vi] Eye-Colours 113 



there are suggestions that it is not the whole, and that 

 further complications have to be met. To discuss these in 

 detail is beyond the scope of this work, but it seems likely 

 that the degree of saturation or dilution of the coat-colour 

 has to be considered. 



There is evidently some intimate relation between the 

 colour of the eye and the colour of the coat ; for no mice 

 have the coat-colour wild-grey ("agouti" of fanciers), 

 black, or even blue, unless the eyes are black. The 

 interesting fact has also been discovered that the actual 

 nature of the pigment of the choroid differs in the different 

 varieties*. Miss Durham finds that the chocolate mice 

 always have chocolate eyes, not black, no black pigment 

 being present in either iris or choroid. The same fact has 

 been published by Castle (53) for the guinea-pig and was 

 also noticed independently by Miss Sollas in guinea-pigs. 

 From these observations it is to be inferred that either the 

 coat-colour controls the eye-colour, or the colour of the eye 

 controls that of the coat, but for various reasons it is not 

 possible yet to declare positively which account is the right 

 one. 



Guinea-pigs differ from other animals in that their 

 albino strains generally have small "smudges" of blackish 

 pigment on some of the extremities, especially the tips of 

 the ears, though the eyes are entirely without pigment. It 

 is said that albino guinea-pigs occur without these smudges, 

 but I have not seen one. 



The Cinnamon Canary must also be noticed here. 

 This variety on hatching has pink eyes, though as develop- 

 ment proceeds, pigmentation supervenes. Many fanciers 

 believe that they can recognize a difference between the 

 eyes of Cinnamons and those of other varieties, but the 

 distinction is not readily obvious. In plumage Cinnamons 

 differ from other breeds in that the black pigment is 

 absent and the feathers consequently have a brownish tint. 

 Miss Durham, from her observations, concludes that the 

 pigment which is developed in both eyes and feathers is 

 chocolate, and that the Cinnamon is in fact a chocolate 



* John Hunter has an important paper on this subject : " On the 

 Colour of the Pigmentum of the Eye in different Animals" (Obs. on 

 certain Parts of the Animal Economy, 1786, p. 199). 



B. H. 8 



