118 THE SNAIL 



5. The male duct and its accessory organs. 



a. The vas deferens is a slender, slightly convoluted 



tube of uniform diameter, which runs forwards 

 along the inner side of the female organs, between 

 these and the buccal mass, passes under the 

 retractor muscle of the right upper tentacle, and 

 then runs back to open into the base of the penis. 



b. The flagellum is a long tubular diverticulum, which 



arises from the vas deferens just before it reaches 

 the penis. It lies along the dorsal surface of the 

 crop and other viscera. In it the spermatozoa 

 are agglutinated together to form a long rod-like 

 body, the spermatophore. 



c. The penis is a muscular tube continuous with the 



vas deferens, and lying somewhat obliquely across 

 the oesophagus just behind the buccal mass ; it 

 opens to the exterior at the genital pore, through 

 which it can be protruded. 



To the penis is attached the retractor penis 

 muscle, a narrow muscular band, which arises 

 from the floor of the mantle-cavity, and runs 

 downwards and forwards to its insertion. 



6 The female duct and its accessory organs. 



a. The oviduct is a short thick-walled tube, running 



forwards from the point at which it leaves the vas 

 deferens. 



b. The vagina is a thick-walled tube into which the 



oviduct opens behind, and which runs forwards 

 to open with the penis at the common genital 

 pore. 



c. The mucous glands are two tufts of tubular glands, 



opening by a pair of apertures into the vagina : 

 each tuft consists of thirty to forty finger-like 

 processes. 



d. The dart sac is a large pyriform sac opening into 



the vagina just beyond the mucous glands. It 



