INHERITANCE OF COAT-COLOR IN CATS 549 
The sterility of the tortoiseshell tom has frequently been re- 
marked upon. Cutler and Doncaster (’15) discuss this question 
and show drawings of sections of the testis of a sterile cat of this 
sort. Normal reproductive cells are altogether lacking. In 
summarizing the data on sterility of male tortoiseshells, they 
find that one was certainly fertile, two completely sterile, one 
almost if not quite sterile, and two doubtful. It appears, then, 
that sterility may be highly correlated with yellow-spotting in 
the male. 
The black-yellow allelomorphic pair in cats is of particular 
interest, as it is the only case of sex-linkage known in mam- 
mals, other than the sex-linked defects of man. 
D. Siamese dilution 
Bateson (713) says of the Siamese cats: ‘‘These animals, which 
breed perfectly true, were introduced from Siam, where they 
have been kept for an indefinite period as pets of the royal 
household. Like the Himalayan rabbit, Siamese cats are born 
almost white, but the fur becomes a curious fawn with darker 
chocolate points on the ears and extremities.’’ Crosses of Sia- 
mese by other cats are cited by Weir (’89). Quoting from a Mr. 
Young, he says (p. 76), ‘‘They invariably showed the Siamese 
cross in the ground color.” But Lady Dorothy Nevill says, 
‘““None showed any trace of the Siamese, being all tabby.” 
Two pregnant females of common cats brought into the lab- 
oratory produced kittens of a peculiar ashy color with darker 
extremities. The kittens resembled very closely adult Siamese 
cats. 
One of the pregnant females; a maltese (5) (a.m.) produced 
(15) two females which were ashy, with nose, ears, feet, and tail 
slightly darker, and two females and two males which were ashy 
with black extremities. A record taken fifty days after birth 
showed that the lighter kittens had become maltese, while the 
kittens with black extremities had become steel colored or almost 
black. They later became completely black. Ghost patterns 
were seen on four of the kittens, but unfortunately a critical 
