THE NATURE OF METAMORPHOSIS. 



6l 



crossing the oesophagus, c, is the nervous cord, and it passes down 

 between the stomach and the skin. Tlie shape of the digestive 

 apparatus is noticed to be very different in the three conditions, 

 and the shortening of the body is very distinctly shown : a is the 

 dorsal vessel, or the heart, and i part of the reproductive apparatus. 



SECTIONS OF THE LARVA, PUPA, AND MOTH OF Sphinx Ugnsiri. (After Newport. ) 



(In all the figures the numbers from i to 13, upon the dorsal or upper surfaces, 

 note the segments. 



" The body of the insect is now divided into three distinct 

 regions — head, thorax, and abdomen. The first step towards this 

 division is the contraction which takes place in all the longitudinal 

 and diagonal muscles of the body soon after the larva has acquired 

 its full size, by means of which each segment of the insect forms a 

 slight intussusception, the anterior margin of one segment being 



