xiv] VARIABILITY OF SPECIES 



produce this form of intentional selection in Nature ? And who 

 has given the first impulse to the " accidental " production of a 

 new variation ? I do not deny that even at the present time some 

 form of adaptation can be artificially obtained. Thus horses better 

 adapted to draw than to run, and vice versa, have been produced ; 

 but even in these cases man has merely taken advantage of an 

 innate tendency in the horse, and has selected for interbreeding 

 those animals which, quite independent of any action on his part, 

 were born with one or with the other predisposition. 



The means employed by man to obtain varieties consist princi- 

 pally in endeavours to diminish the power and energy of conserva- 

 tive heredity, which obliges descendants to reproduce forms 

 identical with their progenitors. Such means are hybridizing and 

 interbreeding with different species or varieties ; and, above all, a 

 continued interbreeding of blood relations, descendants from the 

 same stock (the principal cause, perhaps, of duplication). Finally, 

 added to this is intentional artificial selection by man — a factor 

 which plays no part in Nature. 1 



The new forms thus obtained by cultivation in no case satisfy 

 a want newly developed in a plant or animal ; they reveal instead 

 merely a tendency towards independence so far as regards the 

 established laws of heredity ; and, indeed, many are probably merely 

 forms which have assumed some of the so-called ancestral or atavic 

 characters, i.e. those which formerly existed in progenitors of the 

 species and now reappear. 2 



I do not, however, entirely exclude the possibility that at the 

 present time some traces of true adaptation may yet be obtained, 

 But what I wish to show is that in all cases the actual power of 

 adaptation in organisms is at the present day well nigh non-existent 

 as compared with what they must have possessed in the past. It is 

 sufficient to give one case in point — that of the mangroves, trees 

 which live with their roots constantly submerged in salt water. 

 Would it be possible now to cause any of the innumerable trees 

 which grow in these tropical forests away from the sea to live and 

 flourish in salt water ? From time immemorial fruits of all sorts 

 of species have been carried by the rivers to the sea and deposited 

 at their mouths in favourable conditions for germination, yet, 



1 In many garden vegetables in which the hypertrophy of certain parts 

 is the chief feature, as in cabbages, carrots, radishes, etc., it may be suspected 

 that cultivation in a soil rich in nitrogenous compounds has produced the 

 development of micro-organisms, which through some special form of symbiosis 

 may be the cause of such hypertrophy. 



2 As an example I may say that I have obtained specimens of 

 Cyclamen per si cum with . perfectly straight peduncles and erect flowers, 

 with a corolla with open and horizontal petals, just as in a normal primula, 

 and as beyond doubt was the case in the progenitor of the cyclamen. 



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