332 
THE ART OF REARING 
always soiled inside and outside ; and even when 
perfectly di*y, they retain a sort of stain. They 
never are so clear as those cocoons which have 
been cut when the chrysalis was alive, and conse- 
quently they are heavier. 
That nothing may be concealed from those that 
wish to rear silk-worms, I will here state the pro- 
portionate difference which may be observed in 
the pierced cocoons from which moths have 
issued : — 
ozs. 
1000 ounces of these cocoons only weigh about . 170 
The remains or envelopes of the worm which is be- 
come chrysalis . . . . . 
The remains of the chrysalis which the moth leaves 
on issuing from the cocoon . . . 7| 
. ,i 183 
The 1000 ounces of cocoons chosen for eggs 
have, then, yielded rather more than the sixth 
part of the weight of the empty cocoon ; they 
weigh 170 ounces, when the 1000 ounces of co- 
coons with the empty chrysalis only yielded 
153 ounces of pure cocoon. 
Before I conclude my observations on the healthy 
chrysalis, I shall quote a fact that may appear sur- 
prising. — It requires 12,860 cocoons to form 
1000 ounces. It has been seen that the remains 
or envelopes of this same quantity of silk-worms, 
weigh about 4h ounces. Let us suppose that the 
