MY NEW IDEAS 409 



odour of persons and furniture linger two months in the 

 streets ? " 



It is evident that at least twelve hours were occupied in 

 rinding the new place, leaving time for a good deal of trial 

 and error. One suggestion now occurs to me. There was a 

 rather circuitous omnibus route leading from Long Acre to 

 very near the new house. The dog may have often seen its 

 master travelling in a 'bus, and may even have gone with 

 some of the family. He may, therefore, have followed the 

 'bus route, seeking all the way for indications, till at last he 

 crossed the recent track of his master or of some other member 

 of the family, and by scent followed it up to the door. The 

 following passage concludes my letter to Nature : — 



" I venture to hope that some persons having means and 

 leisure will experiment on this subject in the same careful and 

 thorough way that Mr. Spalding experimented with his fowls. 

 The animal's previous history must be known and recorded ; a 

 sufficient number of experiments, at various distances and 

 under different conditions, must be made; and a person of 

 intelligence and activity must keep the animal in sight, and 

 note down its every action till it arrives home. If this is 

 done, I feel sure that a satisfactory theory will soon be arrived 

 at, and much of, if not all, the mystery that now attaches to 

 this class of facts be removed." This suggestion I have made 

 several times during the last thirty years, but I cannot learn 

 that any one has yet carried it out. It is strange that while 

 thousands of dogs' lives are sacrificed annually to establish 

 some minute point in physiology, no one can be found to carry 

 out a few pleasurable and interesting experiments to ascertain 

 in what manner and by the use of what faculties lost animals 

 habitually find their way home. 



An analogous problem to this is that of the migration of 

 birds, which also has been almost always imputed to some 

 special instinct or peculiar faculty other than that of the ordi- 

 nary senses. On this question I wrote to Nature as follows 

 (October 8, 1874) : " It appears to me probable that here, as 

 in so many other cases, ' survival of the fittest ' will be found 

 to have had a powerful influence. Let us suppose that with 



