38 Mr Doncaster, On the Inheritance of Colours in Gats. 



Several smaller points remain which are not quite clear. 

 On the hypothesis that in the male orange is dominant over black 

 and cream over blue, while in the female these combinations give 

 tortoiseshells, yellow males should result from the pairing black % 

 x orange </" (or blue % x cream <£ ). I have obtained no certain 

 evidence that this occurs ; my correspondents mention black 

 (or blue) and tortoiseshell, but say nothing of yellows, but in one 

 mating of this kind a male tortoiseshell was produced. 



Male tortoiseshells are occasionally obtained, and it must be 

 supposed that in them the dominance of the orange is incomplete. 

 A tortoiseshell J 1 paired with a female of the same colour gives 

 tortoiseshell, orange, and black kittens. I hear however of one 

 case where a tortoiseshell mated with his own daughters of the 

 same colour produced almost entirely orange or orange-and-white 

 kittens, and a small proportion of blacks; with other tortoiseshell 

 females my correspondent says "he sired tortoiseshells freely." 



All the colours mentioned may be associated with a certain 

 amount of white, and this reappears in the offspring without 

 affecting the inheritance of other colours ; the presence of white 

 (i.e. the piebald character) seems to be a separate allelomorph as 

 in the case of rats and mice. 



My investigation of the inheritance of tortoiseshell colour was 

 undertaken in connexion with a general inquiry into the nature 

 of varieties confined to one sex, but does not appear to be 

 analogous to other cases known to me. 



Varieties confined to one sex appear to be of several kinds ; they 

 may be Mendelian recessives, as in the variety lacticolor of Abraxas 

 grossulariata, exhibited this year at the British Association, and 

 in this case by suitable mating the variety may be transferred to 

 the male. Human colour-blindness is possibly also of this nature, 

 but is usually found in the male instead of the female. A second 

 type is when a local race resembles the normal form in one sex, 

 but differs in the other, e.g. % var. bryoniae in Pieris napi, or 

 ^ var. rustica in Spilosoma mendica. In such cases a cross 

 between the two races yields intermediates, and reciprocal crosses 

 give similar results. Finally in the tortoiseshell cat the female 

 variety seems to be produced by defective dominance in one sex 

 of a colour completely dominant in the other. 



In conclusion I wish to acknowledge my indebtedness to my 

 numerous correspondents, especially Miss W. Beal, and Sir C. 

 Alexander, for the large amount of information received from 

 them, only a small part of which I have been able to include in 

 the account given. 



