THE NAT URE OF METAMORPHOSIS. 
6 
crossing the oesophagus, c, is the nervous cord, and it passes down 
between the stomach and the skin. The 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 ligustri. (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 
