HYBRIDS. 339 



homy excrescences on the human body, even though 

 they grow on the face, as they have done in some 

 instances, are just as truly human nails as if they 

 were on the fingers or the toes. In the case of hy- 

 brids, too, whether of plants or of animals, and in 

 the latter whether of quadrupeds or birds we know 

 little or nothing of hybrids among the other tribes, 

 though there may be instances in them there is a 

 law of nature that maintains the species. The 

 mules, of whatever they are hybrids, will not breed 

 as a race, though they generally can with either of 

 the parent stocks, and the result is a partial return to 

 that stock ; and if the system were continued, the 

 ultimate progeny would be again assimilated or 

 identified with the pure blood. 



Thus we can, with very little reflection, get hold 

 of the general principles that are to guide us in our 

 observation of animated nature. There is a specific 

 form handed down from race to race ; and the gen- 

 eral characters of that form cannot, be altered so 

 that one species shall resemble or merge into 

 another. This character is in the embryo, even 

 when that is too minute for being in any way the 

 subject of observation. That keeps them all true to 

 their kinds in the general way, so that we never find 

 a cat taking to the water and fishing at the bottom, 

 as an otter does, or a fish coming on land to hunt 

 for worms. As little do we ever find a hawk rob- 

 bing orchards, or a pigeon killing sparrows for food 

 to its young. 



But it is the general character only which descends 

 by hereditary succession. When the young leaves 

 the parent, and becomes an independent being, it is 

 controlled by circumstances, and must accommodate 

 itself to them. Thus, in proportion as the treatment 

 varies, the individual character must vary ; and that 

 is the reason why cultivated plants and animals are 

 so much more varied, in all their species, than wild 

 ones. The wild ones have only the changes of the 



