L. DONCASTER 379 



This scheme is exactly comparable with T. H. Morgan's results on 

 the inheritance of the white eye in Drosophila ', in which no suggestion 

 of alternative dominance has ever been made ; if N represents the 

 factor for red eye and n its absence (white eye), the scheme does as 

 well for Drosophila as for human colour-blindness. 



The scheme here outlined will apply to all cases of a character 

 apparently dominant in one sex only and also sex-limited in its 

 transmission by that sex (with the possible exception of the orange 

 colour in cats, the inheritance of which is not adequately known). 

 It will not apply to cases which show no sex-limitation in inherit- 

 ance (e.g. horns of sheep) ; in these it must probably be supposed 

 that a sex -limited modifying factor is present in one sex. 



1 Morgan, Science, 32. 1910, p. 120 ; American Naturalist, 45. 1911, p. 65. 



CAMBRIDGE : PKIXTED BY JOHN CLAY, M.A. AT THK tJNIVEESITY PRESS 



