Nature of Sexual Diversity 115 



tween the sexes? In a general way the male in most organ- 

 isms is the more active and the less inclined to store up re- 

 serve food in its tissues; the female less active and given 

 to storing up more reserve nutrition. These differences are 

 of course seen most clearly in the germ cells of the two 

 sexes; the typical male germ cells are minute and actively 

 motile, while the female germ cells (eggs) are large and 

 inert, with much food material stored in them. Less marked 



Figure 31. Differences between the chromosomes of the nuclei in 

 the two sexes. A and B, male and female chromosome groups, re- 

 spectively, of the hemipterous insect Protenor, after Wilson (1910). 

 The nucleus of the female (B) has two of the large chromosomes x, 

 while the male (A) has but one. 



C and D, male and female chromosome groups respectively, in the 

 nuclei of the fruit fly Drosophila, after Morgan (1916). The male" 

 group (C) has one bent chromosome (Y) in place of one of the straight 

 ones (X) of the female (D). 



differences of the same general character distinguish the 

 male and female individuals that produce these germ cells. 



Many attempts have been made to express such differences 

 in general terms. Geddes and Thompson (1880) say that in 

 the female the preponderating process is that of anabolism, 



