252 ANIMAL REPRODUCTIONS. 
ject to the influence of the air: thus it will cicae 
trife ; and the contraétion, occafioned by the ci- 
ceatrice, will prevent the reproducing germ from 
breaking through and expanding. The mutilations 
of fnails, hitherto mentioned, were for the moft - 
part performed when fpring was fomewhat ad- 
vanced ; becaufe I had obferved, that no lefs 
than 61° of heat was neceflary to obtain repro- 
duction, which we generally have not in Lom-— 
bardy before that time; and if they are then 
decapitated, it is certain that the fnails, at leaft 
many of them, will repair the head. But what 
will enfue, if decoilation is towards the middle 
of September, or when the requifite heat does not 
continue with us more than a month, on account 
of the fupervening autumnal rains? I have in- 
ftituted many experiments for elucidating this cu- 
rious enquiry, and obtained the following refults : 
Tf the mutilated {nails were expofed to the heat 
of a ftove, equal or furpafling the neceffary de- 
gree, I was fure of reproduction before the end 
of winter. If kept in a fituation where, for fome 
days, they might be expofed to the cold of freez- 
ing, the greater part perifhed. When the cold 
was lefs, they retained the power of reproduc- 
_ tion, which re-appeared in fpring ; and the head 
and horns, having begun to grow at the com- 
mencement of winter, attained their full fize in 
the fubfequent fpring. If decollated in the be- 
ginning 
