Letters to Mr. Riley. 241 



to me, and I am struck with admiration at your 

 power of observation. The discussion on mimetic 

 insects seems to me particularly good and original. 

 Pray accept my cordial thanks for the instruction 

 and interest which I have received. 



What a loss to natural science our poor mutual 

 friend, Walsh, has been : it is a loss ever to be 

 deplored. 



Pray believe me, with much respect. 



Yours, very faithfully, 



Ch. Darwin. 



Down, 



September 28, 1881. Beckenham, Kent. 



My Dear Mr. Riley : I must write half-a-dozen 

 lines to say how much interested I have been by 

 your " Further Notes " on Pronuba, which you were 

 so kind as to send me. I had read the various 

 criticisms, and though I did not know what answer 

 would be made, yet I felt full of confidence in the 

 result, and now I see I was right. . . . 



If you make any further observation on Pronuba 

 it would, I think, be well worth while for you to ob- 

 serve whether the moth can or does occasionally 

 bring pollen from one plant to the stigma of a 

 distinct one ; for I have shown that the cross-fertili- 

 sation of the flowers on the same plant does very 

 little good, and, if I am not mistaken, you believe 

 that the Pronuba gathers pollen from the same 

 flower which she fertilises.* 



* This is a misapprehension. Pronuba is an effectual cross-fertiliser, 

 running from flower to flower, and often flying from raceme to raceme 

 with one and the same load of pollen. The omitted passages in this 

 letter refer to the work of a gentleman still living. 

 16 



