Ix INTRODUCTION. 



liar conformation, may transmit the same properties of form 

 to their young, and these again to their descendants, has been 

 matter of observation in every age. The greyhound com- 

 municates to his progeny, the flexible neck, the long back, 

 the slender agile limbs, which fit him for capturing his prey 

 by speed ; the blood-hound transmits his expanded nostril, 

 fitted for that surpassing sense of smell which enables him 

 to follow the evanescent traces of his victim upon the ground ; 

 the bull-dog transmits to his young his muscular form and 

 powerful jaws. No one ever expects to see two greyhounds 

 produce an animal like a terrier ; two blood-hounds, one re- 

 sembling a shepherd's cur; two bull-dogs, any animal dif- 

 ferent in essential characters from themselves. And in all 

 those varieties of the other domesticated animals which we 

 term breeds, the constancy of the law of transmitted proper- 

 ties is alike manifested. The Merino sheep communicates to 

 its young the properties which it has acquired on the moun- 

 tain pastures of Spain, of producing a short unctuous wool, 

 and this in localities so different as in the granitic soils of 

 Sweden, the plains of Silesia, the sands of the Cape of Good 

 Hope, and the myrtle forests of New Holland. The Horse 

 of the Arabian deserts, wherever he is carried, communicates 

 to his descendants the properties distinctive of his race. The 

 great Black Horse of the meadows of Flanders transmits to 

 his progeny the massive form and very colour which he has 

 himself acquired ; the Race-Horse of England, the conforma- 

 tion which adapts him to rapid motion ; the Pony of Norway, 

 the characters which have fitted him for a country of heaths 

 and mountains : and so on in every case where animals, by 

 successive reproduction with one another, have acquired the 

 common properties which constitute a breed. 



In the human species, that similarity of features which is 

 termed family likeness, is a familiar example of the same 

 effect, not only manifesting itself in the immediate descend- 

 ants, but reappearing often after several generations. The 

 community of character which constitutes national resem- 



