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JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



variations, as he calls them, natural selection — in Darwin's application of 

 the term — has no place in nature. 



When Darwin wrote his book (1859) he was, to a limited extent, 

 acquainted with this fact ; but he thought it was very exceptional, and 

 certainly not the rule. He gives us a hint, even so early as in the Intro- 

 duction to the first edition of the " Origin, &c." He thus wrote : " Natural 

 selection is the main, but not the exclusive, means of modification." This 

 is explained on the eleventh page, wherein he adds : " Some slight amount 

 of change may, I think, be attributed to the direct action of the conditions 

 of life ; " i.e. by the plant responding by making adaptive structures. 



When we turn to his "Animals and Plants under Domestication" 

 (1868), we find that he is much more positive about it. His words 

 are : " The direct action of changed conditions of life leads to definite or 

 [assumed] indefinite results. By the term 1 Definite Action,' I mean an 

 action of such a nature that when many individuals of the same variety 

 are exposed during several generations to any change in their physical 

 conditions of life, all, or nearly all, the individuals are modified in the 

 same manner. A new sub-variety would then be produced without the 

 aid of selection." * 



The reader will now perceive that " Indefinite " and " Definite " 

 results must be mutually exclusive. A batch of seedlings cannot all vary 

 alike (i.e. definitely) and at the same time have the majority with injurious 

 variations (i.e. indefinitely). In 1859, however, Darwin seemed to have 

 thought that natural selection was somehow aided by " definite action " 

 of the environment ; but he evidently came to the conclusion that such a 

 combination was quite inadmissible in 1868. 



In another passage in his " Animals and Plants unde.r Domestication " 

 he speaks yet more strongly, for he observes : " The direct and definite 

 action of changed conditions, in contradistinction to the accumulation of 

 indefinite variations, seems to me to be so important that I will give a large 

 additional body of miscellaneous facts" ; and he adds about thirty more 

 to the one only which previously he had regarded as " the most remark- 

 able case known to me, namely, that in Germany several varieties of maize 

 brought from the hotter parts of America were transformed in the course 

 of only two or three generations." t 



By the year 1876 we find that Darwin had become even more thoroughly 

 convinced of the importance of "Definite Action," by which he means, 

 " Direct action of new or changed conditions of life producing definite 

 results, or adaptive variations "—for he wrote to Professor Moritz Wagner 

 as follows : t — " The greatest mistake I made was, I now think, I did not 

 attach sufficient weight to the direct influence of food, climate, &c, quite 

 independently of natural selection. When I wrote my book, and for some 

 years later, I could not find a good proof of the direct action of the environ- 

 ment on the species. Such proofs are now plentiful." 



After this, one is not surprised to read in the sixth edition of the 

 "Origin of Species," published two years afterwards (1878): "There can 

 be little doubt that the tendency to vary in the same manner has often 



* Animal* and Plants under Domestication, vol. ii. p. 271 ; see also Origin, dr., 

 pp. «;. 7*2, B0| Ac. (6th ed.). 



+ .1;/. and J'i. under Dam. ii. pp. 277-381. + Life, vol. iii. p. 169. 



