SILK-WORMS. 
209 
cocoons which are to produce the male moth from 
those that contain the female ; but the least er- 
roneous, and best known, are the following :■ — 
The cocoon is smaller, sharper at one or both 
ends, ’and depressed in the middle, which generally 
produces the male ; the round full cocoon, with- 
out ring or depression in the middle, usually con- 
tains the female. 
In the following Chapter, we shall observe that 
the chrysalis and female cocoons are nearly twice 
as heavy as the male ; which must naturally pre- 
suppose that the female cocoon, all circumstances 
equal, must be larger than the male. 
Having composed tables of cocoons which I be- 
lieved to be all male, and others of female cocoons, 
I found that in both cases the greatest portion 
verified the signs I have described as likely to dis- 
tinguish them. 
A silk-worm, although female, will frequently 
form a small cocoon, sharp at the ends ; because, 
having had great vigour, it has moved, and turn- 
ed, and composed it with great ease and freedom ; 
whilst, on the contrary, when the insect is weak 
and languid, its motions are less powerful, which 
will often cause a male worm to form a large 
thick cocoon without any sharpness at the extre- 
mities. 
We must, therefore, conclude that the cocoons 
proceeding from well-managed laboratories, which 
are solid and fine-grained, are all likely to pro- 
