Februaky 1, 1907] 



SCIENCE 



187 



sidering the fact that, in Europe, (Enothera 

 lamarchiana is surely an escaped garden-form, 

 and that it actually has been there under the 

 care of florists for a long time, the possibility 

 that it might be found in the wild state in 

 America does not affect in the least degree the 

 very tempting assumption that its strange 

 behavior is due to cultivation with all its in- 

 herent and accessory incidents, exactly as is 

 the case in other garden-forms. 



MacDougal regards it as a specimen of ' lit- 

 erary license ' and ' inaccuracy ' (p. 213), when 

 I say that de Vries entirely failed to take 

 notice of the principle that the discovery of 

 intermediate forms serves to show that two 

 supposed true breeding forms do not possess 

 the rank of species as understood by the 

 taxonomist, and that he also failed to show 

 that his so-called elementary species are not 

 connected by intermediate forms. I do not 

 see where the ' license ' and ' inaccuracy ' come 

 in, for it is a fact that de Vries nowhere re- 

 ported that he went over the whole area of 

 any of the species used or referred to by him, 

 and tried to ascertain whether there are any- 

 where such forms. Indeed, he reports that on 

 rare occasions he found something which 

 might be taken for connecting forms, but he 

 never searched carefully and conscientiously 

 for them. On the other hand, I know posi- 

 tively from m.y own experience that such 

 forms do exist at least in some of the ele- 

 mentary species discussed by de Vries : I 

 found them myself in nature in the group of 

 Viola tricolor and lutea, and saw them in the 

 case of Draha verna in de Bary's laboratory.' 



As regards my ' estimate of the futility of 

 experimental methods ' and my ' mistrust ' of 

 them, MacDougal (p. 213) has not understood 

 my standpoint. I have never said anything 

 that might be construed as if I 'mistrusted' 

 experiments or believed them to be ' futile,' 

 on the contrary, I fully agreed that experi- 

 ments ought to be made, but warned against 

 too great complexity and improper interpreta- 

 tion.' I chiefly called attention to the com- 

 plexity of conditions offered in culttires in the 



' See also : Stone, W., in Science, May 4, 1906, 

 p. 701, with reference to Viola. 



' Science, June 22, 1906, p. 952. 



botanical garden, which is met by MacDougal 

 (p. 213) by the statement that it is not the 

 case, that ' domesticated races ' have resulted 

 from the 'effects of tillage.' But, disregard- 

 ing the fact that ' tillage ' is only one of the 

 many factors contributing to the peculiar fea- 

 tures of environment in the garden, I never 

 said that the effect of tillage (or any other 

 environmental factor) is the production of 

 ' domesticated races.' I attribute to the en- 

 vironment the power to influence ' variation,' 

 but in order to obtain ' domesticated races,' 

 that is to say, forms which breed true, I always 

 insisted that pedigree-culture is necessary. In 

 nature the analogous process, selection and 

 segregation, leads to the formation of species. 



II. It is possibly well to present here again 

 my objections to de Vries's mutation theory, 

 and, to further the correct understanding of 

 my views, I shall try to represent the matter 

 in a somewhat different form, emphasizing 

 chiefly what are the undoubted facts, and 

 what are their interpretations on the part of 

 de Vries and on my part. 



My first and fundamental contentions are: 



1. De Vries's conception of ' elementary spe- 

 cies ' is inadequate. There are, indeed, forms 

 in nature which have a tendency to breed true, 

 but which are not isolated from other forms, 

 but these forms should not be called species. 

 They have been called, for instance, by Dar- 

 win,' ' varieties,' and are distinguished by this 

 quality from ' variations.' On the other hand, 

 there are in nature true ' species,' character- 

 ized by the fact that the tendency to breed 

 true is fully developed, and that there are no 

 connecting links any more with allied forms: 

 they are separated from the latter. This char- 

 acter furnishes a good definition for the term 

 ' species,' which ought to be the taxonomic 

 species. This, however, does not mean that 

 in every ease it should be easy or even pos- 

 sible to distinguish sharply between a variety 

 and a species, since there are actual cases of 

 transition in nature. Yet at the present state 

 of our knowledge, the insufficiency of the 

 latter alone prevents in many cases a final 

 decision." 



"Darwin, 'Origin of Species,' p. 33. 



" See Pr. Amer. Philos. Soc, 35, 1896, p. 191. 



