74 THE kntomologist's record. 



paragraph of this article), or has been caused by the external environ- 

 ment to which it responds, is quite another matter. We prefer to 

 consider the response to environment simply as the outward expression 

 of certain variable factors which must first arise, it seems to us (and to 

 Weismann also it would ajipear from other parts of his paper), within 

 the orf>;anism itself, and which are directed, as to what lines they shall 

 ultimately take, by the external conditions of life, as Weismann 

 intimates. 



To support his conclusion, Weismann considers in detail the 

 coloration of the exempt Heliconids, which have the same hues on the 

 upper and lower surfaces of the wings, and he suggests that it might 

 be said that "the coloration of the Heliconids runs through from the 

 upper to the under surface," and that, possibly, one might suppose 

 that the coloration was "the expression of a law." But, he argues, 

 " among numerous imitators of the Heliconids is the genus 

 l'rntn;ionii(.s, which has the coloration of the Heliconids on its upper 

 surface, but on its lower exhibits a magniticent leaf-design. During 

 flight it appears to be a Heliconid, and at rest a leaf. How is it 

 possible that two such totally dift'erent types of coloration should be 

 combined in a single species, if any sort of nuter rigorous necessity 

 existed, regulating the coloration of the two wing- surfaces ? " 



Surely Professor Weismann has shown us himself how the 

 evolution of two such dissimilar wing surfaces could arise from 

 internal forces. It is easy to show that during the process of 

 histogenesis in the pupa, the scales are built up, and Weismann him- 

 self has shown lis that the original determinants of the scales must be 

 equally subject to variation as those of the other organs, and equally 

 independent of each other ; and, also, that the determinants of the 

 scales on the lower surface of the wing are quite separate from, inde- 

 pendent of, and vary differently from, those on the upper sur- 

 face, and can, therefore, be developed on entirely different lines. 

 It is easy to understand, then, how two different colours (or patterns) 

 can be developed on the upper and lower surfaces of the wing- 

 respectively. 



We only state this to show that the Professor rather overplays his 

 part, and underestimates, to some extent, what internal forces 

 can do. Although, then, we disagree with this detail, we quite 

 agree with his conclusions, and believe that the direction which 

 these will take is determined by v;tility. It will be seen from 

 this that we are not among those who deny the efhcacy of 

 selection. Nor do we agree with those Avho think the directive 

 force which determines the character of these markings has its origin 

 within. What we do disagree with is the too generalised assumption 

 of the total inefficacy of internal forces, and the implied suggestion 

 that the external factor — utility— is sufficient to originate, and not 

 merely to direct. 



Returning to the Protoi/onius, the Professor continues : — " Now, 

 although we are unable to prove that the Protii(f(»ih(s species would 

 have perished unless they possessed this duplex coloration, yet it would 

 be nothing less than intellectual blindness to deny that the butterflies 

 in question are effectually protected, both at rest and during flight, and 

 that thrir colorations arc adajitirc." With this we quite agree ; so also 

 we do with the Professor's position that, " although we do not know 



