3io Habit and Instinct. 



Now, what is natural selection, at any rate, as under- 

 stood by Darwin ? It is a process whereby, in the struggle 

 for existence, individuals possessed of favourable and 

 adaptive variations survive and hand on their good seed, 

 while individuals possessed of unfavourable variations suc- 

 cumb, and are sooner or later eliminated, standing the 

 fore a less chance of begetting offspring. But it is cle 

 that, to make the difference between survival and elimin 

 tion, the favourableness of the variation must reach a 

 certain amount, varying with the keenness of the struggl 

 And one of the difficulties which critics of natural selection 

 have felt is that the little more or the little less of varia- 

 tion must often be too small in amount to be of selection- 

 value, so as to determine survival. This difficulty 

 admitted by Prof. Weismann as a real one. 

 Lamarckians were right," he says, "when they ma 

 tained that the factor for which hitherto the name 

 natural selection had been exclusively reserved, vi 

 personal selection [i.e. the selection of individuals], was 

 insufficient for the explanation of the phenomena." 

 again,f "something is still wanting to the selection 

 Darwin and Wallace, which it is obligatory on us 

 discover, if we possibly can." 



The additional factor which Dr. Weismann suggests 

 what he terms " germinal selection." This, briefly state 

 is as follows : There is a competition for nutriment among 

 those parts of the germ named determinants, from which 

 the several organs or groups of organs are developed. 

 In this competition the stronger determinants get the 

 best of it, and are further developed at the expense of 

 the weaker determinants, which are starved and tend to 

 dwindle and eventually disappear. The suggestion is 



* "Germinal Selection." Monist, Jan., 1896, p. 290. 

 t Op. cit., p. 264. 



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