SEXUAL SELECTION 303 



of similar strongly marked changes of color, that is, from 

 trownish cream-color or reddish-brown to a perfect white, 

 in several ponies in England. Although I do not know 

 that this tendency to change the color of the coat during 

 different seasons is transmitted, yet it probably is so, as 

 all shades of color are strongly inherited by the horse. 

 Nor is this form of inheritance, as limited by the seasons, 

 more remarkable than its limitation by age or sex. 



Inheritance as Limited by Sex. — The equal transmission 

 of characters to both sexes is the commonest form of inheri- 

 tance, at least with those animals which do not present 

 strongly marked sexual differences, and indeed with many 

 of these. But characters are somewhat commonly trans- 

 ferred exclusively to that sex in which they first appear. 

 Ample evidence on this head has been advanced in my 

 work on ""Variation under Domestication," but a few in- 

 stances may here be given. There are breeds of the sheep 

 and goat in which the horns of the male differ greatly in 

 shape from those of the female; and these differences, ac- 

 quired under domestication, are regularly transmitted to the 

 same sex. As a rule, it is the females alone in cats which 

 are tortoise-shell, the corresponding color in the males being 

 rusty-red. With most breeds of the fowl, the characters 

 proper to each sex are transmitted to the same sex alone. 

 So general is this form of transmission that it is an anomaly 

 when variations in certain breeds are transmitted equally to 

 both sexes. There are also certain sub -breeds of the fowl 

 in which the males can hardly be distinguished from one 

 another, while the females differ considerably in color. The 

 sexes of the pigeon in the parent- species do not differ in 

 any external character; nevertheless, in certain domesticated 

 breeds the male is colored differently from the female." 



'» Dr. Chapuis, "Le Pigeon Yoyageur Beige," 1865, p. 87. Boitard et 

 Oorbi^, "Les Pigeons de Voliere," etc., 1824, p. 173. See, also, on similar 

 differences in certain breeds at Modena, "Le variazioni dei Colombi domestici," 

 del Paolo Bonizzi, 1873. 



