CHAPTER II. 



THE PROBLEM OF THE ORIGIN OF SPECIES. 1 



Among the rival theories of natural selection two are especially noteworthy. 

 One of these is now generally known as orthogenesis.- Theodore Eimer was one of 

 the early champions of this theory, basing his arguments primarily upon his re- 

 searches on the variation of the wall-lizard (1874-81). Eimer boldly announced 

 his later works on The Origin of Species (1888) and the Orthogenesis of the Butter- 

 flies (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 intemperate ferocity toward the views of Darwin 

 and Weismann, coupled with an equally intemperate advocacy of the notion that 

 organic evolution 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 variation, 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 maintains, on the basis of long- 

 continued 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 Darwin and others, covers two classes of phenomena, totally distinct 

 in nature, action, and effect. Variation proper is defined as the ordinary, fluc- 

 tuating, or individual variation, and this is held to be absolutely impotent to form 

 new species. 



It is claimed that no amount of either natural or artificial selection can by any 

 possibility lead this variation up to the birth of a new species. The utmost that 

 could be attained would be an improved race that would inevitably revert to the 

 original state as soon as left to itself. Mutation, on the other hand, never advances 

 by slow and minute modifications, which are continuous and cumulative, but by 

 single, sudden jumps. In the words of de Vries (vol. 1, page 150) : 



Species have not arisen through gradual selection, continued for hundreds or thousands 

 of years, but by jumps [stufenweise] through sudden, though small, transformations. In 

 contrast with variations which are changes advancing in a linear direction, the transfor- 

 mations to be called mutations diverge in new directions. They take place, then, so far 

 as experience goes, without definite direction. 



'An address before the Section of Phylogeny and reprinted from "Congress of Arts and Science, Universal 

 Exposition, St. Louis, 1904," Vol. V. A few introductory paragraphs have been omitted, and a very few minor addi- 

 tional changes have been made by the editor in adapting the address to this position in this volume. 



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



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