1867.] SEXUAL SELECTION. 95 



dragon-fly painted with gorgeous colours, but I never had an 

 opportunity of fairly trying it. 



The reason of my being so much interested just at present 

 about sexual selection is, that I have almost resolved to 

 publish a little essay on the origin of Mankind, and I still 

 strongly think (though I failed to convince you, and this, to 

 me, is the heaviest blow possible) that sexual selection has 

 been the main agent in forming the races of man. 



By the way, there is another subject which I shall intro- 

 duce in my essay, namely, expression of countenance. Now, 

 do you happen to know by any odd chance a very good- 

 natured and acute observer in the Malay Archipelago, who 

 you think would make a few easy observations for me on the 

 expression of the Malays when excited by various emotions ? 

 For in this case I would send to such person a list of queries. 

 I thank you for your most interesting letter, and remain, 



Yours very sincerely, 



CH. DARWIN. 



C. Darwin to A. R. Wallace. 



Down, March [1867]. 



MY DEAR WALLACE, I thank you much for your two 

 notes. The case of Julia Pastrana * is a splendid addition to 

 my other cases of correlated teeth and hair, and I will add it 

 in correcting the press of my present volume. Pray let me 

 hear in the course of the summer if you get any evidence 

 about the gaudy caterpillars. I should much like to give 

 (or quote if published) this idea of yours, if in any way sup- 

 ported, as suggested by you. It will, however, be a long 

 time hence, for I can see that sexual selection is growing 

 into quite a large subject, which I shall introduce into my 

 essay on Man, supposing that I ever publish it. I had 



* A bearded woman having an irregular double set of teeth. See 

 ' Animals and Plants,' vol. ii. p. 328. 



