HABITS AND FACULTIES. 195 
the Idmaeidce, whose means of protection, and whose 
chances of preservation are much less than those of the 
Rclicida', the number is much greater than in the latter. 
The number of eggs produced by two individuals of 
Umax agrestis kept in confinement by M. Leach, was 
in the course of rather more than a year seven hundred 
and eighty-sis. It usually amounts to at least three 
hundred per annum. The other species, though not 
equally prolific, multiply greatly ; and each pair of the va- 
rious species of Helicidce produce, annually, from thirty 
to one hundred eggs, and perhaps more. The young of 
the Llmacldce complete their growth and reproduce their 
kind sometimes within the year of their birth, and always 
as soon as the second year ; and the species of the 
other families are believed not to recpiire a much longer 
time to attain maturity. This rapid increase replaces 
the numbers annually destroyed, and maintains the spe- 
cies in their relative importance. 
Their extreme tenacity of life is manifested in every 
stage of growth, from the egg to the mature animal. The 
eggs ofLimaz have been so entirely desiccated that their 
form has disappeared, and there remained only a thin 
skin, friable between the fingers. In this condition they 
have been kept for years ; and yet a single hour's expos- 
ure to humidity was sufficient to restore their form and 
elasticity. 1 They have been dried in a furnace eight 
successive times, until they were reduced to an almost 
invisible minuteness, yet in every interval have regained 
1 Bouchard-Chantereaux, loc. cit. p. 15. 
