178 Sex-limited Inheritance [CH. 



evidently replacing the black pigment characteristic of 

 " green " canaries. The green is of course due to the black 

 pigment showing through the yellow. According to Miss 

 Durham's observations the cinnamon pigment is of the 

 same nature as the "chocolate," of which we have spoken 

 in discussing the pigmentation of mammals, and it is 

 probable that the various aberrational forms of mammals 

 and birds so often recorded by systematists as " isabelline " 

 are all similar cases of the replacement of black by 

 chocolate. 



When newly hatched, Cinnamons differ very strikingly 

 from ordinary canaries in the fact that they have pink or 

 unpigmented eyes, like the albinos of many animals. As 

 they grow up this distinction is scarcely, if at all, per- 

 ceptible on ordinary examination. The eyes become pig- 

 mented and come to look about as dark as those of ordinary 

 canaries. Some fanciers allege that they can distinguish 

 the eyes of Cinnamons throughout life, but the difference is 

 evasive and these determinations are unreliable. Micro- 

 scopically, however, Miss Durham finds that there is a real 

 difference in the fact that the pigment of the Cinnamon eye 

 is chocolate, like that of the chocolate mouse. Apparently 

 the cinnamon feathers are never developed in birds that 

 have black eyes, but the pink eyes can be transferred to 

 birds which are pure yellow and without any trace of 

 cinnamon in their feathers. 



The inheritance with which we are concerned is that of 

 the pink eyes. It has long been declared by fanciers that 

 when Cinnamon hens, viz. pink-eyed, are bred with green, 

 viz. black-eyed, cocks the offspring of both sexes all come 

 black-eyed. When however green (black-eyed) hens are 

 bred to Cinnamon (pink-eyed) cocks, both greens and 

 Cinnamons may be bred, but these Cinnamons are 

 always hens. The F^ black-eyed cocks are said to have 

 again the power of producing pink-eyed offspring from 

 black-eyed hens, but again all these pink-eyed birds are 

 hens. Statements to this effect are to be found in many of 

 the fanciers' books, but a particularly good and lucid account 

 of the phenomena was given by Mr Noorduijn (213), of 

 Groningen, who has been good enough to answer many 

 questions on the subject. 



