SPECIAL ANATOMY. 203 



foot. The pulmonary chamber occupies a position on 

 the outer side of the lower one to three whorls of the tur- 

 binated mass. The collar apparently takes the place of 

 the mantle in slugs. In all the genera it is attached 

 around the base of the turbinated mass, and is perfora- 

 ted on the right side by the pulmonary orifice. On the 

 outer border of the latter the anal aperture is placed. 



As in slugs, the genital orifice is situated on the right 

 side of the head, just posterior to the tentaculre. 



Chapter hi. — on the tegumentary covering of the 

 terrestrial gasteropoda. 



Besides a testa capable of enclosing the whole body, 

 which most of the terrestrial Gasteropoda possess, they 

 have a thick envelop, composed of mucous and muscular 

 membrane. The exterior, highly irritable and contractile 

 investment consists of an actively secreting mucous mem- 

 brane, (Figs. A, B, C, 1) with a substratum of interlaced 

 muscular fibres (2). In the naked genera it is prettj^ 



Figure A. 



Fig. a is a diagram representing the disposition of the coverings of 

 the body in Limax and Arion. 1. mucous lamina; 2. muscular subslratinn ; 

 3. muscular peritoneum ; 4. visceral cavity ; 5. rudimentury testa ; U. pul- 

 monary chamber. 



