PRESENT STATUS OF THE QUESTION 23 



theory. This distinction was between variations, 

 on the one hand, and mutations, on the other. By 

 variations, Waagen understood the fluctuating dif- 

 ferences between contemporary individuals of the 

 same species, differences which are repeated in every 

 generation and are entirely inconstant. Mutations 

 are successive changes, which, however slight they 

 may be, are yet constant in character, and a series of 

 mutations forms successive connected steps of modi- 

 fication in a definite direction. The eminent Dutch 

 botanist de Vries adopted this conception and, with 

 certain changes, erected it into an elaborate theory, 

 which has formed the subject of much controversy. 

 De Vries points out that Darwin did not distinguish 

 clearly between the two kinds of modifications which 

 have, or may have, furnished the starting-points for 

 the various races and breeds of domesticated animals 

 and plants. One kind is the ordinary difference 

 between individuals and the other is the "sport," or 

 sudden and notable change in one or more charac- 

 teristics, a change which is constant and transmis- 

 sible to the offspring. An often cited "sport" is the 

 Ancon sheep, a breed which arose from a single 

 short-legged ram, born of normal parents in 1791 on 

 a New Hampshire farm. This ram transmitted his 

 peculiarities to his descendants and soon a new kind 

 of sheep, popular because of their inability to jump 

 fences, was established. Such a sudden, unheralded 

 and transmissible change of structure de Vries calls 

 a mutation and he believes that mutation is the 



