xm 



his work, ' On Expression of the Emotions in Man and Animals,' 

 then under preparation. 



Almost casually, in one of his letters to Darwin (14th March, 1871), 

 thanking him for a copy of ' The Descent of Man,' Donders thus 

 summarises in our language his own views of 1847 : " I always took 

 a great interest in the question of the origin of organised beings. 

 Even in 1847 I wrote and published an essay (oratio inauguralis) on 

 the subject ' Harmony of Animal Life, a Manifestation of Laws,' con- 

 taining, from the physiological point de vue, a farther development of 

 the doctrine which had been indicated by Lamarck, although the 

 communications on this subject of Lamarck were as unknown to me 

 as almost to every one, in that period. Fully excluding final causes 

 from scientifical research and theory, I tried to show how the infinite 

 harmonical relations, on the one hand, between animals and sur- 

 rounding nature, on the other hand, between the different parts and 

 organs of every organism, are to be deduced from the laws of adapta- 

 tion by habitude and by exercise, and from the laws of transmission. 

 I applied the same on the psychical actions. I admitted the gradual 

 evolution of the highest orders of plants and animals from more 

 simple forms of spontaneous origin, and the origin of different specie? 

 from the same source. I indicated the changes which are obtained 

 by artificial selection, found the cause of continual progress in the 

 circumstance that every not well adapted form necessarily is con- 

 demned to perish, but still was not aware of the influence of natural 

 selection, your great and immortal discovery, the mighty factor, 

 which alone allowed to give a full and special demonstration of the 

 theory of descent. As I began to write, I had not the intention to 

 mention to you my little book, but, telling about my special interest 

 in the subject, I rather involuntarily inclined to explain it. And 

 now, although it is Written in Dutch, I could not resist my wish to 

 send you a copy, in the hope that you will benevolently accept it. 

 . . ." Darwin replies (18th March, 1871), "... I have been 

 interested in what you tell me about your views, published in 1848, 

 and I wish I could read your essay. It is clear to me that you were 

 as near as possible in preceding me on the subject of Natural Selec- 

 tion." And afterwards (June 19th, 1871), "... When reading 

 over your several letters, the thought has often crossed my mind how 

 incomparably better an essay on expression you could have written 

 than that which I shall be able to produce. . . ." ; (April 8th, 

 1872) " . . . I feel, every day. that to write on Expression, a man 

 ought to have ten times as much physiological knowledge as I possess. 

 . . ." ; and (December 21st, 1872) "... My book on Expres- 

 sion, in writing which I was so deeply indebted to your kindness "- 



' Life and Letters of Charles Darwin,' by Francis Darwin, vol. 3, and C. DarwitL 

 ' On Expression, &c.,' 1872, p. 160. 



