DEEPER PROBLEMS OF MIGRATION 295 



spot his own," we are not inclined to go beyond the hypo- 

 thesis of a visceral Heimweh. 



We must not press these considerations too hard, as if 

 living creatures were inert balls buffeted here and there by 

 sheer compulsion. The reasons we have given for the 

 autumnal and vernal movements are impelling rather 

 than compelling, they operate on constitutional pre- 

 dispositions. There are notable difficulties remaining, 

 and curious individual exceptions, such as that of the 

 cuckoo. Therefore let us turn for a moment, all unsatisfied 

 with explanations, to enjoy the mysteriousness of this 

 vital tide, agreeing with Gatke that " both phases of the 

 great movement unfold a picture of bird life of incom- 

 prehensible grandeur, presenting to our wondering sight 

 myriads of these restless wanderers hastening during the 

 long dark nights of Autumn, or the starlit midnight hours 

 of Spring, by many intersecting paths, to their far-off 

 Winter quarters or their nesting homes ; each species 

 following, at higher or lower regions in the sky, a sure 

 and definite road, not marked out for them along river 

 courses or mountain chains, but one that leads them, 

 independent of every physical configuration of the earth's 

 surface, and at heights many thousands of feet above it, 

 surely and safely to the distant goal." 



This brings us to the question, How do the birds find 

 their way ? It is our strong conviction that before natural- 

 ists will make much of a question of this degree of difficulty 

 there will require to be many years of hard work at much 

 less exciting questions, such as What way do they find? 

 At the same time, it is very interesting to raise the very 

 difficult question of way-finding, and to consider the sug- 

 gestions that have been offered. 



" Who calls the council, states the certain day, 

 Who forms the phalanx, and who leads the way ? " 



