192 ON THE ORIGIN OF SPECIES 



actions differ essentially from true instincts. If we 

 were to see one kind of wolf, when young and without 

 any training, as soon as it scented its prey, stand 

 motionless like a statue, and then slowly crawl forward 

 with a peculiar gait ; and another kind of wolf rushing 

 round, instead of at, a herd of deer, and driving them 

 to a distant point, we should assuredly call these actions 

 instinctive. Domestic instincts, as they may be called, 

 are certainly far less fixed or invariable than natural 

 instincts ; but they have been acted on 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 

 dispositions 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 grey- 

 hound has given to a whole family of shepherd-dogs a 

 tendency to hunt hares. These domestic instincts, 

 when thus tested by crossing, resemble natural instincts, 

 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 compulsory habit, but this, I think, 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 witnessed, is per- 

 formed 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 generations made tumblers what they now 

 are ; and near Glasgow there are house -tumblers, as I 



