1897] ORIGIN OF SPECIES AMONG PLANTS 171 



dependent upon geological catastrophes for producing variations in 

 plants and animals ? Indeed, this would seem to be Darwin's view 

 in his discussion on geologic time, in which he says : — " It is 

 probable, as Sir W. Thomson insists, that the world at a very early 

 period was subjected to more rapid and violent changes in its 

 physical conditions than those now occurring; and such changes 

 would have tended to induce changes at a corresponding rate in the 

 organisms which then existed." 1 



But when we find that one species will change into another 

 recognised species under our very eyes, if its environment be altered, 

 why need one appeal to millions of years for aid ? Dr Wallace, 

 e.g., notes how " Arabis anchoretica has tissue-papery leaves due 

 to its growth in hollows in the rock. Seeds of this plant when 

 cultivated at Kew produced the common species A. alpina. The 

 same thing occurs with many plants as every cultivator knows." 



Darwin and Dr Wallace agree in requiring " rapid adaptation," 

 but Darwin admits " that natural selection generally acts with 

 extreme slowness." 3 



Now, if nature has to wait for catastrophes before some 

 "chanced conditions of life" come to her organisms, is not this 

 something like trying to bring the mountain to Mahomet, instead 

 of letting Mahomet walk to the mountain ? Which is easier to 

 do, to let plants and animals migrate to a place with a different 

 climate and abundance or deficiency of altered food, rather than 

 imagine the latter to come to them ? 



Migration is so obvious a process that Darwin cannot help 

 alluding to it, as when he says : — " Among animals which unite for 

 each birth and are highly locomotive, doubtful forms ranked by one 

 zoologist as a species and by another as a variety, can rarely be 

 found within the same country, but are common in separated areas." 4 

 They have not, therefore, arisen at one common spot. 



A new climate and abundance of food are often supplied by 

 domestication and cultivation, and the anticipated results follow, 

 viz., variation ad libitum, the consequences also being often heredi- 

 tary as they are in nature. 



Acquired Characters are Hereditary in Plants. — Dr Wal- 

 lace writes : — " Climate and Food undoubtedly produce modifications 

 in the individual, but it has not yet been proved that the modifications 

 are hereditary. If this could be proved the whole discussion on 

 the heredity of acquired characters would be settled in the 

 affirmative." 5 But surely cultivation proves it every day ? Our 

 garden vegetables are all derived from wild plants, and they come 

 true by seed. 



1 "Origin, etc.," p. 286. ■ Natural Science, vol. v. p. 182. 3 "Origin, etc.," p. 84. 

 4 "Origin, etc.," p. 37. 5 " Darwinism," p. 489. 



