"W THE NEW EVOLUTION 



Biologically considered, all changes in environment 

 are strictly comparable whether they be brought 

 about by geological processes affecting large areas, 

 or by domestication affecting relatively small groups 

 of individuals. 



Furthermore, there is no tangible difference betw^een 

 the natural elimination, by the agency of enemies or 

 through disease or other causes, of all the individuals 

 of a certain type of w^olf which are unfitted to cope with 

 their environment, and the development of a special 

 breed of domesticated dog through the elimination of 

 all the individuals that do not come up to the standard 

 set by the dog breeder. 



To say that the evolutionary plan which is illus- 

 trated by the dogs is not comparable with the evolu- 

 tionary trees evidenced by the fossil animals is to deny 

 a similar effect as the result of similar causes. If, 

 however, we admit the validity of the comparison, 

 we at the same time admit the natural occurrence of 

 broad and striking gaps or discontinuities in evolu- 

 tionary lines. 



Unbroken continuity of descent coupled with 

 abrupt discontinuity or change in bodily form is a 

 common, striking, and well known phenomenon in 

 all types of animal life. It is far more striking among 

 the invertebrates than it is among the vertebrates. 



[i88] 



