COURTSHIP OF BIRDS 137 



one of the lines of interpretation. There is much to be said 

 for the view that there is a deep constitutional difference 

 between the male and the female organism an initial or 

 germinal difference in the balance of chemical changes. The 

 female seems to be relatively more constructive, relatively 

 less disruptive. There is a fundamental difference in what 

 we call figuratively the protoplasmic rhythm the physi- 

 ological gearing. This initial difference leads to the 

 primary functional distinction between male and female. 

 But it also determines, either from the start, or after 

 maleness and femaleness have been in part established, 

 what particular expression will be given to a whole series 

 of minor characters both structural and functional 

 whether a masculine or a feminine expression. It is 

 convenient to keep the terms maleness and femaleness 

 for the primary functional distinction the male salmon 

 depositing the fertilising milt upon the eggs which are 

 liberated from the roe or ovary of the female salmon ; 

 and to keep the terms masculine and feminine for the 

 contrasted expression that analogous characters find in 

 the two sexes. 



We cannot here do more than indicate the nature of 

 the evidence in support of the view that a deep, initial, 

 constitutional difference expresses itself primarily in what 

 we call maleness or femaleness, and is also decisive, late 

 or early, directly or indirectly, in determining whether 

 detailed characters will find a masculine or a feminine 

 expression. One egg becomes a cock, another egg a hen ; 

 but no microscopic differences are detectable ; and no 

 one yet knows what gives the egg a bias towards 

 maleness or femaleness. In the higher animals at least 

 the divergence is initial, and in a short time it finds 

 visible expression. The developing creature gets on to 

 definitely male or female lines, and the getting on to 



