132 GROWTH OF SNAILS. 



reach them, and where moisture is constant. The num- 

 ber of these eggs does not appear to be very great. 



At the end of a time, varying more or less according 

 to the species, and probably, also, according to circum- 

 stances, the eggs open, and young snails come forth, 

 already covered with a shell, which is extremely thin. 

 They are, therefore, very much afraid of the drying 

 action of the air, and especially of that of the sun^ and 

 do not issue from the holes in which they have been 

 born, except during the night. They grow a good deal 

 at first, but afterwards much more slowly. 



The growth of the body of the snail requires a pro- 

 portional growth in the shell. The animal now remains 

 in a state of repose, sinks into some 1 cavity, and there 

 issues from all the parts of the mantle, and especially 

 from its thick edge, a stratum of matter, which is ap- 

 plied within the preceding, out-edging it a little. It is 

 this part of the junction of this new stratum which 

 forms the stria that marks the growth. It is so much 

 broader in proportion as the animal is better nourished, 

 and more vigorous. When the shell has reached its 

 utmost growth, it merely becomes thicker, and forms in 

 most of the species a sort of pad, more or less thick ; 

 and there is deposited on that part of the spire which 

 modifies the aperture, a calcareous matter, generally 



