632 MUTATION THEORY OF PBOFESSOR DE VRIES. 



destined to make a strong impression of that kind upon biologists 

 because of its eminently scientific presentation, and because it promul- 

 gates a theory of the origin of species by mutation that is in material* 

 disagreement with the Darwinian theor}^ of their origin by natural 

 selection. The work is to consist of two volumes, the second of which 

 will probably not be fully published before the end of 1902. The 

 mutation theory therein enunciated, howev^er, has been foreshadowed 

 in previous lesser publications bj' the same author^ it is so fully stated 

 in the alread}' published parts of the present work, and is so remark- 

 able in its character, that it is thought proper to present a brief state- 

 ment of its leading features at this time. 



The subject-matter of this work is arranged under two principal 

 heads for the two volumes, respectively, namely, "The Origin of 

 Species by Mutation," and "Elementary Hybridit3^" Necessarily, 

 only the first volume can now be considered, but that contains the 

 onl}" part which I should care to discuss at the present time, even if 

 the other volume were now published. In fact, I shall discuss only 

 that portion of Volume I which contains the formal exposition of the 

 mutation theory. The author presents his subject stronglj^ and une- 

 quivocally, but with evident candor and sincerity of purpose and after 

 long and patient investigation. As I wish to give the author's views 

 of his mutation theory as far as possible in the English equivalent of 

 the language used by him, the following quotations are selected alter- 

 nately and translated from the author's preface, introduction, and text, 

 respectively: 



"The doctrine of the origin of species has hitherto been a conven- 

 tional science. It is generally believed that this important occurrence 

 isi withdrawn from actual observation, or at least from experimental 

 treatment. This conviction is founded upon the prevailing conception 

 concerning specific characters and upon the opinion that species of 

 plants and animals are always produced from one another by extremely 

 slow degrees. It is thought that these metamorphoses are so slow 

 that a human life is not long enough to witness the production of a 

 new form. The purpose of the present work is to show the opposite 

 view — that species originate by sudden starts, and that each one of 

 these saltatory occurrences is, as good observations show, a true 

 physiological process; that all such suddenly produced forms are sepa- 

 rated from one another by at least as sharp and numerous characters 

 as are most of the so-called minor species, and as are many of the 

 nearly related forms of the best systematists. It is thus made pos- 

 sible to fearn by means of actual observation, cultivation, and experi- 

 ment the laws which govern the production of new species. These 

 laws are evidently as applicable to animals as to plants. As a botan- 

 ist, I have confined myself to the latter, but in the confident hope that 

 my results will later be also employed in the study of animals. 



"The whole subject of variability falls under two heads — variability 

 in the narrow sense and mrtation. The first is variously designated 

 as common, individual, and fiuctuating, or gradual variability. 

 Mutation forms a special division of the methods of variation. It does 



