114 Dynamic Theory. 



The law of organic existence necessarily involves a perpetual selective 

 struggle. The existence of no organism is possible except on condition 

 of the destruction of some other organism or the repression of some 

 other organic possibility. The selection made necessary by the nature 

 of things is influenced by every circumstance in the environment either 

 directly or indirectly. The slightest difference between two animals 

 might determine the question of the survival of one or the other, such 

 for example as the thickness and warmth of the hair or fur covering, 

 which in an unusually cold winter might in one case be just sufficient to 

 save its owner from freezing, in the other, not. A shade or two differ- 

 ence in color might operate the same way, since the least conspicuous of 

 two beasts of prey could get nearer to his victim without being observed. 

 And on the other hand the most conspicuous victim would be the first 

 to be caught. 



Darwin observes that while it is easy to tame an animal it is exceed- 

 ingly difficult to get it to breed under confinement. This is especially 

 true of carnivorous birds. The same rule holds with regard to plants. 

 Taken from a natural state and subjected to cultivation, at first although 

 they grow with vigor, they refuse to bear seed. When civilization is 

 too suddenly imposed upon savages we see the same effect in the reduc- 

 tion of their breeding powers. The Sandwich Islanders and native New 

 Zealanders are conspicuous examples, and are being rapidly civilized 

 out of existence. It has been assumed sometimes that the decrease of 

 these populations was due to the introduction and prevalence of civilized 

 diseases and vices which carry them off but better information shows 

 it to be due to the decrease of the birth rate. 



The imposition of so-called "culture " upon civilized communities ap- 

 pears to have the same effect of reducing fertility and lowering the birth 

 rate in the cultured class ; so much so that its perpetuation depends on 

 constant reinforcements from the ranks of the uncultured classes. In 

 these cases there are introduced into the environment new stimuli which 

 do not find in the organization any corresponding anatomical (including 

 cerebral) differentiation from which these stimuli are reflected as a mat- 

 ter of use and habit. Consequently these stimuli act by exercising an 

 unusual degree of differentiating or developing influence, causing a con- 

 tinuous growth in the organism. It will be shown hereafter that a 

 checking or cessation of growth more or less complete in other direc- 

 tions is essential to the precipitation of vital energy in the form of re- 

 productive force. It further illustrates what has already been men- 

 tioned that every new feature of a changed environment begins to work 

 out new features in the organism and where worked out too fast tends 

 to exterminate that organism. 



