THE STRUGGLE FOE EXISTENCE 37 



organism, and are thus enabled by degrees to reach, the 

 fully adaptive level. Natural selection cuts off the un- 

 adapted individual. The plastic individual though orig- 

 inally unadapted to its particular environment, may be 

 modified in such a manner that it survives. Of its off- 

 spring those who are plastic and adaptable survive, all 

 others perish. But if one among its offspring possesses 

 a germinal variation which better adapts it to the sur- 

 rounding conditions, it immediately has an advantage in 

 the struggle, and its progeny will inherit the favorable 

 quality. These offspring which possess an innate adap- 

 tation will have a much better chance for longer life and 

 larger families than those which possess mere plastic 

 modifiability. In this way, during the evolution of life 

 from low to higher and higher forms, Nature has weeded 

 out and exterminated the ill-adapted organisms, tolerat- 

 ing the temporary compromise of modification until the 

 progress of reproduction shall give rise to a real ger- 

 minal variation (mutation) which brings renewed stabil- 

 ity to the species. 



SUPPLEMENTARY READINGS. 



BOAS, F. The Mind of Primitive Man. 



CRAMPTON, H. E. The Doctrine of Evolution. 



DARWIN, C. The Origin of the Species. 



DAVENPORT, C. B. Heredity in Relation to Eugenics. 



GALTON, F. Natural Inheritance. 



KELLICOTT, W. E. The Social Direction of Human Evolution. 



METCALF, M. M. Organic Evolution. 



PUNNETT, R. C. Mendelism. 



Since modifications do not seem to be inherited, it follows that the only 

 kind of variations which count in the offspring are germinal variations. 

 Mutations or stable variations are germinal variations and are therefore of 

 more importance in evolution than fluctuating or unstable variations which 

 are not transmitted to offspring. See Metcalf, pp. 82-86. 



