( Ixx ) 



relations of this order, T fail to see why we should not con- 

 sider them now. As a matter of fact it does, however, seem to 

 me that Darwin did most distinctly admit this principle of phy- 

 siological correlation. There is, for example, the well-known 

 argument of Dr. Wells, quoted by Prof. Eay Lankester, cor- 

 relating the colour of the dark-skinned races of man with 

 immunity from the attack of malarial fevers. It will be found, 

 moreover, on reference to Darwin's writings, that he gives 

 many similar instances showing that, even within the limits 

 of the same species, certain constitutional differences, such 

 as immunity to natural poisons, are correlated with external 

 differences of colour, etc. There is, among others, the familiar 

 case of the black hogs of Virginia being less subject to suc- 

 cumb to the effect of eating the root of Laclinanthcs tinctoria 

 than those of other colours.* The same principle is adopted 

 and extended by Wallace, f who, in his last paper, sums up 

 the position by stating that " every truly sj)ecij/c character is 

 or has been useful, or, if not in itself useful, is strictly corre- 

 lated with such a character. "J There is here no limitation of 

 the term to structural correlations only, and I learnt from my 

 friend, Dr. Wallace, after the meeting, that he admitted cor- 

 relation, in the sense advocated by Prof. Lankester and myself 

 during the discussion. In justification of my own view I will 

 beg permission to quote from an obituary notice of Darwin 

 which was written in 1883, and which I now only make use 

 of because it occurs in a publication which may not be 

 generally accessible : — 



" It is most important to bear in mind that Darwin's prime 

 mover, natural selection, acts not only upon external 

 characters, but likewise upon internal organization ; minute 

 constitutional or physiologicial deviations at present utterly 

 beyond the ken of science, can be seized upon and perpetuated 



* " Origin of Species," 6tli ed., p. 9 ; " Variation of Animals," etc., Vol. 

 II., pp. 227-230 and 336 ; " Life and Letters," Vol. II., p. 300. See also 

 the concluding part of Chap. XXV. of the " Variation of Animals," etc. 



+ ''Darwinism," pp.140, 1/0. Also the section on the direct action 

 of the environment, pp. 418 — 420. See likewise Note 2, p. 42, of Weismaun's 

 latest essay on " Germinal Selection," 1S9C. 



X " Journ. Linn. Soc," Dec, 1896, Vol. XXV., p. 496. 



