290 Colour Inheritance in Cats 



(2) The unexpected but normally pigmented individuals appearing 

 in certain matings (Headings 1, 2, and 3, Section ii) can be accounted 

 for by supposing that F becomes 3/ in a certain proportion of the gametes 

 of exceptional individuals. 



(3) Sterile tortoise-shell males may possibly be " near males " formed 

 as a result of non-disjunction of the X chromosome and therefore YBX— 

 in constitution. 



(4) Fertile tortoise-shell males may also be the product of non- 

 disjunction (secondary) and would be zygotes formed from the fusion of 

 gametes YBX6 and -. These males in gametogenesis would behave as 

 ordinary yellows. 



LITERATURE CITED. 



Bridges, C. B. 1913. " Non-Disjunction of the Sex Chromosomes of Drosophila." 

 Journ. Exp. Zool. Vol. xv. p. 587. 



1916. (a) " Non-Disjunction as Proof of the Chromosome Theory of Here- 

 dity." Genetics, Vol. i. p. 1. 



1916. {h) " Non-Disjunction as Proof of the Chromosome Theory of Here- 

 dity." Genetics, Vol. i. p. 107. 



Cutler, W. D., and Doncaster, L. 1915. " On the Sterility of the Tortoise-Shell 



Tom Cat." Journ. of Genetics, Vol. v. p. 65. 

 Doncaster, L. 1904. " On the Inheritance of Tortoise-shell dnd Related Colours 



in Cats." Proc. Camb. Phil. Soc. Vol. xiii. p. 35. 



1912. "Sex- Limited Inheritance in Cats." Sci N. S. Vol. xxxvi. p. 144. 



1913. " On Sex-Limited Inheritance in Cats, and its Bearing on the Sex- 

 Limited Transmission of Certain Human Abnormalities." Journ. of Genetics^ 

 Vol. ni. p. 11. 



1914, " A Possible Connexion between Abnormal Sex- Limited Transmission 



and Sterility." Proc. Camb. Phil. Soc. Vol. xvii. p. 307. 



Hyde, R. R. 1916. "Mosaics in Drosophila Ampelophila.'' Genetics, Vol. i. 



p. 581. 

 Ibsen, H. L. 1916. " Tricolor Inheritance. III. Tortoise-shell Cats."' Genetics, 



Vol. I. p. 377. 

 Little, C. C. 1912. " A PreUminary Note on the Occurrence of a Sex- Limited 



Character in Cats." Sd. N. S. Vol. xxxv. p. 784. 



1916. "The Occurrence of Three Recognized Color Mutations in Mice." 



Amer. Nat. Vol. l. p. 335. 



Whiting, P. W. 1915. " The Tortoise-Shell Cat." Amer. Nat. Vol. xlix. p. 518. 

 1918. " Inheritance of Coat Colour in Cats." Journ. Exp. Zool. Vol. xxv. 



p. 539. 

 Wright, S. 1918. "Colour Inheritance in Mammals. X. The Cat." Journ. 



Heredity, Vol. ix. p. 139. 



