HOLOMETABOLOUS INSECTS 



57 



approximates closely to the formula for a constant differential 

 growth-ratio (Table IV, Fig. 35). Again, however, there can be 

 no growth-ratio in the literal sense in which we have found 



Fig. 34. — Heterogony of the ' tail ' in the male of the swallow-tail butterfly, 



Papilio dardanus (the heterogony is stated by Champy not to occur in species 



in which the ' tail ' occurs in both sexes). 



it apply, e.g., to the partition of growth-potential between 

 the large chela of Uca and the rest of the body. There cannot 

 be, for the simple reason that in holometabolous insects the 

 organ, as regards its imaginal characters, is not formed until 



