96 Gaspard's Memoir on the 



in its glands or vessels the carbonate of lime in a free state, so that 

 when the surface of the collar is touched by any foreign body, at 

 each point of contact, a quantity of it is thrown out mixed with a 

 tenaceous mucilage. To be still further convinced of the fact, I 

 cutoflFthe collar of the mantle, and having thrown it into a dilute 

 acid, a quantity of gas was given ofi', and the liquid gave the 

 usual white precipitate with the addition of soda. No other struc- 

 ture similarly treated afforded the same results. 



It is not therefore surprising that the collar of this snail should 

 be so plump and white in autumn previous to the hibernation, and 

 so lean and grey when it makes its appearance in April, or when 

 the operculum is taken off in the intermediate time. The animal 

 derives this calcareous fluid not merely from its ordinary vegetable 

 food, but chiefly from the earth wtiich it eats in great abundance, 

 by means of which the necessary quantity of lime is kept up, and 

 its loss repaired with facility. On this account we see these snails 

 when deprived of nourishment unable to form any thing more than 

 mere membranous substitutes for the former calcareous opercula 

 which had been removed.* 



tie is the organ which ordinarily performs this function. I have at different 

 times cracked the shell, removed small portions, and drilled holes through it, at 

 different parts, and I have found that if the injury were within the reach of the edge 

 of the mantle, it was always drawn up to repair it. I will particularize one only 

 of these experiments to shew the manner in which this is done. I drilled a hole 

 in the shell of Helix pomatia in the last whorl but one, thinking that it could 

 not draw the edge of the mantle high enough to repair it in the usual way ; 

 however it effected this immediately by protruding the foot to make room for 

 the mantle being drawn high up into the shell, and as soon as the edge came in 

 contact with the injured part, it was passed repeatedly over the hole, leaving 

 a layerofcalcareousmatter each time until it became opaque; and in a day or two, 

 on examining it, I found the newly formed part apparently as strong as therestof 

 the shell. Another curious circumstance connected with this subject, is, that in 

 the species of snails with coloured bands, H. nemoralis for instance, there are 

 the same number of bands on the mantle as in the shell ; which are brown and 

 transparent, and these probably contain comparatively little carbonate of lime. 

 It is therefore not unlikely that the glands necessary for secreting this substance, 

 do not exist, at least to an equal degree, in those parts of the mantle marked by 

 the bands. This, however, is but a conjecture, and only important as connected 

 with a subject which deserves a much more accurate investigation than has 

 ever yet been bestowed upon it. T. B. 



* These circumstances may account for //. pomatia thriving more, and being 



