268 ORIGIN OF SPECIES 



by far less rigorous selection, and have been transmitted for 

 an incomparably shorter period, under less fixed conditions 

 of life. 



How strongly these domestic instincts, habits, and disposi- 

 tions are inherited, and how curiously they become mingled, 

 is well shown when different breeds of dogs are crossed. 

 Thus it is known that a cross with a bull-dog has affected for 

 many generations the courage and obstinacy of greyhounds; 

 and a cross with a greyhound has given to a whole family of 

 shepherd-dogs a tendency to hunt hares. These domestic in- 

 stincts, when thus tested by crossing, resemble natural in- 

 stincts, which in a like manner become curiously blended 

 together, and for a long period exhibit traces of the instincts 

 of either parent: for example, Le Roy describes a dog, whose 

 great-grandfather was a wolf, and this dog showed a trace 

 of its wild parentage only in one way, by not coming in a 

 straight line to his master, when called. 



Domestic instincts are sometimes spoken of as actions which 

 have become inherited solely from long-continued and com- 

 pulsory habit; but this is not true. No one would ever have 

 thought of teaching, or probably could have taught, the 

 tumbler-pigeon to tumble, — an action which, as I have wit- 

 nessed, is performed by young birds, that have never seen a 

 pigeon tumble. We may believe that some one pigeon showed 

 a slight tendency to this strange habit, and that the long- 

 continued selection of the best individuals in successive gen- 

 erations made tumblers what they now are ; and near Glasgow 

 there are house-tumblers, as I hear from Mr. Brent, which 

 cannot fly eighteen inches high without going head over 

 heels. It may be doubted whether any one would have 

 thought of training a dog to point, had not some one dog 

 naturally shown a tendency in this line; and this is known 

 occasionally to happen, as I once saw, in a pure terrier: the 

 act of pointing is probably, as many have thought, only the 

 exaggerated pause of an animal preparing to spring on its 

 prey. When the first tendency to point was once displayed, 

 methodical selection and the inherited effects of compulsory 

 training in each successive generation would soon complete 

 the work; and unconscious selection is still in progress, as 

 each man tries to procure, without intending to improve the 



