90 THE AMERICAN NATURALIST [Vol. XLIII 



disputed any of De Vries's propositions except the last. 

 All would have had to stand or fall with that. He 

 recognized the fact that new species had sometimes ap- 

 peared suddenly without intermediate steps and that the 

 new forms had sprung laterally from the main stem. I 

 think he also substantially admitted that such new species 

 attained their full constancy at once. As to the fourth 

 affirmation of De Vries, with reference to elementary 

 species and retrograde varieties, Darwin had no knowl- 

 edge, for the distinction is original with De Vries. Dar- 

 win believed, as a general proposition, that 1 1 species are 

 only strongly marked and permanent varieties, and that 

 each species first existed as a variety, ' ,53 but, of course, 

 in admitted cases of mutation this can not be true ; and 

 if Darwin had been obliged to concede De Vries 's seventh 

 proposition, the fourth might well have been allowed to 

 go with it. The same is doubtless the case concerning 

 De Vries's fifth law, which sets forth in effect that similar 

 mutants are thrown off by many individuals of the same 

 species at about the same time. As we have already 

 seen, Mr. Darwin was convinced that if, for example, he 

 were to admit the origin by mutation of a species of flying 

 animal, for the reasons urged by Mr. Mivart, he would 

 be compelled to assume "that many individuals varied 

 simultaneously." I, therefore, do not see that he would 

 have been interested, from a theoretical point of view, in 

 disputing either of the two last-named declarations of De 

 Vries except in connection with his seventh and last law, 

 to which I shall presently refer. The sixth law of De 

 Vries, which affirms that mutations take place in nearly 

 all directions, is practically the equivalent of Darwin's 

 first law that all organisms vary continually and in every 

 part of their structure, provided it is agreed that muta- 

 tions are only quantitatively different from Darwin's 

 "individual variations," which was Darwin's own view. 

 In so far as Darwin admitted the occurrence of mutation 

 at all, he must have agreed that it could proceed in any 



""Origin of Species," 6th ed., 1882, p. 412. 



