22 Sex-Limited Inheritance in Cats 



tortoiseshell male should on this hypothesis be Yx . BX, and since B is 

 coupled with X, such a male should transmit B to his daughters and Y 

 to his sons. Mated to black he should have black female and tortoise- 

 shell male offspring ; mated to a tortoiseshell he should have tortoiseshell 

 and black daughters, yellow and tortoiseshell sons. Of the mating of a 

 tortoiseshell male with a black I have only one somewhat doubtful 

 record, but hope to be able to test the matter with a tortoiseshell male 

 now in my possession ; in the several matings with tortoiseshell females 

 which are reported, no tortoiseshell males were produced — the tortoise- 

 shell male behaved as far as can be judged from the very incomplete 

 reports as if he were a yellow. 



Other possible schemes miglrt be suggested, for example that yellow 

 is due to an additional factor modifying B and usually coupled with it, 

 but occasionally becoming dissociated so that the yellow male would 

 transmit B to a female kitten and the modifying factor to a son. The 

 tortoiseshell male so produced, however, would still receive the modifying 

 factor from the male parent and B from the female, and it would be 

 expected, if these factors followed the ordinary rules of gametic coupling, 

 that they would show repulsion in the gametogenesis of the tortoise- 

 shell male, so that again the modifying factor would be transmitted to 

 the male offspring and tortoiseshell males would be produced as in the 

 previous scheme. 



It seems clear, therefore, that the data at present available are 

 inadequate for the formulation of a factorial scheme of colour-inheritance 

 in Cats, which shall be in accord with previously known cases of sex- 

 limited inheritance and of gametic coupling in other forms. For any 

 one, however, who is able to undertake the work, the experiments 

 required are fairly clear, and the importance of the case is increased by 

 the fact that the transmission of the yellow colour in the Cat is in close 

 agreement, both in its normal course and in the exceptions which occur, 

 with the transmission in Man of the sex-limited affections Colour- 

 blindness, Night-blindness, Nystagmus and Haemophilia. Although 

 so much has been written about the transmission of these diseases, no 

 agreement has been reached, and it seems probable that the inheritance 

 of colour in the Cat, with which definite experiments can be made, and 

 in which the " transmitting female " can be distinguished at sight from 

 the " non-transmitting," may provide the clue which the most complete 

 human pedigrees would fail to yield. 



In conclusion, I wish to tender my thanks to the following ladies 

 and gentlemen who have provided the information given in the 



