THE STUDY OF HEREDITY 341 



generations, a consideration of the nature of the evidence is 

 necessary. Prof. Thomson gives a full account of the evidence 

 on both sides which occupies eighty-five pages of his book. He 

 is able to arrive only at the following conclusion, however, 

 which he obviously considers to be of the utmost importance, as 

 he prints it in italics : 



" If there is little or no scientific warrant for our being other than 

 extremely sceptical at present as to the inheritance of acquired 

 characters — or better, the transmission of modifications — this scepticism 

 lends greater importance than ever on the one hand to a good 

 ' nature, 1 to secure which is the business of careful mating ; and, 

 on the other hand, to a good ' nurture 1 to secure which for our 

 children is one of our most obvious and binding duties ; the hope- 

 fulness of the task resting especially upon the fact that, unlike the beasts 

 that perish, man has a lasting external heritage, capable of endless 

 modifications for the better, a heritage of ideas and ideals, embodied 

 in prose and verse, in statue and painting, in cathedral and university, 

 in tradition and convention, and above all in society itself." 



This does not seem to help very much. Prof. Hartog's 

 evidence is all one-sided. Beyond what I have already said as 

 to the improbability of the transmission of acquirements, we find 

 that, in fact, a very favourable environment when applied to all 

 the individuals of a race tends to result in the disappearance of 

 characters. Characters are preserved only when necessary or 

 beneficial to the individual. But necessary and beneficial 

 characters, or rather the potentiality of producing them, must 

 generally be of such a nature as to enable their possessors to 

 resist or overcome unfavourable factors in the environment. But 

 unfavourable factors in the environment must always be injurious 

 to the individual, and if the inheritance of the response to the en- 

 vironment be accepted it involves the belief in the evolution of a 

 potentiality, which must be present in every individual, of selecting 

 which kind of acquirement is to be inherited and which is not — 

 just as big a result in itself as all the rest of evolution without 

 it. Without something of this kind an unfavourable environ- 

 ment must necessarily cause a race to grow weaker, while a 

 very favourable environment would cause it to grow stronger. 

 We know that this is not what happens. On the other hand, 

 that the capacities for development along certain lines should 

 be produced by the selection of favourable variations occurring 

 in individuals seems easy to understand. 



