372 The Outline of Science 



connected with the type of the species by intermediate gradations. 

 We may think of the white crow or the weeping willow. The 

 Proteus leaps as well as creeps. Especially through the investi- 

 gations of Professor William Bateson and Professor Hugo de 

 Vries, it has become plain that changes of considerable magni- 

 tude may occur at a bound. When the new character that sud- 

 denly appears, such as a Shirley Poppy or a short-legged Ancon 

 Sheep, has a considerable degree of perfection from its first 

 appearance, is independently heritable to the offspring, and does 

 not blend or average off, it is called a Mutation. Professor de 

 Vries writes : "The current belief assumes that species are slowly 

 changed into new types. In contradiction to this conception the 

 theory of mutation assumes that new species and varieties are 

 produced from existing forms by sudden leaps. The parent type 

 itself remains unchanged throughout the process, and may repeat- 

 edly give birth to new forms. These may arise simultaneously 

 and in groups, or separately at more or less widely distant 

 periods." This was strikingly illustrated by the sporting Even- 

 ing Primrose (CEnothera lamarckiana) , a species of North Amer- 

 ican origin, which de Vries found at Hilversum in Holland, and 

 which proved to be in a very changeful mood. Almost all its 

 organs were varying, as if swayed by a restless internal tide. It 

 gave rise abruptly to numerous new forms which bred true. It 

 illustrated species in the making. 



Darwin found the raw material of evolution in small fluctu- 

 ating variations, which are no doubt of frequent occurrence. 

 Since Darwin's day it has become not only possible but neces- 

 sary to attach much importance to discontinuous mutations. The 

 contrast was aptly illustrated by Sir Francis Galton, who com- 

 pared the varying organism to a polyhedron (a solid body with 

 many faces) which can roll from one face to another. When it 

 settles down on any particular face it is in stable equilibrium. 

 Small disturbances may make the polyhedron oscillate, but it 

 always returns to the same face. These oscillations are like 



