632 MUTATION THEORY OF PKOFESSOR 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 theoiy of the origin of species by mutation that is in material 

 disagreement with the Darwinian theory 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, however, has been foreshadowed 

 in previous lesser publications by the same author, it is so fully stated 

 in the already 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 Hybridity." Necessarily, 

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

 only 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 strongly 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 

 i Si withdrawn from actual observation, or at least from experimental 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 team 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 mutation. The first is variously designated 

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

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



