PROCEEDINGS 
OF THE 
Cambridge Philosophical Society. 
A possible connexion between abnormal sea-limited transmission 
and sterility. By L. Doncaster, Sc.D., King’s College. 
[Read 17 November 1913.] 
In a recent paper* I suggested that the rare tortoiseshell 
male cat might be produced by the failure of the normal sex- 
limited transmission of the yellow factor from the male parent. 
When a yellow (orange) male cat is mated with a black female, 
the normal result is that all the female offspring are tortoiseshells, 
all the males black, showing that the yellow factor is sex-limited 
in its transmission by the male, and goes only into gametes which 
will give rise to females. Some cases, however, are recorded 
of tortoiseshell males being produced from yellow sires, and I sug- 
gested that these arise by the occasional failure of the sex-limited 
transmission, with the result that the yellow factor is transmitted 
to a male. Such a male, receiving yellow from the male parent 
and black from the female, would be a tortoiseshell. If the black 
factor is also sex-limited in the male, as suggested by Little, 
then a tortoiseshell male could also arise, by failure of the sex- 
limited transmission, from a biack. male by yellow or tortoiseshell 
female, some cases of which have been recorded. It therefore 
seems probable that the rare tortoiseshell male is produced only 
by the abnormal transmission from the sire to a male child of 
a character which normally goes into female producing gametes, 
and that the tortoiseshell male contains two positive factors (those 
for both yellow and black), instead of either one or the other as in 
normal male cats. 
* «On Sex-limited Inheritance in Cats.” Journ, of Genetics, mt, 1913, p. 11. 
+ C. C. Little, Science, May 17, 1912. 
VOL. XVII. PT. IV. 21 
