82 



SCIENCE. 



[N. S. VOL. XXIV. No. 603. 



driving." And as the display of mental den- 

 sity increased with time, he wrote to Hooker/ 

 "I am inclined to give np the attempt as 

 hopeless. Those who do not understand, it 

 seems, can not be made to understand." 



The scientific world has largely learned the 

 first lesson — that of open-mindedness — ^but 

 two recent articles in Science' suggest that we 

 have not learned the other. 



It is not my intention here to pose as an 

 advocate of de Vries, nor as a self-appointed 

 interpreter of the mutation theory. The 

 writings of its author are too clear to need 

 any additional elucidation. But it is impor- 

 tant, before we discuss the theory, to be sure 

 that we thoroughly understand it. A perusal 

 of the articles just cited makes it difl&cult to 

 believe that their authors have given the 

 writings of de Vries a very thoughtful reading. 



Calling attention at the outset to the im- 

 portance of understanding the terms used by 

 de Vries, the author of the first article says: 

 " What we systematists have been in the habit 

 of calling spontaneous variations or 'sports' 

 he calls '' mutations.' " This is doubtless one 

 of the commonest, and at the same time most 

 fatal, errors to a correct understanding of mu- 

 tation. ' Mutations ' and ' sports ' are by no 

 means synonymous terms, as used by de Vries, 

 and, after he has devoted several pages to 

 carefully defining these terms, and to showing 

 that, while mutations are a kind of ' sport,' 

 not all sports are mutations, it seems difficult 

 to understand how one who had gotten his 

 notions of the theory at first hand could per- 

 sist in the former loose usage of the terms. 

 The distinction drawn by de Vries is clear. 

 For example, he says," " in order to avoid 

 confusion as far as possible, with the least 

 change in existing terminology, I shall use 

 the term ' ever-sporting varieties ' for such 

 forms as are regularly propagated by seed, 

 and of pure and not hybrid origin, but which 



^L. c, Vol. II., p. 109. 



^ Merriam, C. Hart, ' Is Mutation a Factor in 

 the Evolution of the Higher Vertebrates ? ' Sci- 

 ence, February 16, 1906. Ortmann, A. E., 'The 

 Fallacy of the Mutation Theory,' Science, May 

 11, 1906. 



* ' Species and Varieties,' p. 310. 



sport in nearly every generation." Citing the 

 striped variety of the larkspur as the first il- 

 lustration, he continues : " Such deviations 

 are usually called sports. But they occur 

 yearly and regularly,'" and for this and other 

 reasons they are not mutations." Of these 

 later. 



Again our critic tells us that, " What we 

 call individual variations he calls ' fluctv/p- 

 tions.' " And yet on page 77 of ' Species and 

 Varieties ' we read, " From a broad point of 

 view, fluctuating variability falls under two 

 heads. They obey quite the same laws and 

 are, therefore, easily confused, but with re- 

 spect to questions of heredity they should be 

 carefully separated. They are designated by 

 the terms individual and partial fluctuation." 

 Individual variation and fluctuation, then, are 

 not synonyms, for some fluctuations are ' par- 

 tial ' and not ' individual,' and this difference 

 is explained and illustrated in the following 

 twenty -three pages.^ 



On page 242' we are told that de Vries " ap- 

 pears to have been carried away with enthu- 

 siasm over his discovery and jumps to the 

 conclusion that species in general originate 

 by mutation — and in no other way!"^ 



' Species and Varieties ' does not profess^" 

 to treat at length the problem of hybridiza- 

 tion, yet lecture IX. deals with the subject, 

 and on page 266 the author refers to the fact 

 that " Kerner von Marilaun pointed out the 

 fact long ago that many so-called species, of 

 rare occurrence, may be considered to have 

 originated by a cross," and nearly a score of 

 well-authenticated illustrative examples fol- 

 low, with the sanction of de Vries as to the 

 hybrid origin of the species. 



" And has any reason been brought forward 

 to justify — much less necessitate — a change in 

 this belief ? " " {i. e., that differences in char- 



"L. c, p. 11. 



" Mutations are distinguished from other kinds 

 of sports, among other ways, by being ' of very 

 rare occurrence.' L. c, p. 191. 



' See also pp. 190 and 191, and lecture XXVIII. 



^ Merriam, I. c. 



" Italics mine. 



"Cf. p. 250. 



"Merriam, p. 247. 



