i860 l88a] DESCENT OF MAN 47 



To G. Rollcston. Letter 415 



Bassett, Southampton, Sept. 2nd [1875]. 

 I am much obliged to you for having sent me your 

 Address, which has interested me greatly. I quite subscribe 

 to what you say about Mr. Bagehot's striking remark, and 

 wish I had not quoted it. I can perceive no sort of reflection 

 or blame on anything which I have written, and I know well 

 that I deserve many a good slap on the face. The decrease 

 of savage populations interests me much, and I should like 

 you some time to look at a discussion on this subject which 

 I have introduced in the second edition of the Descent of Man, 

 and which you can find (for I have no copy here) in the list 

 of additions. The facts have convinced me that lessened 

 fertility and the poor constitution of the children is one chief 

 cause of such decrease ; and that the case is strictly parallel 

 to the sterility of many wild animals when made captive, 

 the civilisation of savages and the captivity of wild animals 

 leading to the same result. 



To Ernst Krause. Letter 416 



Down, June 30th, 1877. 



I have been much interested by your able argument x against 

 the belief that the sense of colour has been recently acquired 

 by man. The following observation bears on this subject. 



I attended carefully to the mental development of my 

 young children, and with two, or as I believe three of them, 

 soon after they had come to the age when they knew the 

 names of all common objects, I was startled by observing that 

 they seemed quite incapable of affixing the right names to the 

 colours in coloured engravings, although I tried repeatedly to 

 teach them. 1 distinctly remember declaring that they were 

 colour-blind, but this afterwards proved a groundless fear. 



On communicating this fact to another person he told 

 me that he had observed a nearly similar case. Therefore 

 the difficulty which young children experience either in dis- 

 tinguishing, or more probably in naming colours, seems to 



1 See /Cosmos, June 1877, p. 264, a review of Dr. Hugo Magnus' 

 Die Geschichtliche Entwickelung des Farbensinnes, 1S77. The first part 

 is chiefly an account of the author's views ; Dr. Krause's argument 

 begins at p. 269. The interest felt by Mr. Darwin is recorded by the 

 numerous pencil-marks on the margin of his copy. 



