SILK-WORMS. 239 
5th. Of the comparison between the grafted 
and wild mulberry-leaves. 
1 . Of the Small Silk-worm of Three Casts. 
I reared a certain quantity of these silk-worms 
separately, the eggs of which may be found in 
several parts of Lombardy, and close to my own 
habitation. 
These eggs of this species weigh one-eleventh 
less than the eggs of the common silk-worm ; 
39,168 of the latter forming an ounce, while 
42,620 of the smaller are required to make 
that weight. The silk- worms and cocoons of 
three casts are two-fifths smaller than those of 
the common sort. My experiments demonstrated 
that those worms consume, to form a pound of 
cocoons, nearly as great a quantity of leaves as 
that eaten by the larger species ; and although 
smaller when they have reached their highest 
growth, they devour more fragments and shoots 
of leaves than the common sort, so that in culti- 
vating the common sort, we perhaps save rather 
less of the shoots and leaves. 
The cocoons of the small silk-worm are com- 
posed of finer and more beautiful silk than the 
common cocoon (Chap. XIV.); but, however, they 
do not sell higher than the latter. It would appear 
