SEASONAL LIFE 83 



as the former is, save for its darker hue, inclistini;uishable from 

 the Common Short-eared Owl {As/o brachyotiis), a bird which 

 ranges over well-nigh the whole world, and is known in Great 

 Britain as the Woodcock Owl, while the Night-heron is 

 similarly only distinguished from the South American Violaceus 

 Night-heron (A', violaceus). 



Mr. J. A. Allen has brought to light some extremely 

 interesting facts with regard to the relation between changes 

 of colour and meteorological conditions. An intensity of 

 pigmentation occurs, he points out, with regard to American 

 animals, from North to South, coinciding with the intensity of 

 the sun's rays and the increase of humidity. The increase in 

 colour observed in birds on passing from East to West points 

 to the same factors, " the darker representatives of any species 

 occurring where the annual rainfall is greatest, and palest where 

 it is least". In Europe the same phenomena obtain. Birds 

 from the Scandinavian coast are much darker than in Central 

 Europe, where the rainfall is only half as great. And similarly, 

 British races of birds are darker than the Continental forms. 



Wallace, among others, has contended that light, heat and 

 moisture have no influence on the coloration of animals. 

 Without in this place entering further into the reasons he 

 advances in support of his views, we may remark that the 

 evidence is overwhelmingly against him. That wherever in- 

 dividuals of a widely distributed species settle down and become 

 more or less sedentary, there that species takes on the characters 

 of "local" or "geographical" races, paler or darker, than the 

 parent form, according as they settle in a desert or a marshy 

 area. There is no need here to add to the number of cases 

 which could be cited to show the importance of the action of 

 light and dry heat, and of the effects of a deficiency of sunlight 

 and excess of moisture on coloration. We have chosen the 

 Galapagos to serve as an illustration for other reasons which 

 will be apparent later. 



It is generally believed that the bleached appearance of 

 desert forms is the result of the action of natural selection, 

 whereby all dark coloured, and therefore conspicuous forms, 

 have become weeded out by predatoiy foes, while those indi- 

 viduals which tended towards the development of light plumage 

 survived, in proportion as they harmonised with their surround- 



