216 



SCIENCE. 



[N. S. Vol. XXIV. No. 607. 



tained after a number of generations, as is 

 seen in de Vries's experiments. 



This is so evident, that it is simply aston- 

 ishing that Gager is not capable of seeing it, 

 even after attention has been called to it, and 

 that he does not see that this is an important 

 part of my objections, namely, that it is selec- 

 tion and segregation that make mutants hreed 

 true. Indeed, he asks :* " "Where, from cover to 

 cover, of ' Species and Varieties,' is any other 

 claim made ? " Please look at the title : ' Spe- 

 cies and Varieties, their Origin by Mutation ' ; 

 is this identical with ' Species and Varieties, 

 their Origin by Selection and Segregation'? 

 In my opinion, the first phrase means that by 

 the process of mutation species (elementary 

 species, which breed true) are made; the 

 second, that selection and separation make 

 them breed true. The first means that the 

 quality of breeding true was created by the 

 mutation process, before de Vries made the 

 experiments, and (as de Vries says in the text) 

 that the latter were undertaken only in order 

 to testj to ascertain the existence of this qual- 

 ity; while the second means that the quality 

 of true breeding was created, not by the proc- 

 ess of mutation, but by the subsequent proc- 

 esses of selection and segregation. If Gager 

 can not see the difference, I am sorry for him ; 

 or should it again be a case of mental density 

 on my part? 



If we remove this fundamental fallacy out 

 of de Vries's theory, that it is not the process 

 of mutation, but that of selection and segrega- 

 tion, which makes species breed true, nothing 

 remains but the view that mutation is a pe- 

 culiar kind of variation, which alone may start 

 the species-making process, or which alone is 

 apt to finally produce true breeding forms. 

 A part of my article is written with reference 

 to this possible claim, although I know very 

 well that de Vries did not make it separately," 

 but always in connection with the first claim, 

 that it is the process of mutation which 

 produces true-breeding, elementary species. 



»!/. c, p. 87. 



" That I did not intend to represent this as de 

 Vries's view, but only as a possible modification 

 of it, is clearly seen in Science, June 22, 1906, 

 p. 950, foot-note 9. 



Gager" quotes my sentence,^ but omits the 

 introductory and important words : ' aside 

 from the above claim.' This, of course, af- 

 fords him a chance to show that I have mis- 

 understood de Vries. But if we exclude the 

 only test for the elementary species, that they 

 should be true-breeding forms, as unsatisfac- 

 tory, no other difference remains between 

 fluctuating variation and mutation, but the 

 degree or amount of deviation from the orig- 

 inal type, the one being represented by ' small 

 steps,' the other by * sudden leaps ' ; and I must 

 repeat that I am unable to draw a line between 

 them. If Gager" again points to de Vries's 

 definition of mutation (that it causes true 

 breeding), I hardly can call this a fair criti- 

 cism or a fair understanding of my views, 

 after I have expressly excluded this criterion. 



In this last instance, and in a few others, 

 Gager directly distorts what I am saying. I 

 have said" that ' in the beginning of the ex- 

 periments, they (the mutations or mutants) 

 were throwing off additional mutants.' Gager" 

 omits the words ' in the beginning of the ex- 

 periments,' and quotes the sentence as if it 

 was clearly implied that I meant to say that 

 ' all the mutants were throwing off additional 

 mutants.' In fact, I did not mean to say 

 ' all,' for this would not correspond to the 

 facts ; and the words ' in the beginning of the 

 experiments ' are essential for the proper un- 

 derstanding of the whole paragraph, and of 

 my contention that the mutants did not breed 

 true, namely, in the beginning : they bred true 

 later on, in conseqiisnce of the experiment, 

 which was the point I wanted to bring out. 



Further, when I say" that ' the breeding of 

 domestic races has always been regarded as a 

 process analogous to the one in nature by 

 which new species are produced,' ' always ' 

 does not mean: by everybody and at all times. 

 If it is hinted at by Gager" that I possibly 

 might have intended to include Linnaeus or 



"L. c, p. 87. 

 ^ L. c, p. 747. 

 " L. c, p. 88. 

 "L. c, p. 747. 

 "Z/. c, p. 86. 

 ^^ L. c, p. 747. 

 "L. c, p. 87. 



