456 FERTILISATION OF FLOWERS. [1878 



fairly astonished at the number of species of insects, the visits 

 of which to different flowers you have recorded. You must 

 have worked in the most indefatigable manner. About half 

 a year ago the editor of ' Nature ' suggested that it would be 

 a grand undertaking if a number of naturalists were to do 

 .what you have already done on so large a scale with respect 

 to the visits of insects. I have been particularly glad to read 

 your historical sketch, for I had never before seen all the 

 references put together. I have sometimes feared that I was 

 in error when I said that C. K. Sprengel did not fully per- 

 ceive that cross-fertilisation was the final end of the structure 

 of flowers ; but now this fear is relieved, and it is a great 

 satisfaction to me to believe that I have aided in making his 

 excellent book more generally known. Nothing has surprised 

 me more than to see in your historical sketch how much I 

 myself have done on the subject, as it never before occurred 

 to me to think of all my papers as a whole. But I do not 

 doubt that your generous appreciation of the labours of others 

 has led you to over-estimate what I have done. With very 

 sincere thanks and respect, believe me, 



Yours faithfully, 

 CHARLES DARWIN. 



P.S. I have mentioned your book to almost every one 

 who, as far as I know, cares for the subject in England ; and 

 I have ordered a copy to be sent to our Royal Society. 



[The next letter, to Dr. Behrens, refers to the same sub- 

 ject as the last :] 



C. Darwin to W. Behrens. 



Down, August 29 [1878], 



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

 sent me your 'Geschichte der Bestaubungs-Theorie,'* and 

 which has interested me much. It has put some things in a 



* Progr. der K. Gewerbschule zu Elberfeld, 1877, 1878. 



