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. Gew3rbschule zu Elberfeld, 1877, 1878. 



