CHAPTEK II. 



THE CATERPILLAB. 



THE caterpillar is a worm-like animal, plainly 

 separated into two principal parts, a head and 

 body ; and the latter into a number of rings, 

 which may be clustered by certain features into 

 two tracts, a thoracic and an abdominal. The head 

 itself is in reality made up of a number of rings, 

 consolidated in such a way as to render their sep- 

 arate determination one of the most difficult tasks 

 of the morphologist, just as our own head is com- 

 posed of a number of primal vertebrae. The hard 

 parts of an insect are upon the outside, while ours 

 are within ; and just as our backbone is made up 

 of a series of vertebrae ranged in a row, a single 

 vertebra being, as it were, the unit of structure, 

 so the outer coating of an insect is broken up into 

 a series of rings, laid end to end, each the unit of 

 its structure. The number of elemental rings 

 forming the head of a caterpillar is still a matter 

 of dispute, and would be a subject perhaps too 

 abstruse in the present state of science to discuss 

 here. It may only be said that no one ring will 

 be found to bear on its under surface more than 

 a single set of jointed appendages, and that the 



