LAW OF SIMILARITY. 21 



CHAPTEE II. 



The Law of Similarity. 



The first and most important of the laws to be con- 

 sidered in this connection is that of Similarity. It is 

 by virtue of this law that the peculiar characters, qual- 

 ities and properties of the parents, whether external 

 or internal, good or bad, healthy or diseased, are trans- 

 mitted to their offspring. This is one of the plainest 

 and most certain of the laws of nature. Children 

 resemble their parents, and they do so because these 

 are hereditary. The law is constant. Within certain 

 limits progeny always and every where resemble their 

 parents. If this were not so, there would be no con- 

 stancy of species, and a horse might beget a calf or a 

 sow have a litter of puppies, which is never the case, — 

 for in all time we find repeated in the offspring the 

 structure, the instincts and all the general character- 

 istics of the parents, and never those of another species. 

 Such is the law of nature and hence the axiom that 

 "like produces like." But while experience teaches 

 the constancy of hereditary transmission, it teaches 

 just as plainly that the constancy is not absolute and 



