182 



The Natuealtst. 



instances of animals exhibiting a sense of pleasure in certain sounds 

 and colours. It would be superfluous to go into details liere, as 

 doubtless you all know how completely Darwin has proved his case ; 

 but it is essential to the due appreciation of the whole of the following 

 argument that this should be remembered. 



I cannot open the discussion better than in Darwin's own words. 

 They are as follows: — "Every one must have admired the extreme 

 beauty of many butterflies and of some moths ; and it may be asked, 

 are their colours and diversified patterns the result of the direct action 

 of the physical conditions to which these insects have been exposed, 

 without any benefit being thus derived 1 Or have successive variations 

 been accumulated and determined as a protection, or for some unknov/n 

 purpose, or that one sex mav be attractive to the other 1 And again, 

 what is the meaning of the colours being widely difi'erent in the males 

 and females of certain species, and alike in the two sexes of other 

 species, of the same genus f 



Darwin next mentions, on the authority of Mr. Bates, that in the 

 South American genus Epicalia there are twelve species the sexes of 

 which haunt the same stations, of which nine species have males which 

 rank amongst the most brilliant of all butterflies, and are so different 

 from the comparatively plain females that they were formerly ranked 

 in different genera. The females of these nine species resemble one 

 another, and also resemble those of allied genera found in various parts 

 of the world. He argaes from this that the nine species are descended 

 from an ancestral form coloured in nearly the same manner, and that 

 the males alone have been changed ; by sexual selection. In the tenth 

 species the male resembles the female, thus strengthening this view. 

 In the tv/o remaining species both males and females are beautifully 

 coloured, though the female in a somewhat less degree. Thus, out of 

 twelve species nine have females which resemble one another and the 

 females of allied genera much more closely than they resemble the 

 males of their own species, in one male and female are about alike, 

 and in the remaining two species both male and female are highly 

 coloured. These facts clearly point to the conclusion that it is the 

 males that have become altered by selection (in this case sexual), and 

 that in the two exceptional species the females have become modified 

 through inheritance from the males. 



But this is no isolated instance. Darwin gives a number of others, 

 which I need not here repeat, and concludes his examples by 

 remarking that even amongst our English butterflies we have a good 

 case in point. In Lycana agestis,'^ he says^ " both sexes have a 



