548 P. W. WHITING 
(M.Y) and one cream (24) (A’.b.m.Y); and two females—one 
black (a.M.yy) and one orange and black (a.M.Yy). 
When crossed with (41, 46, and 50) her cream son (24) 
(A’.b.m.Y) she produced in three litters three males—one 
blotched maltese (A.b.m.y), one maltese (a.b.m.y), and one cream 
(m.Y); and two cream females (m. YY). 
When crossed with (38) an orange-striped male (B.M.Y), she 
produced one black male (a.M.y) and three females—two striped 
orange (B.M.YY) and one striped orange and black (a.B.M.Yy). 
Summarizing the matings of this cream and white female, we 
find that when bred to ‘black’ males (yX —) she produced two 
‘black’ males (yX —), two ‘yellow’ males (YX —), two tortoise- 
shell’ females (YX yX), and one black female (yX yX). 
When bred to ‘yellow’ males (YX —), she produced three 
‘black’ males (yX —), one ‘yellow’ male (YX —), four ‘yellow’ 
females (YX YX), and one tortoiseshell female (YX yX). 
Of these matings Dr. Little says: ‘‘The dilute yellow and white 
female is interesting because she forms gametes carrying black and 
breeds exactly like a dilute tortotseshell and white animal, although 
there is no trace of black pigment anywhere on her.”’ She is 
then an anomalous yellow. Dr. Little further states: ‘‘ Dilute 
yellow, like the same color in mice, does not depend upon the 
depth of color, but is essentially a dull yellow ranging anywhere 
from intense pigmentation to dilute cream color.” It is of 
course relatively not as intense as the orange. It is possible that 
this variation in cream color is due to the same factors which 
produce the variations towards silver in tabbies and others. 
Yellow-spotting in cats may be compared essentially to the 
same condition in guinea-pigs. In the latter there is great 
range of variability asin the former. In cats, however, one of the 
allelomorphie pairs determining black or yellow extension is 
much more potent than the others and is sex-linked. The het- 
erozygous female (YX yX) represents a much more unstable 
condition as regards spotting than either of the homozygous 
females or than either of the haploid males, for in the heterozy- 
gote the factors yellow, Y, and black, y, are balanced against 
each other. 
