1872.] PUBLICATION OF THE EXPRESSION BOOK. 349 



your essay, I almost determined never to use again. There 

 are very few remarks in your book to which I demur, but 

 when you back up Asa Gray in saying that all instincts are 

 congenital habits, I must protest. 



Finally, will you permit me to ask you a question : have 

 you yourself, or some one who can be quite trusted, observed 

 (p. 322) that the butterflies on the Alps are tamer than those 

 on the lowlands ? Do they belong to the same species ? 

 Has this fact been observed with more than one species ? 

 Are they brightly coloured kinds ? I am especially curious 

 about their alighting on the brightly coloured parts of ladies' 

 dresses, more especially because I have been more than once 

 assured that butterflies like bright colours, for instance, in 

 India the scarlet leaves of Pointsettia. 



Once again allow me to thank you for having sent me 

 your work, and for the very unusual amount of pleasure 

 which I have received in reading it. 



With much respect, I remain, my dear Sir, 



Yours very sincerely, 



Charles Darwin. 



[The last revise of the ' Expression of the Emotions ' was 

 finished on August 22nd, 1872, and he wrote in his Diary : — 

 " Has taken me about twelve months." As usual he had no 

 belief in the possibility of the book being generally success- 

 ful. The following passage in a letter to Haeckel gives the 

 impression that he had felt the writing of this book as a some- 

 what severe strain : — 



" I have finished my little book on ' Expression,' and when 

 it is published in November I will of course send you a copy, 

 in case you would like to read it for amusement. I have re- 

 sumed some old botanical work, and perhaps I shall never 

 again attempt to discuss theoretical views. 



" I am growing old and weak, and no man can tell 

 when his intellectual powers begin to fail. Long life 

 and happiness to you for your own sake and for that of 

 science." 



