156 MR. C. N. BARKER 



tlie nuineroiis cases of resemblance that occur in nature. 

 The disposition to vary among organisms in favour of 

 disphiy is to my mind a very real factor; and that the 

 male sex is the more susceptible to these influences gives 

 one good reason to assume that the incentive is primarily 

 sexual; that the male development is often followed on 

 by the female, which in some cases have caught up with 

 the male and in still rarer cases even passed him. 



It is for these reasons principally that I believe the 

 females of PapiUo dardanus-ceiica and of Hypolymnas 

 misippas are the more ancestral. The beauty of the but- 

 terfly's wing is largely governed by the desire for dis- 

 play, and the distinctiveness of certain types in certain 

 faunistic areas may be the result of climate acting on 

 susceptibilities responsive to the same stimuli, or, in 

 other words, that are following the same lines of develop- 

 ment. Variation must, in diverging from one type, con- 

 verge on some other (for colours and patterns are 

 limited), and in doing so resemblances must sometimes 

 be produced. If from any cause the colour, pattern, or 

 even contour, slionld ])rove beneficial to the insects^ na- 

 tural selection might maintain and even improve on the 

 resemblance, but that does not imply that it is simply 

 useful as a protective disguise (though it may be in some 

 cases), but rather that it is constitutionally correct, as 

 is the black skin of a negro to his environment. In the 

 course of ages more and more cases would occur of but 

 terflies developing on parallel or converging lines arriv- 

 ing at the same point, as we may assume Nos. 1 and 2 

 originally arrived at; i.e., at that point where the 

 physical conditions of their environment would directly 

 act ui)on their constitutions to bring about similar re- 

 sults and add yet further examples of the types sugges- 

 tive of the sub-region to which they belong. 



In spite of these restraining influences, be they 

 physical or due to natural selection, some butterflies im- 

 pelled by their constitutional forces, will continue to 

 vary, and this, more often than not, will be in the direc- 



