The Making of Species 



after death into this type of eye that is, with 

 the pupil black and the iris blue. It is to be 

 observed that this kind of eye sometimes occurs 

 in coloured horses, rabbits, and dogs. Finally, 

 we have white mutations in which the eye loses 

 none of the pigment. These are abundant in 

 nature, and probably most of the white species 

 of birds as, for example, some egrets, swans, 

 etc. arose in this way. 1 Pure white species are 

 comparatively uncommon in nature, because, 

 except in snow-clad regions, white creatures are 

 easily seen by their adversaries. Most white 

 birds are of considerable size, and well able to 

 look after themselves. 



Similarly black mutations occur frequently 

 among animals, both under domestication and 

 in a state of nature. All are familiar with black 

 dogs, cats, horses, fowls, ducks, pigeons. Black 

 mutations, however, do not occur nearly so 

 frequently as white ones. So far as we are 

 aware no black mutation has been recorded 

 among canaries, geese, guinea-fowl, ferrets, 

 Java sparrows or doves, all of which produce 

 white mutations. 



On the other hand, in the wild state black 

 species occur more frequently than normal-eyed 

 white forms. This is probably because such 



1 Some egrets, such as the rock-egrets (Demiegrettd) of eastern 

 tropical coasts, are normally grey, but may be white, and this 

 whiteness may be confined in individuals to the young or adult 

 States. 



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