DISPERSAL AND MIGRATIONS 167 



mystery of Migration might be thought to come 

 in. This portion of the subject at all events is 

 surrounded by much unnecessary mystery, and 

 agencies have been invoked, even by scientific 

 naturaHsts, to account for this seeming wonder- 

 ful power of birds to pass from place to place 

 apparently unguided. Birds have been said to 

 possess a mysterious sense of direction, an in- 

 herited but unconscious experience. Other 

 naturalists have come to the conclusion that 

 birds possess an inner magnetic sense, by which 

 they are not only guided but able to ascertain 

 their position in relation to the m.agnetic poles. 

 The performance of the Homing or Carrier 

 Pigeon has been brought forward to prove that 

 birds possess an inherited sense of direction. 

 But the facts of the case, instead of supporting 

 the assertion, directly refute it. These Pigeons 

 have to undergo a careful course of training 

 before they are able to fly from one distant 

 place to another ; that is to say, they have to 

 be taught the way in a series of stages until 

 they have learnt the topography of the route. 

 If this be obscured by fog the birds will not 

 attempt the task, or doing so soon lose their 

 way. They fly by sight, aided by a very reten- 

 tive memory for certain landmarks. Another 



