142 



THE BIKDS OF HELIGOLAND 



east of Heligoland. Now, in this case the causes which determined 

 the movement were of a quite different nature from those concerned 

 in the normal autumn migration, which takes place at a time when 

 there is not as yet the least indication of frost or snow. Neverthe- 

 less, the birds managed to hit upon the right way of escaping from 

 this sudden and strange emergency. Moreover, in these abnormal 

 circumstances they acted as, indeed, they do in all their regular 

 migratory movements as though they were fully conscious of the 

 causes which lay at the origin of the movement, and of the pur- 

 pose they had in view. Nay, more, they seemed as though they 

 were endowed with an intelligence capable of surmounting all 

 obstacles which might tend to hinder their normal course of action. 

 Therefore, if neither the theory of hereditary transmission, nor that 

 of teaching handed down from one generation to the next, is able 

 to explain the ordinary phenomena of migration, how much more 

 do these theories fall short of throwing light on exceptional in- 

 stances such as that just related ! 



Having thus examined the many various attempts made to 

 explain the wonderful faculty possessed by migrants of discovering 

 the right path of their migration, and shown how insufficient most 

 of them are when confronted with actual facts, observed directly in 

 nature, in the course of more than fifty years' investigations and at 

 a spot so favoured as Heligoland, I cannot say that I feel encouraged 

 to add further to the number of such attempts by others of my 

 own. 



