AMERICAN INSTITUTE. 493 



the peculiarities of the one race are lost in the other. So tliere is 

 no race of mulattoes on the face of the earth permanent — the ten- 

 dency being to rim into one or other parent race. The same law 

 holds good throughout all nature — hybrid forms being transient, 

 because they are more fruitful with either parent stock, as a ball 

 rolling along a ridge has its progress accelerated by leaving it in 

 either direction. 



As we have seen the variations in any species to be dependent 

 on the different qualities of the food, so we shall find that the va- 

 riations are greater in those species that may live and thrive on 

 the most different food. Thus, the common fowl being omnivor- 

 ous inhabits all climates and assumes almost all shapes. While 

 the American partridge which can only subsist on certain buds is 

 limited in locality because it is poisoned by corn. The dog being 

 almost equally omnivorous with man, accompanies him in all 

 climates. Swine accompany him every where except in the ex- 

 treme polar zones, because they are equally omnivorous. It is 

 probable they would go to the very pole with man if equally pro- 

 tected. The cat having a less accomodating stomach confines her- 

 self more to the house, the region of artificial climate, and is yet 

 more limited in range. The horse and ox, graminivorous only and 

 unable to obtain the advantages of the fire are more limited than 

 man in their range. -Rats and mice equally omnivorous accom- 

 pany him wherever they may surreptitiously obtain advantage of 

 the artificial climate he makes. 



Of these different species the dog is the one that has the greatest 

 range, and he is the one that undergoes the greatest variations, 

 being so small in some races as hardly to weigh two pounds, and 

 large enough in others to weigh an hundred. Though not strictly 

 necessary to our conclusions yet in confirmation of them, we shall 

 find that those species that vary most in size are those that may 

 vary most in distribution. 



Though man provides for himself an artificial climate to which 

 he may resort at will, and protects himself from extremes of tem- 

 perature by clothing, yet when he migrates he must make a change 

 in his food to meet his altered necessities. Thus Dr. Kane and 

 his company to meet the demands of the polar climate for animal 



