SILK-WORMS. 
13 
r . It is evident that by this contraction, by the 
emission of the silk, and continual evaporation, 
(Chap. VIII. § 7), the skin shrinks and wrinkles, 
the rings approximate, and the insect becomes 
gradually smaller. 
The formation of the chrysalis then begins, 
which is accomplished when the silk is entirely 
drawn out, and when the wrinkled slough of the 
animal is cast in the cocoon. 
It appears from this, that nature in the various 
modifications of the caterpillar, only tends to the 
simplification of the animal. 
Thus the caterpillar is in the first instance com- 
posed of animal, silky, and excremental particles: 
this forms the state of the growing caterpillar; 
in the next instance, it is composed of animal and 
silky particles; it is then the mature caterpillar; 
and, lastly, it is reduced to the animal particles 
alone, and is termed, in this state, the chiysalis ; 
the cocoons, or shells, which caterpillars form, 
vary much in shape, as we may observe on several 
occasions. 
Some species of caterpillars, filling small spaces 
begin their cocoon with several ends of silken 
thread, placing themselves in the centre, without 
however hiding themselves. Others unite and 
fasten together with the silky substance, one or 
more leaves ; thus sheltered to enable themselves to 
draw their silk in safety previous to their transi- 
