SEXUAL SELECTION. 225 



become lighter-colored during the winter; and I have myself ob- 

 served, and heard of similar strongly marked changes of color, 

 that is, from brownish 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 sea- 

 sons 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 inheritance, at 

 least with those animals which do not present strongly-marked 

 sexual differences, and indeed with many of these. But characters 

 are somewhat commonly transferred 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 instances 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, acquired 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 trans- 

 mitted to the same sex alone. So general is this form of transmis- 

 sion 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, whilst 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.™ The wattle in the 

 English Carrier pigeon, and the crop in the Pouter, are more 

 highly developed in the male than in the female; and although 

 these characters have been gained through long-continued selec- 

 tion by man, the slight differences between the sexes are wholly 

 due to the form of inheritance which has prevailed; for they have 

 arisen, not from, but rather in opposition to, the wish of the 

 breeder. 



Most of our domestic races have been formed by the accumula- 

 tion of many slight variations; and as some of the successive steps 

 have been transmitted to one sex alone, and some to both sexes, we 

 find in the different breeds of the same species all gradations be- 



5= Dr. Chapuis, 'Le Pigeon Voyageur Beige,' 1865, p. 87. Boitard et 

 Corbie, 'Les Pigeons de Voliere,' &c., 1824, p. 173. See, also, on sim- 

 ilar differences in certain breeds at Modena, 'Le variazioni dei Col- 

 ombi domestioi,' del Paolo Bonizzi, 1873. 

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