14 A STUDY IN HEREDITY 



that this acquirement, being transmitted and in- 

 creased in subsequent generations, resulted in 

 evolution. Neo- Darwinians, on the other hand, 

 contend that the change was due solely to the 

 survival of those individuals which had naturally 

 the longer necks. They suppose that in times of 

 drought, when food was scarce, the shorter giraffes 

 perished, because they were less able than the taller 

 to reach the higher leaves of trees. The taller thus 

 alone continued the race, and this process, repeated 

 during long ages and many generations, resulted in 

 the long neck of the modern animal. Lamarckians 

 believe that hares run swiftly because their efforts at 

 swift running developed the appropriate structures, 

 and this improvement, transmitted and increased 

 generation after generation, resulted at last in that 

 very swift animal the modern hare. Neo-Darwinians 

 contend that the great speed of hares is due to 

 the fact that those animals who were naturally 

 the swiftest escaped their enemies, and that by 

 this means, during the process of ages, was the 

 swift modern hare evolved. Say they, all animals 

 other than giraffes also stretched upwards for food, 

 yet their necks did not grow long ; all animals 

 other than hares strove to run fast, yet they did 

 not become so speedy. On the contrary, their 

 survival was secured by evolving in other direc- 

 tions. Lamarckians assert, but Neo-Darwinians 



