i8g6. LYELL AND LAMARCKISM 331 



skin is tanned brown by the sun. The former changes are adaptive 

 and beneficial ; the latter would not usually be called an adaptation, 

 though it may on investigation be found to be beneficial. It is an 

 instance of the ' other effects ' of the environment, and is obviously 

 not haphazard, but definite and constant. Brooks asks if there is 

 any evidence that the effects of the environment are inherently 

 beneficial, and the reply is shown by the above considerations to be 

 that, whether beneficial or not, the same conditions acting constantly 

 produce a definite effect. We are here considering, not congenital 

 variations — those which, like a supernumerary digit, arise in a 

 single individual without obvious relation to the conditions of life — 

 but exclusively the effect of external conditions on the individual 

 during life. 



Brooks thinks that natural selection, if it act at all, must result 

 in adaptation, and that therefore it is a much more plausible theory 

 than the Lamarckian. But this is begging the question : natural 

 selection means the survival of adaptive variations, and the question 

 is the origin and cause of such variations. Lamarckians do not 

 admit that such variations have been proved to occur without the 

 direct action of the conditions of life; therefore to assert that natural 

 selection must produce adaptation is to assume the very proposition 

 in dispute. Even if it were proved that the variations were indepen- 

 dent of the conditions of life, the mere selection of them in itself 

 would not be an explanation ; we should still want to know the true 



causes of them. 



J. T. Cunningham. 



