226 Heredity, 



tlio hen alone was protuberant. Blurnenbaeh, who par- 

 ticularly attended to abnormal peculiarities in domestic 

 animals, states, in 1813, that this was the case; and Bech- 

 stein had previously, in 1793, observed the same fact. 

 This latter author .... expressly states that he never 

 observed this protuberance in male fowls. Hence there 

 can be no doubt that this remarkable cliaracter in the 

 skulls of Polish fowls was formerly in Germanv confined 

 to the female sex, but has now been transferred to the 

 males, and has thus become common to both sexes." 



These few cases are clearly exceptional, and the study 

 of domesticated animals shows us that, as a rule, the 

 males of allied breeds, like the males of wild species, 

 are more different from each other than the females. 

 AVe cannot attribute this difference to sexual selection, 

 for most of our domesticated animals, especially those 

 of pure blood, are prevented by man from following 

 their own inclination in the selection of mates. Neither 

 can we assert that man has devoted especial attention to 

 the selection and modification of males, and has aimed 

 at changes in those organs which are most developed in 

 males, for, among pigeons at least, the opposite of this 

 is the case, and a female bird of equal excellence is more 

 Yalued than a male. We are thus forced to conclude 

 not only that ^^ among domesticated animals the male is 

 more variable than the female" (Darwin, Sexual Selec- 

 tion, Vol. I. p. 266), but also that organs which are con- 

 fined to males, or unusually developed in them, are more 

 apt than organs which are confined to females, to trans- 

 mit their variations, and thus to give rise to hereditary 

 race modifications. As our domesticated races show, by 

 their close similarity to natural species, that the causes 

 which have produced them are very similar to those 

 which have acted upon wild organisms, we are justified 



