A LAND SNAIL loi 



the penis. This organ has already been noted ; it is tubular in 

 shape and lies in a bent position across the oesophagus. A re- 

 fractor muscle inserted at the bend connects it with the dorsal 

 body wall. At the point where the vas deferens meets it observe 

 the flagellum, a long, tubular sac into which spermatozoa pass 

 from the vas deferens and where they are massed together to form 

 spermatophores. Both penis and vagina communicate, side by 

 side, with the genital cloaca, which opens to the exterior through 

 the common genital pore. 



When two animals pair each receives a spermatophore from 

 the other. This passes into the receptaculum seminis, which is 

 thus filled with the spermatozoa of the other animal, and these 

 finally fertilize the eggs as they pass into the vagina from the 

 oviduct. 



Exercise 7. Make a semidiagrammatic drawing of the reproductive 

 organs on a scale of 2. 



Split the dart sac and take out the dart ; mount it on a slide 

 in water or in glycerine and examine it under a compound 

 microscope. 



Exercise 8, Draw the dart. 



The Nervous System. Sever the oesophagus and remove the 

 reproductive and digestive systems, leaving the pharynx in the 

 body and taking care not to injure any of the nerves. The prin- 

 cipal ganglia are contained in the nerve collar. The two supra- 

 oesophageal ganglia, which constitute the brain, will be seen 

 joined by a broad transverse commissure. From their anterior 

 surface nerves run to the tentacles, and from their inner surface 

 a pair of nerves run to the posterior end of the pharynx, where 

 they meet a pair of small phar5mgeal ganglia. The supraoesophag- 

 eal ganglia are connected by broad connectives with the sub- 

 oesophageal ganglia. Remove the pharynx from the body. By 

 slightly scraping the suboesophageal ganglia with a small scalpel, 

 it will be seen to consist of two principal ganglionic masses. The 

 forward mass is a pair of ganglia, the pedal ganglia ; the hinder 

 mass consists of the large visceral ganglia, at the side of which is 



