1908.] INHERITANCE OF COLOUR IN PIGEONS. 99 



changed to white or orange usually within two months after 

 hatching. In the foregoing experiments no matings were made 

 specially to test the inheritance of the colour of the iris, and this 

 character has only been studied incidentally. From lack of space 

 it was found necessary to kill many of the young birds before the 

 coloui' of the iris in the adult state could be noted ; and in the 

 earliest experiments no notes were taken of the minor characters 

 presented. 



Some few cases were met with in which the colour of the iris 

 did not completely change, but a small segment of one iris re- 

 mained permanently black, or the greater part of both irides was 

 black and only a small part showed white or orange. One bird 

 was bred having one iris black and the other orange, but this 

 appeared to be a very exceptional case. 



The Barb pigeon has generally a white eye, although black 

 Barbs are sometimes seen with orange eyes. White Barbs have 

 been seen with white eyes, but nearly always have black. Of the 

 four black Barbs used, those in Exps. 2, 27, and 34 had white 

 irides. That used in Exj). 1 is believed to have had an orange 

 iris, the notes of this experiment referring to plumage colour only. 

 The white Fantails had black irides ; coloured Fantails, on the 

 other hand, have either white or orange. The black and white 

 Nun had white irides. The white Tumbler also had white irides ; 

 this character has been specially referred to in the description of 

 the Tumbler. 



In the four series of experiments irides were obtained as 

 follows : — 



Barb-Fantail Cross gave white, orange, and black. 



Barb-Nun Cross gave white only. 



Barb-Fantail-Nun Cross gave white, orange, and black. 



Fantail-Tumbler Cross gave black only. 



There appears to be a very distinct association between white 

 plumage and black iris, and, in a lesser degree, between black 

 plumage and white iris, as the following tables show (p. 100). 

 Here the birds are grouped ii-respective of the generations to 

 which they belong. 



In the case of the blue birds with some white feathers there 

 appeared to be a general, though not invariable, rule that the 

 birds showing the greatest amount of white had black irides and 

 those with fewer white feathers orange irides. 



The tables show very conclusively the relation between the 

 white plumage and black irides. This correlation extends to the 

 whites with some coloured feathers, and even to the mottled birds 

 in which white is in excess. It is further seen that no black bird 

 has a black iris, and the black iris is also exceptional in black 

 birds with some white feathers. In the Barb-Fantail cross there 

 appears to be a correlation between the white iris and black 

 plumage ; the figures, however, of the Barb-Fantail -Nun cross, 

 although small, do not bear this out. 



7* 



