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. 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 (Demzegretta) 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. 
100 
