A DORSET DIARY 141 



many more that die, an economy followed by nature 

 among the higher animals. This may be conjectm-al, 

 but, at any rate, the swallow must have learned some- 

 thing ; and the lingering thoughtlessly on into the 

 sudden peril of violent tempest with its holocaust of 

 lives must have been in some measure abated or par- 

 tially counteracted by some fresh stride of the swallow 

 mind, some original adaptability to meet the stress of 

 conditions making for failure of racial continuity.^ 



Originally, no doubt, migration was a " mutation," 

 that is to say, a brilliant idea, a creative inspiration, 

 a stroke of genius in precisely the sense we apply those 

 terms to the poet and the artist, born by the mysterious 

 ferment of the germ-cells both in rhythmic obedience 

 to the tidal sway of seasonal ebb and flow and to 

 battle with the pressure of unfavourable external con- 

 ditions (congestion of numbers, inadequate food-supply, 

 change of climate and so on). Then Natural Selection 

 got to work and sifted out the failing heart, the 

 dragging wing, the bewildered sense of direction, on 

 the one hand, while the active, enterprising, plastic 

 organism embodied the idea in perfect workmanship 

 through successive generations on the other — again 

 on the analogy of a poet giving form to a lyrical im- 

 pulse. Thus the success of the golden plover wintering 

 in the Hawaian and breeding in the Aleutian Islands 

 — a distance of two thousand miles — may be justly 

 compared with a poem that has " come off." The 

 mutation which gave birth to the sublime notion of 

 migration has become of course an instinctive inherit- 

 ance, but it has to be worked out by the individual 

 organism in its social relations, as the details of an 

 institution have to be worked out. I do not mean that 



^ Gatke's obervations of the migration of birds over Heligoland 

 afford pretty convincing evidence that the greater number of 

 the migrants fly from one to three miles high, and so would 

 become more or less superior to weather conditions. But that 

 does not alter the fact that (1) this occurs chiefly in windless 

 weather, and in bad the birds fly much lower, (2) that vast numbers 

 do not attain these elevations as the " rushes " at lighthouses 

 show. 



