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JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



words. . . . Thus I have been led to place somewhat more value on the 

 definite and direct action of external conditions ; to think the lapse of 

 time, as measured by years, not quite so great as most geologists have 

 thought ; and to infer that single variations are of even less importance 

 in comparison with individual differences, than I formerly thought."* 



If we look for a cause in Darwin's mind which led him henceforth 

 to regard evolution from an ecological point ol view, we shall find it 

 in the following letter to Lord Farrbr : " It is to me delightful to see 

 what appears a mere morphological character found to be of use. It 

 pleases me the more as Carl Nageli has lately been pitching into me 

 on this head. Hooker, with whom I discussed the subject, maintained 

 that uses would be found for lots more structures and cheered me by 

 throwing my own orchids into my teeth, "f 



To discover uses — i.e. adaptations and how they arise — is the very 

 essence of ecology. It is no exaggeration to say that every cell is of use 

 and every tissue indicates adaptation as the result of response to the 

 surrounding conditions of life. I will now select two sentences out of 

 many for comparison between the sixth and first editions of the ' * Origin 

 &c." " There can be little doubt that the tendency to vary in the same 

 manner [i.e. by resfoyise to the direct action of changed conditions] 

 has often been so strong that all the individuals of the same species have, 

 been similarly modified without the aid of any form of selection."! , 

 This does not occur in the first edition. 



In the following sentence the words ' ' natural selection ' ' are 

 omitted from the sixth, but are found in the first edition. " Within 

 a confined area . . . natural selection will always tend to preserve all 

 the individuals varying in the right direction. "§ In the sixth edition 

 we read : ' ' All the individuals varying in the right direction . . . will 

 tend to be preserved. "|| r 



In replying to Mr. St. G. Mivart's criticism, Darwin observes: 

 " He often assumes that I attribute nothing to variation, independently 

 of natural selection) whereas, in my " Variation under Domestica- 

 tion "H I have collected a greater number of well-established cases 

 than can be found in any other work known to me."'-'* 



Nevertheless Darwin observes : " It appears that I formerly under- 

 rated the frequency and value of [the direct action of external con- 

 ditions] as leading to permanent modifications of structure, inde- 

 pendently of natural selection. When I wrote the * Origin ' [1859] 

 and for some years afterwards I could find little good evidence of the 

 direct action of the environment. Now there is a large body of 

 evidence. "it Perhaps it was due to Dr. Weismann's influence that 

 Darwinians lost sight of "direct action" — i.e. on the soma — and 



* Life, ct-c, iii. pp. 110, 111. 



+ G. Darivin and the Origin of Species, by E. B. Poulton, pp. 20, 21. 



X Origin, tbc, sixth edition, p. 72. § Op. cit., first edition, p. 102. 



II Op. cit., sixth edition, p. 80. 



H Variation of Animals and Plants under Domestication, ii. p. 273. 

 ** Origin, d-c, sixth edition, p. 421. 

 tt Life, cCr., iii. p. 159. 



