ANIMAL REPRODUCTIONS. 373 
‘It muft be obferved, that a certain degree of 
heat is required for reproduction, and ‘not lefs 
than 61°. Reproduction is finally nothing but a 
new generation, with this fingle inconfiderable 
diftinGtion, that in ordinary generation aa orga 
nifed whole originates and unfolds, while in re- 
produétion only a part of that whole is developed. 
The fame conditions requifite for the origin of the 
whole are required for the origin of a part, and 
among thefe conditions is heat. In man, qua- 
drupeds, and moft other warm blooded animals, 
the foetus originates at any feafon, becaufe it is 
matured in the body of the mother, where there 
is always a certain degree of heat. Birds may 
hatch their eggs in winter by means of their 
heat. It is otherwife with cold animals : they 
do not and cannot propagate except in warm 
weather ; for during the reft of the year they are 
in fuch a fituation from cold, that, to judge by 
external appearances, we fhould rather fay they 
were dead than alive. Thus it is with moft in- 
fects, worms and reptiles, among which laft, {naibs 
ought to be numbered. They neither copulate 
nor generate except in fummer. Shut up in 
their calcareous dwellings, and the mouth cover- 
ed with the operculum formed of that vifcous ! 
gluten exuding from the body, they remain mo- 
tionlefs, and in a lethargic ftate, under the earth 
all winter. Not only are they incapable of gene- 
rating 
