WORK ON ' MAN.' [1869, 



Down, March 3, 1869. 



DEAR SIR, I am very much obliged to you for your 

 kindness in sending me your spirited and interesting lecture; 

 if a layman had delivered the same address, he would have 

 done good service in spreading what, as I hope and believe, 

 is to a large extent the truth ; but a clergyman in delivering 

 such an address does, as it appears to me, much more good 

 by his power to shake ignorant prejudices, and by setting, if 

 I may be permitted to say so, an admirable example of lib- 

 erality. 



With sincere respect, I beg leave to remain, 



Dear Sir, yours faithfully and obliged, 



CHARLES DARWIN. 



[The references to the subject of expression in the follow- 

 ing letter are explained by the fact that my father's original 

 intention was to give his essay on this subject as a chapter in 

 the 'Descent of Man-/ which in its turn grew, as we have 

 seen, out of a proposed chapter in * Animals and Plants : '] 



C. Darwin to F, Miiller. 



Down, February 22 [1869?] 



. . . Although you have aided me to so great an extent in 

 many ways, I am going to beg for any information on two 

 other subjects. I am preparing a discussion on " Sexual Se- 

 lection," and I want much to know how low down in the ani- 

 mal scale sexual selection of a particular kind extends. Do 

 you know of any lowly organised animals, in which the sexes 

 are separated, and in which the male differs from the female 

 in arms of offence, like the horns and tusks of male mammals, 

 or in gaudy plumage and ornaments, as with birds and but- 

 terflies ? I do not refer to secondary sexual characters, by 

 which the male is able to discover the female, like the plumed 

 antennae of moths, or by which the male is enabled to seize 

 the female, like the curious pincers described by you in some 

 of the lower Crustaceans. But what I want to know is, how 



