VARIATION. 



IN the foregoing chapters I have endeavored 

 to give a brief statement of the law of hered- 

 ity, and to illustrate the more important spe- 

 cial cases which occur under it. Even in the 

 discussion of the law and of its operation it was 

 evident that somewhere in Nature there was a 

 contrary force at work. What that is will now 

 be explained. 



If the law of heredity always operated with 

 perfect precision and equal force the results of 

 breeding would be simple, and could always 

 be expressed by a mathematical formula. But 

 we have already seen that the normal condi- 

 tion even is not an equal admixture of the pa- 

 rents' natures; that this is purely theoretical 

 and ideal. The force of heredity under what 

 may be termed, perhaps not inaccurately, ab- 

 normal circumstances, we have had illustrated 

 in the subordinate laws of atavism and prepo- 

 tency. The exceptions to the rule o^heredity, 

 the power of darkness warring against the law 

 of light, the world-born tendency of chaos in 

 open opposition to heaven-born law and ojder, 

 now require our attention. 



The fact that Nature sometimes departs from 



(61) 



