ioo THE THEORY OF MUTATIONS 



as it would be on the Darwinian theory, but that, 

 as Dwight points out,* " it implies the existence 

 of a type and of a law which under certain condit- 

 ions becomes operative." 



I shall have to refer further to this matter at 

 the end of this article, and will therefore pass to 

 two other points of great importance which come 

 into direct bearing with the question of mutations. 



In the first place one of the great difficulties 

 which has always stood in the way of the accept- 

 ance of the transformist doctrine has been the 

 inadequacy of the time which seems to have been 

 at the disposal of the world for the process. On 

 this point physicists and evolutionists have always 

 been at issue since Lord Kelvin made public his 

 views as to the age of the earth, the biologists de- 

 manding, for the operations which they supposed 

 to have taken place, a length of time which the 

 physicists were quite unwilling to concede. Now 

 it is obvious that if the process of transformation 

 can be shown to have taken place by great and 

 sudden changes, the difficulty here alluded to 

 very largely disappears. A comparatively short 

 time might suffice for the accomplishment of 

 changes through mutations, which would require 

 untold aeons if they were to take place through the 

 slow accumulation of small variations. 



In the next place the question of the geological 

 record is very much simplified. When the Dar- 

 winian hypothesis was first made public, the com- 

 mon argument urged against it was the fact that 

 as a matter of experience, the links which were 



t Science, N.S. xxi, 529. 



