86 EVOLUTION OF THE HUMAN EYE 



upon fruits, while none of them are very specially connected 

 with flowers. Hence a large set of possible tests which 

 we can employ in the case of insects and birds are wholly 

 inapplicable to mammals. Moreover, the want of close 

 relations with the colored parts of plants lias probably 

 resulted in a want of any peculiar love for bright color, 

 such as we see reason to suspect in the butterflies, humming- 

 birds and parrots. This absence of taste for brilliancy is 

 probably marked by the absence of brilliant hues in the 

 animals themselves; the result of sexual selection for these 

 hues, as we shall see hereafter, only appears among the 

 Mammalia in a few higher arboreal and frugivorous species 

 such as the mandril and certain squirrels." 



Alfred Russell Wallace, 45 in discussing the origin of the 

 color-sense, said: "The primary necessity which led to the 

 development of the sense of color was probably the need of 

 distinguishing objects much alike in form and size but 

 differing in important properties, such as ripe and unripe 

 or eatable and poisonous fruits, flowers with honey or with- 

 out, the sexes of the same or of closely allied species. In 

 most cases the strongest contrast would be the most useful, 

 especially as the colors of the objects to be distinguished 

 would form but minute spots or points when compared 

 with the broad masses of tint of sky, earth or foliage against 

 which they would be set." 



The association of brilliant hues in the external coverings 

 of animals with those of the objects from which they obtain 

 their food is very striking. Humming-birds, which are 

 the most highly colored of all birds, obtain their food from 

 flowers; they have a bifid tubular tongue which they insert 

 into the corolla of flowers to suck up the honey. Parrots, 

 whose plumage is generally extremely bright and gaudy, 

 live for the most part on brightly colored fruits. The 



