Phyktic I \iralielism in Metamorphic Species. 475 



We may therefore fairly assert that the structure 

 of larvae is on the whole remarkably uniform, in 

 consequence of the uniformity in the conditions of 

 life. Notwithstanding the great variety of exter- 

 nal aspects, the general structure of caterpillars 

 does not become changed it is only their outward 

 garb which varies, sometimes in one direction, and 

 sometimes in another, and which, starting from 

 inherited characters, becomes adapted to the 

 various special conditions of life in the best possible 

 manner. 



All this is quite different in the case of the 

 imagines, where we meet with very important 

 differences in the conditions of life. The butter- 

 flies, which live under the influence of direct sun- 

 light and a much higher temperature, and which 

 are on the wing for a much longer period during 

 the day, must evidently be differently equipped to 

 the moths in their motor organs (wings), degree 

 of hairiness, and in the development of their eyes 

 and other organs of sense. It is true that we are 

 .not at present in a condition to furnish special 

 proofs that the individual organs of butterflies are 

 exactly adapted to a diurnal life, but we may 

 safely draw this general conclusion from the cir- 

 cumstance that no butterfly is of nocturnal habits. 10 



to Hermann Miiller, and causes the anterior portion of the 

 caterpillar to resemble a spider. See note i, p. 290. R.M.] 



10 [Certain butterflies appear to be crepuscular, if not noc- 

 turnal in their habits. Thus in his " Notes on the Lepidoptera 



