730 



SCIENCE. 



[N. S. Vol. XXIV. No. 623. 



and thus a uniform response of individuals to 

 environment is rendered impossible." 



A. E. Ortmann. 

 Carnegie Museum, Pittsburg, Pa., 

 September 22, 1906. 



DISCONTINUOUS VARIATION. 



Dr. Jordan's kindly comment upon my 

 Wood's Hole lecture would place me at a 

 great disadvantage if I were inclined to be 

 controversial (Science, 24: 399, 1906). This, 

 however, is farthest from my purpose, and in 

 fact is unnecessary since I find myself in 

 agreement with him on most of the points 

 brought up. 



Too much emphasis can not be put upon 

 some of the statements reiterated or advanced 

 by Dr. Jordan, and he has certainly performed 

 a very useful service by approving the prin- 

 ciple that the students of a group, or of any 

 phase of life are more likely to acquire better 

 first-hand knowledge of it, and to render 

 truer interpretations of the facts obtained 

 than other writers. As vividly obvious as 

 this may be, it has been necessary to be un- 

 pleasantly insistent upon it upon various occa- 

 sions during the last few years, and to re- 

 assert that botanists are better fitted by oppor- 

 tunities and training for the comprehension 

 of the nature and behavior of plants than any 

 other class of naturalists. The dictum of 

 Darwin so aptly quoted has never been more 

 strictly applicable than at the present time, 

 and an intimate and accurate acquaintance 

 with a large number of species constitutes a 

 very important share of the competency for 

 profitable study of evolutionary problems. 

 Whether or not the investigator publishes his 

 descriptions is purely incidental. 



On the other hand, it is not to be granted 

 (and happily it is not) that a keen critical 



^* See Brooks, ' Heredity and Variation : Logical 

 and Biological,' in Pr. Amer. Philos. Soc, 45, 

 1906, p. 7'5. ' The species is * * * in that recip- 

 rocal interaction between the living being and the 

 natural world, of which it is a part.' This paper 

 of Brooks is quite interesting and important. 

 Although largely written in terms rather unusual 

 in the discussion of evolutionary matters, it brings 

 out ideas, which, if I correctly understand them, 

 are essentially in agreement with my own views. 



sense in nomenclature, or a zeal for the ac- 

 quisition, making or conservation of type speci- 

 mens forms a suitable equipment for the intel- 

 ligent consideration of genetics, although 

 when coupled with detailed studies in life- 

 histories, cultures and field observations, the 

 activities in question become of very great 

 value in this connection. 



During the last few years I have had occa- 

 sion to discuss the species-idea with several of 

 the more active systematic botanists, and find 

 that the theoretical conceptions of species 

 formulated by them vary widely, although 

 overlapping in many essential points in all 

 instances. Now these differences of opinion 

 by no means lead me to deprecate species- 

 making, or to distrust the value of the species 

 erected by these workers, although known to 

 apply differing standards. This knowledge 

 and this confidence are shared by the general 

 botanical public. The difficulty in delimiting 

 in so many words the difference between con- 

 tinuous and discontinuous variation is of a 

 similar character, and was recognized by my- 

 self in the earliest review of the work of de 

 Vries on the subject published in an American 

 journal in the following words : " From the 

 reviews and discussions which have already 

 been made of de Vries' papers it is to be seen 

 that the greatest misunderstanding which may 

 likely arise in the consideration of his results 

 will be that founded on the error of confusing 

 fluctuating variability and mutability." In 

 this as well as in the consideration of species 

 it is found that our difficulties disappear when 

 we deal with concrete examples, especially if 

 embraced in a pedigreed culture. To be able 

 to examine a number of organisms in the field 

 and determine which are continuous and 

 which are discontinuous variants is not pos- 

 sible, for Numerous reasons, although many 

 botanists have assumed to do so. 



What the actual origin of (Enothera La- 

 marckiana may have been can not be said : we 

 can vouch for the actual origin of but few 

 species. If records are to be trusted, however, 

 it was in cultivation in the Paris Garden a 

 century ago. My own breeding experiments 

 have included a number of crosses involving 

 various combinations of species from eastern 



