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SCIENCE. 



[N. S. Vol. XXIII. No. 581. 



which he kept under observation for a 

 period of years, suddenly developed ab- 

 normal new characters or 'qualities' that 

 were inherited and gave rise to permanent 

 new species, which continued to exist side 

 by side Avith the parent species. This proc- 

 ess he calls 'the origin of species by mu- 

 tation.' While admitting the extreme 

 rarity of occurrences of this kind, he ap- 

 pears to have been carried away with 

 enthiisiasm over his discovery and jumps 

 to the conclusion that species in general 

 originate by mutation— and in no other 

 way! 



After stating that species 'are not in 

 the main distinguished from their allies by 

 quantities nor by degrees; the very qual- 

 ities may differ,' he goes on to say that if 

 the differences in quality can not be ex- 

 plained 'by the slow and gradual accumu- 

 lation of individual variation,' and if the 

 sudden variations called sports or muta- 

 tions, 'can be shown to occur in nature as 

 well as they are known to occur in the 

 cultivated condition, then in truth Darwin- 

 ism can afford to lose the individual varia- 

 tions as a basis.' Continuing the argu- 

 ment, he declares : ' ' Then there will be two 

 vast dominions of variability, sharply 

 limited and sharply contrasted with one 

 another. One of them [that of individual 

 variation] will be raled by Quetelet's law 

 of probability and by the unavoidable and 

 continuous occurrence of reversions. It 

 will reign supreme in the sciences of an- 

 thropology and sociology. Outside of 

 these, the other [that of sports or muta- 

 tions] will become a new domain of in- 

 vestigation, and will ask to be designated 

 by a new name" — the origin of species by 

 mutation. There would seem to be no 

 doubt as to de Vries's meaning. The ques- 

 tion is, are his assumptions .justified by the 

 facts in nature? It will be observed that 

 he deems the perpetuation of individital 

 variations jeopardized 'by the unavoidable 



and continuous occurrence of reversions.' 

 Let me ask in all seriousness if sport varia- 

 tions are less likely to disappear by rever- 

 sion than are individual variations? 



Let us now examine the 'if and ands' of 

 de Vries 's argument. The first of these is : 

 If the differences in quality [characters] 

 'can not be explained by the slow and 

 gradual accumulation of individual varia- 

 tions * * *.' May one venture to ask. 

 Why can they not be so explained? Is it 

 not true that up to the time of the an- 

 nouncement of his new theory a little more 

 than a year ago it was the practically 

 unanimous belief of zoologists and botanists 

 the world over that the differences in quality 

 that go to make species do originate in pre- 

 cisely this way ? And has any reason been 

 brought forward to justify— much less ne- 

 cessitate—a change in this belief? Are we, 

 because of the discovery of a case in which a 

 species appears to have arisen in a slightly 

 different way— for after all the difference 

 is only one of degree— to lose faith in the 

 stability of knowledge and rush panic 

 stricken into the sea of unbelief, unmindful 

 of the cumulative observations and conclu- 

 sions of zoologists and botanists? 



De Vries's second and third ifs are: "If 

 such strains [produced artificially among 

 cultivated plants] can be proved to offer 

 a better analogy to real systematic species, 

 and if the sudden changes can be shown 

 to occur in nature as well as they are 

 known to occur in the cultivated condition, 

 then in truth Darwinism can afford to lose 

 the individual variations as a basis. ' ' The 

 logic of this is hard to see, for is it con- 

 ceivable that 'strains,' or varieties pro- 

 duced artificially among cultivated plants, 

 'can be proved to offer a better analogy to 

 real systematic species' than species pro- 

 duced in the normal way by the perpetua- 

 tion of individual variations? 'And if the 

 sudden changes [sports or mutations] can 

 be shown to occur in nature'— and I admit 



