STRUCTURE OF INSECTS. 



321 



tially annular, and that it resembles in this re- 

 spect the rings of which the thorax consists, and 

 to which it forms a natural sequel. 



150 



The head contains the brain, or principal en- 

 largement of the nervous system, and the organs 

 of sensation and of mastication. Its size, as com- 

 pared with the rest of the body, varies much in 



VOL. I. Y 



