MENDELISM AND OTHER METHODS OF DESCENT 233 



" Thence we must conclude that new species are produced 

 sideways by other forms, and that this change only affects the 

 product, and not the producer." ' 



But if a new variation can arise suddenly and persist without 

 isolation as a character of its species, the producer is changed 

 as well as the product. Indeed, the new variation does not 

 gain or maintain its existence as a separate product, but merely 

 increases the diversity of the parent group. 



Spontaneous transformation of species by the prepotency of 

 new variations, under natural conditions of wide distribution 

 and free interbreeding, is the method of developmental progress 

 outlined in what has been called the kinetic theory of evolution. 

 Previous theories had not recognized the possibilities of direct 

 and spontaneous accumulation of new variations. Usually they 

 had sought the agencies of evolution in the isolation of varia- 

 tions by selection or in other forms of environmental interfer- 

 ence with an ideal condition of uniformity and stability. The 

 mutation theory of De Vries reasserts this uniformity and sta- 

 bility as the moral condition of species, and seeks to explain 

 evolutionary progress by sudden leaps from one species into 

 another, and not by any gradual change, through prepotency 



■^De Vries, H., 1905. The Evidence of Evolution. Smithsonian Report for 

 1904, p. 396. 



An even more detailed and explicit denial of any gradual transformation of 

 species is contained in a paper by Professor De Vries in the Monist for January, 

 1907. 



" The conception of mutations agrees with the old view of the constancy of 

 species. This theory assumes that each species has its birth, its life-time and 

 its death even as an individual, and that throughout its life it remains one and 

 the same. Thus it is only natural that wild species are almost always observed 

 to be constant, since by a mutation they do not change themselves but simply 

 produce a new type. This is allied to its ancestor as a branch is to a tree, the 

 stem continuing its own growth, no matter how many branches it produces. 

 Just so a species may produce quite a number of neV forms without being 

 changed itself in the least thereby. Among palaeontologists Scott has given 

 forth this same view. According to his conception, species are derived from 

 one another by small shocks. Each shock caused the old limits to be trans- 

 gressed ; but, after it, the new species remained unchanged until, perhaps after 

 centuries, a new shock made it transgress its new limits. Each single type (be 

 it species, subspecies or variety) is thus wholly constant from its first appear- 

 ance and until the time it disappears, either after, or without, the production of 

 daughter-species." 



