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coloured birds having the best constitutions would be strongest 

 and most successful in all the struggles of existence. They would 

 therefore, leave most descendants, and, these characteristics be- 

 coming intensified in each generation, the origin and development 

 of brilliancy of colouring is naturally explained. 



Mr. Grant Allen, on the other hand, while fully admitting 

 the force of Mr. Wallace's main argument as to colour resulting 

 from excess of vital power, maintains that this view fails to 

 explain the development of one hue in preference to another. 

 Mr. Allen, therefore, invokes the agency of sexual selection 

 influenced by a love of bright hues, and introduces an entirely 

 fresh factor to account for their origin. Associating the colours 

 of birds with their food, he argues that most of the gorgeously 

 coloured species feed on bright-hued insects, flowers, or fruit, 

 while the dusky forms are nourished by dingy food-stuffs such as 

 murky insects, seeds, or carrion. From the evidence in favour of 

 this theory, most clearly and exhaustively stated in his fascinating 

 volume on " The Colour Sense," he infers that the avian taste for, 

 and perception of, colour has not only effected tha diff ision and 

 coloration of fruits, but, strengthened by pleasurable exercise, 

 has also re-acted on the birds themselves, in developing an 

 appreciative love of bright hues, and, thus influencing their 

 choice of mates, has resulted in the perpetuation and gradual 

 intensification of brilliancy of plumage. 



In considering the evidence relating to the theory of the 

 reptilian origin of the avian races, it is especially necessary to 

 make due allowance for the influence of such important factors 

 as the imperfection of the geological record, tendencies to vary, 

 the effect of surrounding circumstances in retarding or developing 

 those tendencies, and the survival of the fittest in the struggle for 

 existence. 



Many imperfections in the geological records of the avian 

 class have been explained by the assumption that birds gifted 

 with the power of flight would be less liable to be destroyed by 

 sudden floods than other animals, an argument which is 

 strengthened by the fact of the comparative abundance of 

 fossilised wingless forms, as compared with the greater scarcity of 

 those of the flying birds. It has also been suggested that their 

 remains would float longer on the surface of the water, and so be 

 more liable to be devoured. That numerous kinds of birds 

 existed in the later Secondary epoch may be justifiably inferred 

 from the marked and divergent characters of the few preserved 

 to us. Others, possibly entombed in unsuitable deposits, were 



