0. J. Bond 113 



experiments in pigeons during the last seven years which are of interest 

 in this connection'. 



It is well known that whiteness of plumage is associated in pigeons 

 with a dark brown iris or "bull" eye. Bull eye is an expression used 

 by fanciers to denote a dark brown eye which looks black at a distance 

 and in which it is difficult to see the outline of the pupil without close 

 examination. If however the bull eye be examined at an angle with 

 a lens, an outer zone of pinkish red colouration can be observed near 

 the periphery of the iris which at first suggests red pigment in this 

 situation. After removal of the eye however and the emptying of 

 the blood vessels the pink colour largely disappears and microscopical 

 sections of the iris show that the pink appearance is due not to the 

 deposition of pigment but to exposed blood vessels on the anterior 

 surface of the iris. Thus the bull eye is a simplex eye in which the 

 posterior uveal pigment is seen through the delicate iris tissue. 



A homozygous white fantail cock with "bull" eyes was mated to 

 a black fish-tailed short billed tumbler hen with pink eyes-. 



The F^ offspring of this cross were black and white, and brown 

 (with blue) and white hybrids, all with dominant orange red or duplex 

 iris. 



Two of these, a black and white cock and a brown blue and white 

 hen (brother and sister) were mated together and produced in the F^ 

 generation : ; 



Of these F„ heterozygotes a black and white cock with orange red 

 eyes was mated to a brown, blue and white hen, with orange red eyes, 

 producing in the i^s generation : 



Of these the black and white, brown and white, almonds, and 

 almonds and whites, have the dominant red eye, the white the recessive 



' Heterochromia in pigeons is apparently according to fanciers more common in 

 Tumblers and chiefly in the Pied varieties, it also occurs in Homers. 



^ It should be stated that in the pigeon experiments the pairs, when once mated, were 

 not confined, but were allowed to mingle with other birds in the same loft. If care be 

 taken to keep all the adult birds properly mated, I have not found any difficulty arise from 

 non-isolation. 



