Chap. XVIII.] EQUAL TRANSMISSION 283 



their ornamental appendages, and in tlieir colors. In both 

 classes, when the male differs from the female, the young 

 of both sexes almost always resemble each othei*, and in a 

 large majority of cases resemble the adult female. In both 

 classes the male assumes the characters proper to his sex 

 shortly before the age for reproduction; if emasculated 

 he either never acquires such characters or subsequently 

 loses them. In both classes the change of color is some- 

 times seasonal, and the tints of the naked parts sometimes 

 become more vivid during the act of courtship. In both 

 classes the male is almost always more vividly or sti'ongly 

 colored than the female, and is ornamented with larger 

 crests either of hair or feathers, or other appendages. In 

 a few exceptional cases the female in both classes is more 

 highly ornamented than the male. With many mammals, 

 and at least in the case of one bird, the male is more odor- 

 iferous than the female. In both classes the voice of the 

 male is more powerful than that of the female. Consider- 

 ing this parallelism there can be little doubt that the same 

 cause, whatever it may be, has acted on mammals and 

 birds ; and the result, as far as ornamental characters are 

 concerned, may safely be attributed, as it appears to me, 

 to the long-continued preference of the individuals of one 

 sex for certain individuals of the opposite sex, combined 

 with their success in leaving a larger number of offspring 

 to inherit their superior attractions. 



Equal Transmission of Ornamental Characters to both 

 Sexes. — With many birds, ornaments, which analogy leads 

 us to believe were primarily acquired by the males, have 

 been transmitted equally, or almost equally, to both sexes ; 

 and we may now inquire how far this view may be ex- 

 tended to mammals. With a considerable number of spe- 

 cies, especially the smaller kinds, both sexes have been 

 colored, independently of sexual selection, for the sake of 



