42 MAMMARY APPARATUS OP THE MAMMALIA 



have been made to surmount this difficulty. 

 The best known of these assumes that origin- 

 ally only the female possessed the mammary 

 apparatus, and then transferred it to the male 

 by " amphigonous inheritance." The case has 

 been greatly simplified through the possibility, 

 formerly lacking, of referring to the brooding 

 organs of loM'^er forms. It is by no means 

 necessary to assume that the original brooding 

 organs of the pre-mammalian ancestors existed 

 only in the female ; they can (^uite well have 

 been common to both sexes from the besrin- 

 ning, as is the case with many birds, where 

 male and female share in the business of 

 broodins:. 



With the presence of these brooding organs, 

 a disposition to the development of the 

 mammary apparatus was given to the male 

 as well, especially if, as is not impossible, 

 he took part in brooding during the earliest 

 stages of mammalian history. The mammary 

 apparatus then was not exclusivelv acquired 

 by the female, but arose quite naturally in 

 both sexes alike, on the ground of inherited 

 disposition, and not until the disappearance 

 of its function in the male did it underg-o 



