Ixx INTRODUCTION. 



the other a lower range ; yet these sheep, though mingled in 

 the commons of the country for ages, preserve themselves 

 distinct ; and even the female of the Dog, if left free to 

 choose her mate, will almost always make the selection of 

 one of her own kind, a greyhound of a greyhound, a terrier 

 of a terrier, and so on. Were not some natural provision of 

 this kind made, we might expect to meet innumerable hy- 

 bridal animals in the state of nature ; for there can be no 

 reasonable doubt that many animals which we call distinct 

 species, are capable of breeding together, and producing a 

 fruitful offspring. 



II. PROPERTIES OF EXTERNAL FORM. 



The characters, in animals, of external form, may be com- 

 municated, it has been seen, from the parents to the young ; 

 and upon the constancy of this effect may be said to be 

 founded the whole principle of what is termed Breeding, 

 whether pursued to the degree of forming distinct varieties, 

 or of merely communicating to individuals the peculiar cha- 

 racters which we desire them to possess. If we would form 

 a variety or breed, we must select the animals possessed of 

 the characters sought for, and, by breeding from the progeny, 

 endeavour to give permanence to the characters acquired. 

 If we wish to procure individual Horses possessing the fa- 

 culty of speed, we unite in blood those which possess, in the 

 requisite degree, the form and properties which we seek to 

 reproduce in the progeny ; if we design to procure Horses 

 having the strength fitted for labour, and the exertion of their 

 powers in draught, we select the males and the females whose 

 external form indicates their adaptation to the uses required ; 

 if we are to propagate animals for the production of muscle 

 and fat, we choose for the parents those whose conformation 

 indicates the faculty of soon arriving at maturity, and readily 

 assimilating nourishment. 



