ASCAKIS. 



the hind-end of the male is shghtly coiled, and has a pair of 

 minute bristles or anal se/ce protruding from the 

 anal aperture. The body is of a whitish 

 colour, and it has four lines (a dorsal and 



ventral and two lateral) along its surface. 



External 

 Features. 



Fig. Sy. — Diagrammatic Transverse Section of Ascaris 

 Megalocephala. {Ad 7iat.) 



Dorsal Nerve Cord. 



Excretory 

 Duct, 



Oviduct, 



Uterus. 



Ventral Nerve Cord. 



The mouth is at the anterior end, surrounded by a dorsal 

 and two lateral lips which bear sense-papillae, probably 

 tactile. The anus is a little distance from the posterior end 

 on the ventral surface. Some little way behind the mouth 

 is a minute median ventral pore, the excretory opening. 

 On dissection we find a definite body-cavity* in which 

 lie freely the alimentary and reproductive organs. The 

 mouth leads into a pharynx with muscular walls lined by 

 chitin. The suctorial pharynx opens into a long intestine ^ 

 terminating in the anus. The intestinal epithelium is said^^ 

 to secrete on both surfaces a delicate cuticle, 



* This cavity may be a modified coelom or may be an archiccele : the structlu^ -n a 

 of the excretory organs points to the latter. , jf x ^ 4 



