100 



MR, R. STAPLES-BROWNE ON 



[Feb. 18, 



The doubtful record of the iris of the Barb used in Exp. 1, 

 and the absence of notes on the irides in some of the earHer 

 expeiinients, makes the tracing of inheritance of this character 

 very unsatisfactory. 



Barb-Fantail Cross. 



A very clear result is, however, obtained in Exp. 2, which was 

 made later. In this case a Barb with a white iris was mated to 

 a Fantail with a black iris, and the fovir young produced had 

 white irides. Two of these mated together in Exp. 4 gave 

 13 birds with white irides, and 4 with black. Three other young 

 were produced, but were killed before the colour of the iris could 

 be ascertained. This, therefore, gives the simple 3 : 1 Mendelian 

 proportion in F. 2, w^hite being dominant. 



The remaining crosses, both of the Barb-Fantail and the Barb- 

 Fantail-Nun experiments were, unfortunately, all made with birds 

 descended from the Barb used in Exp. 1. 



The results of these expei-iments are grouped together in the 

 following tables irrespective of the generations to which the birds 

 belonged. 



