August 17, 1906.] 



SCIENCE. 



215 



essence of my views, and further, that other 

 publications of mine on this and kindred sub- 

 jects, which are absolutely necessary for the 

 proper understanding of my views, are un- 

 known to him. 



The chief purpose of my article was to ob- 

 ject to de Vries's conception of mutation and 

 elementary species. If I object to these terms, 

 of course, I do not accept them, and since I 

 have given reasons for believing that they are 

 wrong, the only appropriate rejoinder to this 

 would be to show that my reasons are no good. 

 Instead of this, Gager is satisfied with the 

 vague and superficial statement that it is 

 impossible to satisfactorily define the concept 

 of species, neglecting entirely what I have 

 written on this topic previously,^ and, further, 

 he spills a good deal of ink in reiterating 

 de Vries's contentions. 



Gager says :* " When a careful worker says 

 that he obtained a given form that breeds 

 absolutely true, and which, for reasons fully 

 explained, he calls an ' elementary species,' by 

 m,eans of a certain definite and clearly ex- 

 plained hind of variation which he defines and 

 names ' mutation' let us not refer to him as 

 ' claiming to ' have done so, or to the mutant 

 as ' seeming to ' breed true." 



Here we have a concise statement of de 

 Yries's claim, namely, that he obtained a form 

 that breeds true by means of mutation. I 

 have said^ that de Yries claims ' that mutants 

 are species.' But if de Yries calls a form 

 that breeds true an elementary species, he 

 obtained species by means of mutation; and 

 if the product of the process of mutation is a 

 mutant, of course, a mutant is obtained by 

 means of mutation, and, consequently, mu- 

 tants are {elementary) species. Thus it is 

 evident that my expression of de Yries's claim 

 is absolutely correct and identical in its mean- 

 ing with that given by Gager, and his allega- 

 tion that I have misunderstood de Vries is 

 entirely unwarranted. It rather seems that 

 Gager himself has not fully understood what 

 de Yries says, at any rate, that he was not 



^ Pr. Amer. Philos. Sac, 35, 1896. 

 *L. c, p. 89. 

 ^ L. c, p. 746. 



aware of the true meaning and import of d« 

 Yries's theory. This is due, in part, to the 

 fact that de Yries himself was not conscious 

 of the logical consequences of his views, he 

 belonging to the class of writers who are ob- 

 livious of the most fundamental principles of 

 evolution.' 



However, as I have endeavored to show, 

 I do not accept the view that mutants are 

 species, or that de Vries obtained a form that 

 breeds true by means of mutation. In op- 

 position to this I say, that he obtained such a 

 form by means of selection and segregation 

 out of a certain hind of variation {mutation). 

 Indeed, Gager endorses also the latter view'^ 

 by an emphatical ' Exactly ! ' and asks : ' why 

 the dissenting critique ? ' 



This plainly shows that, for Gager, these 

 two phrases are identical, namely, that de 

 Yries obtained species by means of mutations, 

 and that he obtained them by means of selec- 

 tion and segregation out of mutations. Pos- 

 sibly my mental density comes in here; but 

 I can not help it; I must regard these two 

 phrases as having a different meaning, and 

 this is the reason for my ' dissenting critique ' ; 

 de Yries never said anything that might be 

 interpreted in the sense of the second sentence. 



That de Yries's view is wrong I have dem- 

 onstrated by pointing out that the mutants 

 actually did not breed true before he started 

 his experiments, and very likely they would 

 not have bred true if he had not taken them 

 under his care. They began to breed true, not 

 because they were mutants, formed by the 

 process of mutation, but because he introduced 

 two factors, which were absent previously, 

 namely, selection and segregation. ' Pedigree- 

 culture is, the method required,' as Gager' 

 quite correctly insists, but apparently without 

 knowing of what it consists. The essential 

 factors in pedigree-culture are selection and 

 segregation, and pure strains are only ob- 



« See Ortmann, Science, Jime 22, 1906, p. 947 flf. 



'L. c, p. 87, in the form: 'If de Yries had 

 claimed that species might he made out of muta- 

 tions' (Ortmann, p. 747), namely, as is said in 

 the same paragraph, but carefully omitted by 

 Gager, hy means of selection and segregation. 



«L. c, p. 86. 



