EVOLUTION 1017 



of the natural selection factor — the pruning hook of the growing 

 and varying arhor vitce. But while we find him approving of the 

 neat criticism: "Natural selection may explain the survival of the 

 fittest, but it does not explain their arrival", we should also notice 

 his broadminded attitude to the central theory of Darwinism, as in 

 the sentence : "Variations may arise slowly, from simple fluctuations, 

 or suddenly, by mutations ; in both cases natural selection will take 

 hold of them, will multiply them if they are beneficial, and in the 

 course of time accumulate them, so as to produce that great 

 diversity of organic life, which we so highly admire." Yet many too 

 readily accept psychologically warped asseverations to the effect 

 that natural selection is not of much importance in evolution. In 

 saying "psychologically warped" we allude to the familiar vice of 

 experts who, having discerned some one factor with intense vivid- 

 ness, let us say Mendelian inheritance, are thereby impelled to 

 depreciate every other factor. But because one happens to have 

 had a revelation of Brahma the creator (giving origin to mutations), 

 one does not feel it necessary to deny the power of Kali the 

 destroyer (natural selection, in fact). 



Therefore, while we do not wish to appeal to authority, we would 

 quote De Vries again, for he has done so much in the way of 

 illuminating investigation. What does he say in the Darwin Cen- 

 tenary essays? "The origin of new species, which is in part the effect 

 of mutability, is, however, due mainly to natural selection. 

 Mutability provides the new characters and new elementary species. 

 Natural selection, on the other hand, decides what is to live and what 

 is to die." Here there is nothing but clearheadedness in regard to 

 the difference between originative and directive (or sifting) factors. 



It is useful now and again to point out that a sieve does not 

 make what it sifts, and that the pruning shears do not exactly cause 

 the tree to grow ; and its reiteration was provoked by too exclusive 

 insistence on "the All-Sufhciency of Natural Selection". It was 

 quite useful for Samuel Butler to gibe in his inimitable fashion at 

 the extremest Darwinism (beyond Darwin): "It does not explain 

 to me how I came here, that my uncles and aunts went away." 

 But such a witty jest has much more justification than Driesch's: 

 "Darwinism . . . explained how, by throwing stones, one could build 

 a house of typical style." 



It is a pity that people who sway public opinion on difficult 

 questions do not read a little more before they make their 

 deliverances. Thus in very few recent evolutionist discussions have 

 we seen anything that would lead us to suppose that the disputant 

 had taken account of such an important investigation as Baur's 

 study of snapdragons (Antirrhinum), in which it is shown, after 

 many years of research, that the garden races are constantly 

 exhibiting small mutations, transmissible in their entirety in 



