I20 Pile Fowls [CH. 



by Miss Durham agree entirely with those of Cuenot She 

 finds it impossible to obtain any mice pure to yellow. The 

 experience of fanciers seems to be universal that yellows 

 cannot be bred in a pure strain. Those with which she 

 has experimented always throw either agoutis, blacks, or 

 chocolates, and we may take it that yellows of both sexes 

 are always heterozygotes formed by the meeting of a 

 yellow and a non-yellow gamete*. In spite of their genetic 

 composition the yellows which throw chocolates have only 

 yellow pigment in their hairs, and no chocolate. 



Cats. 



In cats we meet a new complication in the inheritance 

 of yellow, namely that it is disturbed by sexual dimorphism. 

 The rarity of tortoise-shell males is well known, and Don- 

 caster (109) has produced evidence which makes it prac- 

 tically certain that in the immense majority of instances 

 the female heterozygote of orange x black is tortoise-shell, 

 namely, patched with orange and black (like the guinea-pig), 

 but that the male heterozygote similarly produced is orange 

 (see Chap, x, dealing with the heredity of Sex). The 

 dilute types cream and blue are similarly related to blue 

 tortoise-shell. 



Fowls. 



There are further indications of peculiarity in the genetics 

 of yellow pigments in the case of birds. The coloration 

 known as " Pile " in fowls is seldom bred for exhibition 

 from two pile birds. The colour consists, in cocks, of 

 orange-yellow or red in the hackles and wing-coverts com- 

 bined with a white ground. The hens are white, with a 

 chestnut or reddish yellow breast. In the down the chickens 

 of both sexes have longitudinal stripes of light chestnut. 

 In the adults, and generally in the chickens too, there 

 is a small and variable amount of blackish grey ticking, 

 which is of course considered a fault. Pile is a colour 

 known in several breeds, but especially in Game, Game 



* Besides this curious peculiarity, yellows show another remarkable 

 feature in their frequent tendency to become excessively fat. Miss Durham 

 has met with several such specimens and the fact is well known to fanciers. 

 In her experience also yellows are more liable to sterility than other mice. 



