Heredity 57 



heredity by which the offspring is patterned after the parent. 

 This law is still a mystery in its workings, but its effects are 

 well known. The effect upon one generation, of weeding 

 out of weaklings as above noted, would perhaps be small, 

 but when the same process is repeated generation after 

 generation that effect accumulates rapidly. 



This fact is well known to breeders and fanciers of fowls 

 who are able to take peculiar individuals, such for example 

 as those of a special coloring, and by accumulating the 

 selection through many generations to make it pronounced 

 and fixed. This is easily understood. It is however a little 

 more difficult to comprehend that every form in existence, 

 and every capacity, and every habit of life is originally the 

 result of a building up of such small acquirements. Yet 

 this is the fact and it must be realized. The principle of 

 heredity not only takes care of the transmission of the 

 recently fixed things; but it is the director of the oldest of 

 the old characters. Therefore the constancy in type of the 

 whole bodily structure of any animal is due to heredity. 

 For example, a horse always possesses hoofs, which are 

 practically single-toed feet; it never is found with five-toed 

 feet, with claws like a tiger's. Yet the five-toed form is 

 just as usual in nature. And similarly each part of an 

 animal's equipment, body and limbs or wings, and lungs, 

 or gills, or whatever they may be, are always proper ac- 

 cording to the equipment of its ancestry. All this seems to 

 be necessarily so, but that seeming is only because it is con- 

 stantly so. Why should not horses be born with five-toed 

 feet with claws or with two or five legs? Trees of any 

 species grow with varying number of branches, one with 



