The Making of Species 



from accepting his theory of mutations in toto. 

 We are, however, convinced that he, like Bate- 

 son, is on the right track. There can be no 

 doubt that a great many new forms have 

 originated suddenly, by jumps, and not by 

 imperceptibly slow degrees. Before giving a 

 list of the names of some of the races, both 

 plant and animal, which appear to have come 

 into existence suddenly, it will be of advantage 

 to consider for a little some of the more 

 important conceptions of De Vries. 



That eminent botanist, as we have already 

 seen, insists on the distinction between fluc- 

 tuating variations and mutations. The former 

 correspond, for all practical purposes, to the 

 continuous variations of Bateson, and the latter 

 seem to be equivalent to his discontinuous 

 variations. 



According to De Vries, all plants display 

 fluctuating variation, but only a small percentage 

 exhibit the phenomenon of mutation. The 

 most daring of his conceptions is, that the history 

 of every species is made up of alternating 

 periods of inactivity, when only fluctuating 

 variations occur, and of activity when " swarms 

 of species " are produced by mutation, and of 

 these only a few at the most survive ; natural 

 selection, which De Vries likens to a sieve, 

 determining which shall live and which shall 

 perish. 



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