SILK-WORMS. 
113 
no longer shining and black, as it appears in the 
two first ages, but it is lengthened and more 
prominent. 
The head and body is much enlarged since 
the casting of the skin, even before they have 
eaten at all ; proving that they were straight- 
ened in the skin they have cast, and being now 
unconfined, the air alone has expanded their 
bulk. 
This growth, which is considerable, is more 
visible in this age than in the preceding. 
When this age is completed, the body of the 
silk-worm is more wrinkled, particularly about 
the head ; they are of a yellowish white, or rather 
fawm colour ; and to the naked eye they have no 
appearance of hairiness. 
The membranaceous feet, and particularly those 
at the hinder extremities, have acquired much 
strength, and an adhesive quality which enables 
the silk-worm strongly to retain any thing it 
touches. In this third age we first hear, when 
the worms are fed, a little hissing noise, similar 
to that of green wood burning. 
This noise does not proceed from the action of 
the jaws, but from the motion of the feet, which 
they are continually moving ; this noise is such, 
that in a large laboratory it sounds like a soft 
shower of rain ; by degrees, when the worms fas- 
ten to their food, the noise ceases. 
