XV111 INTRODUCTION. 



variegated snail (Helioc nemoralis). It is a com- 

 mon inhabitant of our woods, and gardens, and may 

 therefore be easily brought forward as an evidence 

 at any time. The ground of this shell is white, ci- 

 tron, or yellow, or of an intermediate colour. It 

 is marked with streaks, or bands, which proceed from 

 the apex to the mouth of the shell, and are either 

 black, brown, or red. They vary in number ; some 

 shells have but one, others have four, and some are 

 ornamented with five or six bands. 



We have already observed, as a position which 

 does not admit of a doubt, that all univalve shells 

 enlarge by the mouth, in consequence of a secretion, 

 emitted for that purpose, from the collar of the ani- 

 mal. Reaumur reckons it sufficient for this collar 

 to be composed of glands filtering different hu- 

 mours, to form a shell of different colours. If, for 

 example, two or three glands secrete a black, or 

 brown humour, and these glands, which Reaumur 

 calls Jiltres, are parallel to each other, while the 

 rest of the collar emits only a uniform citron tint, 

 it follows that the ground of the shell should be 

 straw colour, with parallel bands of black or brown, 

 approaching or receding from each other, in pro- 

 portion as the space between the glands is greater 

 or less. 



If we could bring no proof of the above con- 



