CONDITIONS OF DEVELOPMENT. 247 



of nations. In regard to individuals also, we notice 

 that the great stress of social and political crises pro- 

 duces great men ; and lives filled with many events 

 and strong and varied emotions produce the great- 

 est characters. The greater the strength and variety 

 of the stimuli have been, the greater has been the 

 resulting progress of development, — provided the 

 stimuli did not pass the limit beyond which they 

 become destructive. 



When we extend the application of this last con- 

 clusion to the physical development of organisms, 

 it is found to explain a peculiar phenomenon. It 

 has been observed that the human race, under the 

 strenuous conditions of life existing in newly settled 

 countries, shows a higher birth rate of males than 

 of females, while in the easier conditions of older 

 countries the opposite is the case. The male or- 

 ganism is — from a morphological point of view — 

 a more advanced or specialised development than 

 the female, and the conclusion is easily drawn, that 

 the stronger stimuli of the life in a new country 

 cause greater activity of the vital forces in the 

 parents, which expresses itself in the production of 

 the more specialised sex. So the production of 

 females may be regarded as a form of atavism in- 

 duced in easy circumstances by the relaxation of 

 the stimuli of life. In the same way, among, many 



