INSTINCT AND REASON. 63 



but tliey went on building them all in the same 

 way until at last every bird of each kind inherits 

 at l)irth the nest-making faculty exactly as it in- 

 herits wings to fly and feet to perch with. So, 

 too, the swallows may have convinced themselves 

 by slow experience of the advantages of migrat- 

 ing and the ants may have gradually acquired the 

 habit of foraging in regular parties along fixed 

 highways. We know, indeed, that the retriever 

 has been regularly taught to retrieve and the ter- 

 rier to worry ; yet so instinctive have those two 

 habits now become in the two breeds that, if you 

 throw a handkerchief down to a young retriever 

 puppy, he will bring it over and lay it at your 

 feet as if it were a game-bird ; while if you throw 

 it to a baby terrier, he will shake it in his teeth 

 savagely, as if it were a rat. Sheep in Spain are _^ ^., 

 driven every year by their owners from the parched 

 lowlands to the mountain pastures; and in the 

 course of generations this acquired habit of mi- j 

 grating has become so ingrained in the very brains * 

 of the merinos that as the time for movijig aj)- / 

 proaches they begin to exhibit uneasy feelings ex- / 

 actly like those of wild geese or other migratory I 

 birds at the advent of the season for the annual ( 

 flight. It is not improbable, therefore, that instinct 

 is in many, if not in most, cases a form of hq)sed 

 or organized intelligence — a result of what were 

 once reasonable inferences from experience acting 



