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wince Darwin and Wallai-i' lias hoon almost cxclusiv oly dovolcii — 1 

 moan llio origin of adaptations. Nod tliati lie does not nuMiliou t.licso, 

 ho assnnios in roga.rd to his nwitalions ■ a. soiootion workini;' in a con- 

 stant diroction,' and sooks to intorprot thoui in tornis of i(>, lint as tho 

 luntations occur i'roni pm'oly inti'rnal reasons — ^1 moan williont any 

 connexion witli tlio uocossity for a, now adaptation — and occnv t)nly in 

 a small porcontao-o ol' individuals, and in no dolinito diroction, thoy 

 cannot jiossihly suttico to explain in/n/ilttlioii, which soomsto dominate 

 the whole orj;'anic world. Hut this is precisely the point at which 

 many botanists coasi' to imdorstand the zoolo^'isIrS, ln'cause aimono- 

 plants there are I'ewor adaptations than anionji' animals ; or, in any 

 case, adaptations in plants are not so readily demonstrated ns iimonj;' 

 animals, which not inrro(inently soimu to ns to ho entirely Luilt up 

 oL" adaptations. 



In this hook, and in this chapter itself, 1 have discussed adapta- 

 tions and their origin so much already that 1 need only rol'i'r to l-lu>se 

 })aj;'os for convincing' e\idence that \ve cannot think of them as heing 

 brought about by the accunnilation and anginenta.tioii of individually 

 occurring saltatory ' nuitation.s.' Notr even if we assume that the 

 leaps of mutation can bi- inci'eased in tho course of gi^iu^rations ; in 

 short, e\Tn if we say that nuitations are all those variations which 

 breed true and lead to tho dcNclopnienl. of species, whil(> variations 

 are those which do not. This wo\dd only be playing with words, so 

 let ns say that the liuctuating variations nw ri^ally tliU'erent in th(>ir 

 nature, that is, in their causes, from nuitations. I)e \'ries lays great 

 8tre.ss on the fact that those two kinds of variations must bi^ sharply 

 distinguished from ono anotlu^r, and this may have be(>n useful or 

 necessary for the lirst investigation of tho facts before him, foi' we 

 nnist first analyse and then recondiino, but- that \jiria.tions and 

 nuitations are in reality did'erent in nature can assuredly not bo 

 assumed, since innumerable adaptations can only have arisen through 

 the augmentation of individiial variations, 'riusse must therefore b(^ 

 able to become 'pure breeding,' oscn altliongh they may not Iuivh^ 

 doim so in tho cases of artilicial seUx'timi which have hi(-herl,i) been 

 observed. Mow is it possibU' that chance mutations, in no particular 

 direction, occurring only rai-oly and in a small ]iercentM,ge of indi- 

 viduals, can explain tho origin of the leaf-marking of a KaUhnia or 

 an Anmi — the shifting of the original wing-nervnros to form li^af- 

 voins, and tho exact correla,tion o\ theH<i veins a,(^i'OHS the surfaces of 

 both pairs of wings'! And ovcmi if wo wei'c^ to admit that a nnilation 

 might have occuri'oil which (Niusod the vcuns of tho anterior and 

 posterior wings to moot exactly by chance, tliat would still not be 



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