THE LESSON OF HEREDITY 



example. Even as you observe it beneath the micro- 

 scope, it divides, and two bacilli are there in place of 

 one. This process it will continue indefinitely, under 

 proper conditions, until there are myriads of bacilli 

 there, but every one will be precisely like the first. The 

 cholera bacillus never changes into the bacillus of con- 

 sumption, nor that into the bacillus of diphtheria. 

 Each produces its own kind and no other. 'Like 

 begets like!' It is beautifully simple, unequivocally 

 true, and of universal application." 



It is little wonder that so relatively simple, so true 

 and so sweeping a proposition has proved alluring. 

 All universal formulae are so. But it should not be 

 forgotten that a seemingly simple principle may become 

 very complex indeed, in its application. So it is here. 

 Indeed, a stumbling-block of most alarming dimen- 

 sions appears at the very outset if we attempt to apply 

 the principle of heredity intelligently to any higher 

 organism, in the fact that two parents are to be con- 

 sidered. These parents are not precisely like one an- 

 other, hence, in the nature of the case, the offspring 

 must be either identical with one parent and unlike 

 the other, or else identical with neither. Here theory 

 wavers, but experience proves that the offspring always 

 combines in some measure the qualities of both parents; 

 hence, that it never is precisely like either of them. 

 What, then, becomes of the principle of heredity? It 

 appears that like does not beget like in the sense of 

 identity; and if "like" is only meant to convey a sense 

 of general similarity, it is altogether too vague a prin- 

 ciple to have practical utility. 



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