1890 OBJECTIONS TO THEOEY CONSIDEEED 207 



being a tremendous objection, it is also a tremendous 

 mystery. For, as it must admit of some explanation, 

 and as this explanation must almost certainly have 

 to do with the sexual system, it becomes not 

 improbable that when found the explanation may 

 square with p.s. That the difierence in question is 

 functional and not structural (or physiological as 

 distinguished from morphological) seems to be proved 

 by the fact that in some cases it obtains as between 

 the most closely allied genera, being, e.g., most 

 strongly pronounced of all between Geranium and 

 Pelargonium. Even quite apart from my own theory, 

 it seems to me that this is a subject of the highest 

 importance to investigate. 



As regards sexual selection I allow, of course, that 

 the ' law of battle ' is a form of natural selection. 

 But where the matter is merely a pleasing of aesthetic 

 taste, and the resulting structures therefore only 

 ornamental, I can see nothing ' advantageous ' in the 

 sense of life-preserving. On the contrary, in most 

 cases such structures entail considerable expenditure 

 of physiological energy in their production. On this 

 account Darwin says that nat. sel. must impose a 

 check on sexual selection running beyond a certain 

 point of injuriousness ('D. of M.,' p. 227). Now, 

 physiological selection is never thus injurious ; and 

 although it is a ' form of isolation,' the isolation is 

 neither so extreme nor of such long continuance as 

 the ones you compare it with. Moreover, the environ- 

 ment (therefore all other or external conditions of hfe) 

 remain the same, which is not the case under the 

 other forms of isolation. Provided that the physio- 



