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 there- 

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

 that, to make the difference between survival and elimina- 

 tion, the favourableness of the variation must reach a 

 certain amount, varying with the keenness of the struggle. 

 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 is 

 admitted by Prof. Weismann as a real one. " The 

 Lamarckians were right," he says, "when they main- 

 tained that the factor for which hitherto the name of 

 natural selection had been exclusively reserved, viz. 

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

 insufficient for the explanation of the phenomena." * And 

 again,t "something is still wanting to the selection of 

 Darwin and Wallace, which it is obligatory on us to 

 discover, if we possibly can." 



The additional factor which Dr. Weismann suggests is 

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

 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." Monut, Jan., 1896, p. 290. 

 t Op. dt., p. 264. 



