610 Validity of the Doctrine of Mutation. 
those 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." 1 The doctrine of the direct influence 
of the environment on organisms, as entertained bv LA- 
o ^ 
MARCK, is that against which DARWIN directed his hy- 
pothesis of indeterminate variability as being more in 
harmony with the demands of pure science. This old 
doctrine is repeatedly met with in modern times, 2 and this 
shows at least, in my opinion, that the prevailing form 
of fhe theory of selection does not find favor in those 
quarters. 3 
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 either 
increase or diminish, strengthen or weaken the various 
characters. It cannot effect 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 
1 A. KUYPER, Evolutie, Amsterdam 1899, p. n. 
2 G. HENSLOW, Does Natural Selection Play any Part in the Ori- 
gin of Species, Nat. Sc., XT, 1897, p. 166. WARMING, Lehrbnch d. 
Oekologie, p. 382. VON WETTSTEIN, Ber. d. d. bot. Ges., 1900, Vol. 
XVIII, Generalversammlungsber. p. 184. STRASBURGER, Ceratophyl- 
hnn submersum, 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. 
3 R. v. WETTSTEIN, Haudbuch der systcmatischcn Botanik, 1901, 
p. 32. 
