PHENOMENA AND PRINCIPLES OF BREEDING 461 



or grade of character) cannot be transmitted is absurd. On the 

 other hand his experience teaches him that they are not regularly 

 and uniformly transmitted, even under the most uniform and favor- 

 able conditions, and that differences in forms compared at maturity 

 are due in part to environment and conditions affecting the creature 

 during its independent development, and in part to modifying ten- 

 dencies or to factors brought over or inherited from the parent 

 organism. The nature of these will appear as the phases of inher- 

 itance are presented. 



Beginning of variation. In the simpler forms of animal life, 

 variation through the influence of environment is plainly a cause 

 of individual differences. Such differences are evidently acquired 

 and as evidently transmitted, for, once separated, the parts may 

 become in a measure unlike through difference of environment. 

 One may die by accident or through lack of nourishment ; another, 

 more favorably placed than before, may grow larger than the parent 

 organism and in self-division produce creatures superior to what 

 it was at the beginning of its independent existence. Between 

 such extremes there is a range of possibilities of development, and 

 always, as long as the parts are equal at division, we can hardly con- 

 ceive of one possessing at its origin a characteristic that the other 

 has not. In the higher animal forms, with the germ developing 

 during a long period independently of the parent body, it is obvious 

 that, since environment may influence growth, there is opportunity 

 for much greater modification of the organism during the period 

 of development, and that, the more highly developed and specialized 

 the organism, and the greater its possibilities of somatic variation, 

 the more detrimental to the species it would be to have individual 

 variations fully and uniformly transmitted. Every slight variation 

 would start development in a new direction and there would be no 

 stability in animal forms. 



Sex the natural regulator of variation. As long as an organ- 

 ism reproduces independently, by simple self-division or by divi- 

 sion and combination of its own elements, its characters will be 

 reproduced in its offspring, and its tendencies intensified in each 

 succeeding generation developed under favorable conditions. 

 While simplicity of structure prevents wide variations, this is no 

 detriment and may be an advantage to the species. But as the 



