42 PHYLOGENY 



world at large has moved forward in sympathetic accord to the close 

 of a truly "Wonderful Century." 



Few, however, would now claim that Darwin's solution was 

 entirely conclusive and complete. From the nature of the case, 

 Darwin could not exhaust the problem, and no one has made this 

 clearer than Darwin himself, who examined his own theory with 

 such critical acumen and breadth of knowledge that he anticipated 

 nearly every important objection that has since been urged by others. 

 A problem that is at once the focal point of each and every one of the 

 biological sciences is not to be exhausted by one man, however long 

 and successful his work. The problem has grown larger rather than 

 smaller with every new contribution to its solution. The expansion 

 of its horizon, however, has not, and, as I believe, is not likely to dis- 

 close the "death-bed of Darwinism." We have heard the predictions, 

 but have witnessed no fulfillment. 



Among the rival theories of natural selection two are especially 

 noteworthy. One of these is now generally known as orthogenesis. 1 

 Theodore Eimer was one of the early champions of this theory, 

 basing his arguments primarily upon his researches on the variation 

 of the wall-lizard (187-1-81). Eimer boldly announced his later 

 works on The Origin of Species (1888), and the Orthogenesis of the 

 Butterflies (1897), as furnishing complete proof of definitely directed 

 variation, as the result of the inheritance of acquired characters, and 

 as showing the utter "impotence of natural selection." Eimer's intem- 

 perate ferocity toward the views of Darwin and Weismann, coupled 

 with an almost fanatical advocacy of the notion that organic evo- 

 lution depends upon the inheritance of acquired characters, was 

 enough to prejudice the whole case of orthogenesis. Moreover, the 

 controversial setting given to the idea of definitely directed varia- 

 tion, without the aid of utility and natural selection, made it difficult 

 to escape the conclusion that orthogenesis was only a new form of 

 the old teleology, from the paralyzing domination of which Darwin 

 and Lyell and their followers had rescued science. Thus handicapped, 

 the theory of orthogenesis has found little favor outside the circle 

 of Eimer's pupils. 



The second of the two theories alluded to is the mutation theory 

 of Hugo de Vries. The distinguished author of this theory, whose 

 presence honors this International Congress, and lends special eclat 

 to the Section of Phylogeny, maintains, on the basis of long-con- 

 tinued experimental research, that species originate, not by slow, 

 gradual variation, as held by Darwin and Wallace, but by sudden 

 saltations, or sport-like mutations. According to this theory, two 

 fundamentally distinct phenomena have hitherto been confounded 

 under the term variation. In other words, variation, as used by 



1 A name introduced by Wilhelm Haacke (Gestaltung und Vererbung, p. 31). 



