Variations and Adaptations in Animals and Plants 727 



above two cases, one cannot consider either one by itself, but in all prob- 

 ability the two working together would explain the causes of variations 

 in a majority of cases. However, at one time the major or originating 

 force might be external, while at another it might be internal. August 

 Weismann believed that the causes of variations, at least the heritable 

 ones, were inborn or intrinsic in the germ plasm. He suggested that sex- 

 ual reproduction was for the purpose of mingling two strains of germ 

 plasm, thereby doubling the possibilities of variations. Bateson sug- 

 gested the futility of attempting to guess at the causes of variations, 

 especially in the light of our present profound ignorance in this direction. 



RESULTS OF VARIATIONS 



Reflection will suggest many and varied results of variations. A few 

 of the more important effects might be listed as follows: (1) Improve- 

 ment of a race of animals and plants is possible by taking advantage of 

 variations within them. (2) Through variations, individualities of or- 

 ganisms can be expressed. (3) With variations always present it is 

 difficult to maintain pure lines or standard types. (4) The presence of 

 variations provides for the diversification of species so that at least some 

 of the individuals may be better fitted to cope with their environments, 

 especially should the latter change, as they constantly are doing. Since, 

 environments are always varying, it is necessary that organisms vary also 

 in order efficiently and harmoniously to fit into their environments. (5) 

 Variations furnish valuable materials for the study of genetics. Without 

 variations, the science of genetics would be much simpler and more easily 

 understood. (6) Variations produce the "spice of life," for without 

 them all organisms would produce such similarities that there would be 

 few changes and all things always would be the same. (7) Education is 

 based on variations. Without the possibility or ability of producing 

 variations, attempts at education would be unnecessary and impossible. 

 Through this process, the hereditary materials of an individual are sub- 

 jected to the educational or environmental stimuli, thus bringing out and 

 retaining such varieties of abilities as distinguish us one from another. 

 Would it be desirable to have all individuals of equal ability, even though 

 that ability might be high? Can two individuals really be equal? 



ADAPTATIONS 



Adaptations might be considered to be the result of those variations 

 which are advantageous and enable an organism to live more success- 

 fully in its environment and in its struggle for existence (Fig. 361). 



