MIGRATION 



being re-sought. On the obscure point of the 

 origin of the migratory habit Dr. Eagle Clarke 

 finds the views of Russell Wallace and Weismann 

 largely confirmed. This opens out, however, 

 so wide a question, in which the survival of the 

 fittest is involved, that we cannot now enter upon 

 it. 



How ARE THE Migrants Guided ? 

 In dealing with this question, which he trul}' 

 describes as one of the greatest mysteries to be 

 found in the animal kingdom, Dr. Eagle Clarke 

 still proceeds on strictly scientific lines. One 

 by one he takes the various theories which have 

 been advanced, and tests each by the facts which 

 he has already ranged in ordered rows. 



Sight. 



The first in order is sight. It has been stated 

 that birds may possess some telescopic power of 

 vision, which goes far beyond anything man knows 

 of seeing. This, coupled with the admitted fact 

 that the main bodies of migrants attain to great 

 heights when travelling, and thus, with con- 

 tinents lying like a map, far below, landmarks 

 might be descried at what would at first appear 

 to be inconceivable distances, is held to account 

 for the true line achieved in steering. 



Against this explanation Dr. Eagle Clarke 

 sets the fact that most of the great migratory 

 movements take place at night, and it may be 

 said that, apart from the true nocturnal fowl, 

 there is not the faintest evidence that birds have 

 any specialised organs suited for night-vision : 

 indeed, all experience points to the contrary. 



If a finch or warbler, for example, be liberated 

 in a dark room, it will blunder helplessly to the 

 floor, unable to avail itself of the most obvious 

 perch : whereas experiment has shown that a bat 



75 



