310 DARWINISM TO-DAY. 



bank's work, which has attracted so much attention from evolu- 

 tionists and the world generally, was published by Kellogg, in the 

 Pop. Sci., Mo., Vol. LXIX, pp. 363-374, 1906. 



"Mr. Burbank has so far not formulated any new or additional 

 laws of species-change, nor do his observations and results justify 



Scientific an ^ suc ^ formulation, and we may rest in the belief 



aspects of Bur- that he has no new fundamental laws to reveal. He 

 tank's work. h as indeed the right to formulate, if he cares to, some 

 valuable and significant special conclusions touching certain already 

 recognised evolution factors, in particular the influence on varia- 

 bility of the two long-known variation-producing factors of hybridi- 

 sation and modification of environment. His reliance on the marked 

 increase in variability to be got after a crossing in the second and 

 third generations over that obvious in the first, will come as a sur- 

 prise to most men first getting acquainted with his work. He has 

 got more starts for his new things from these generations than in 

 any other way. He is wholly clear and convinced in his own mind as 

 to the inheritance of acquired characters ; 'acquired characters are 

 inherited or I know nothing of plant life,' he says; and also con- 

 vinced that the only unit in organic nature is the individual, not 

 the species ; that the so-called species are wholly mutable and de- 

 pendent for their apparent fixity solely on the length of time through 

 which their so-called phyletic characters have been ontogenetically 

 repeated. He does not agree at all with de Vries that mutations in 

 plants occur only at certain periodic times in the history of the 

 species, but rather that, if they occur at all, they do so whenever 

 the special stimulus derived from unusual nutrition or general 

 environment can be brought to bear on them. He finds in his 

 breeding work no prepotency of either sex as such in inheritance, 

 though any character or group of characters may be prepotent in 

 either sex. He believes that no sharp line can be drawn between the 

 fluctuating or so-called Darwinian variations and those less usual, 

 large, discontinuous ones called sports. Ordinary fluctuating varia- 

 tion goes on under ordinary conditions of nutrition, but with ex- 

 traordinary environmental conditions come about extraordinary 

 variation results, namely, discontinuous, sport or mutational varia- 

 tion. These variations are the effects of past environment also, 

 having remained latent until opportunity for their development 

 occurs. Starvation causes reversions, but reversions can also be 

 produced by unusually rich nutrition. New variations are developed 

 most often, as far as environmental influences go, by rich soil and 

 generally favourable conditions. So-called new qualities are usually, 

 if not always (the fact may sometimes not be obvious), simply 

 new combinations of old qualities, both latent and obvious. To get 



