WEST COAST OP SCOTLAND. 71 



my firm belief that there is more in it than appeared on the 

 surface, and that the more we know of migration the more fully 

 will his theory be borne out. 



It is known to naturalists that some species which are known 

 to breed in the highest northern latitudes travel on migration to 

 the furthest southern localities. Let us instance the Knot 

 (Tringa canuta). Temperature has to do with this directly. 

 What a vast breeding-ground of this species, as yet undiscovered, 

 must there be somewhere in the far north if we witness the great 

 streams on their annual migration along our coasts. In spring 

 they travel on and on towards the north until they find a 

 temperature cool enough for the successful hatching and rearing 

 of their young, reaching their far off summer quarters even before 

 insect-life has begun to show itself, after the long Arctic winter ; 

 and, with the strength and vigour of a far northern-bred species, 

 they adapt themselves to the only food existing — the fronds of 

 lichen laid bare by the first melting of the snow. The hardiness 

 of the race, bred thus on the shores of the Arctic seas, induces 

 the vigour and "fitness" which enables them to travel so far 

 again to the southward in autumn and winter ; and it is the 

 annual overflow of their vast numbers, pressing behind those in 

 the van, which — as it were — adds impulse to the ability, and 

 carries them forward. They press forward in autumn to fresh 

 feeding-grounds as those behind are taken up by others suc- 

 ceeding them. 



