Experiments with other Mammals 115 



zygous. It is also evident why orange females are very rare, 

 although orange males are common, since in all matings in 

 which one of the parents is black, orange can appear only in the 

 male offspring. "If, therefore, the great majority of orange 

 males contain recessive black, when they are paired with tor- 

 toiseshells, only a quarter of the kittens will be pure orange, and 

 only half of these females." 



The preceding statements show the relation of the colors orange 

 and black. The inheritance of two other colors was also ex- 

 amined ; namely, cream and blue. Cream appears to be a dilute 

 form of orange, and blue of black. The blues breed true (when 

 derived from yellow ancestors) and are therefore recessives or 

 homozygous. A cream female and a blue male give blue tor- 

 toiseshell (blue and cream), cream males, but no blues, since 

 the cream dominates incompletely in the female, completely in 

 the males. On the other hand, a blue female and a cream male 

 give blue tortoiseshell females, blues of both sexes, and possibly 

 cream males. These and other results show that the dilute 

 forms behave in the same way as do the stronger colors. Thus 

 cream is dominant over blue in the male, but when blue and 

 cream meet in the female a tortoiseshell results. 



It has been stated that male tortoiseshell cats are known, 

 although they are rare. It must be assumed that in such cases 

 the dominance of the yellow is incomplete as in the female. This 

 means that while complete dominance is usually associated 

 with the male character, it is not necessarily always associated 

 with this sex. It is interesting to find that when a male tor- 

 toiseshell is mated with a female of the same color, the kittens 

 are tortoiseshell, orange, and black. This is what is expected 

 on the assumption that the germ-cells of the tortoiseshell are 

 black and orange (with the alternate character latent on my view). 

 The prepotency of different tortoiseshell individuals (males) 

 seems, however, to vary. 



It should also be pointed out that the colors described above 

 may be associated with a certain amount of white which reap- 

 pears in the offspring without, however, affecting the inheritance 



