 205. — A transverse section through the middle 6f the body 

 of a female Ascaris lumbricoides. 

 cu., Cuticle ; d.l., dorsal line ; d.n., dorsal nerve ; cct., ectoderm"; egx\ end., endo- 

 derm; ex.c, excretory canal; int., intestine; /./., lateral line; m.f. muscle 

 fibre; «»., ovary; p.c, perivisceral cavity; ut., uterus; ».<., ventral line; 

 v.n., ventral nerve. 



shed with the latter. They have in their walls muscular 

 fibres. The mid-gut is composed solely of a layer of 

 columnar epithelium, with a very delicate cuticle within 

 and without. The food consists of solids and liquids 

 taken up from the contents of the intestine of the host. 

 There is no vascular or respiratory system (see p. 309). 



