(dlO I'alidity of tiw Doctrine of Mutation. 



tliose the least adapted to the immediate external condi- 

 tions. Selection is the elimination of the inferior, whilst 

 the choice of the superior individuals should be called 

 ''election, " and this leads to the stock-races {elite races) 

 as in the selection of beets and cereals (Vol. I, pp. 99- 

 118); or, as an admirable critic, A. Kuyper^ says, "se- 

 lection aims at the maintenance of species ; election is the 

 choice of persons."^ The doctrine of the direct influence 

 of the environment on organisms, as entertained b\- La- 

 marck, is that against which Darwin directed his hy- 

 i:)Othesis of indeterminate variability as being more in 

 harmony with the demands of pure science. This old 

 doctrine is repeatedly met with in modern times,- and this 

 shows at least, in my opinion, that the prevailing form 

 of the theory of selection does not find favor in those 

 quarters.'" 



Thus the sieve of natural selection perpetually elim- 

 inates numerous individuals of inferior value; but how 

 the differences between the individuals arise is another 

 question. Linear variability provides differences only in 

 two directions, by means of which selection can eitlier 

 increase or diminish, strengthen or weaken the various 

 characters. It cannot eft'ect more, unless material of an- 

 other kind is provided by variation. The hypothesis of 

 mutation meets this demand ; for it necessarily assumes 

 a variability in almost all directions, as I have shown 



L\. KuYPER, Evohitic, Amsterdam 1899, p. 11. 



^G. Henslow, Docs Natural Selection Play any Part in the Ori- 

 gin of Species, Nat. Sc, XT. 1897, p. t66. Warming, Lehrhucli d. 

 Oekologie, p. 382. Von Wettstein, Ber. d. d. hot. Ges., 1900, Vol. 

 XVIIT. GeneralversammUinofsber. p. 184. Strasburger, Ccratophyl- 

 Uim suhmersiim, Jahrb. f. wiss. Bot., Vol. XXXVII. p. 518. where a 

 list of references to papers, dealing with the direct effect of the en- 

 vironment, will be found. 



^ R. V. Wettstein, Handhiicli der systcmatischen Botanik. 1901, 

 P- 32. 



