THE SEXES AND SEXUAL SELECTION. n 



supposing that the male is more exposed than the female to the 

 action of selection, whether natural or sexual. Darwin concludes, 

 indeed, that the male is more variable than the female, but he gives no 

 satisfactory reason why female variations should be less apt than male 

 variations to become hereditary, or, in other words, why the right of 

 entail is so much restricted to the male sex. Darwin merely attributes 

 this to the greater eagerness of the males, which, "in almost all 

 animals, have stronger passions than the females." The theory 

 which Brooks maintains is bound up with an hypothesis of heredity 

 differing considerably from that held by Darwin. He supposes that 

 the cells of the body give off gemmules, chiefly during change of 

 function or of environment, and that ' ' the male reproductive cell has 

 gradually acquired, as its especial and distinctive function, a peculiar 

 power to gather and store up these gemmules." The female 

 reproductive cells keep up the general constancy of the species, the 

 male cells transmit variations. ' ' A division of physiological labor has 

 arisen during the evolution of life, and the functions of the reproductive 

 elements have become specialized in different directions." "The 

 male cell became adapted for storing up gemmules ' ' (the results of 

 variations in the body), "and at the same time gradually lost its 

 unnecessary and useless power to transmit hereditary characteristics." 

 " We thus look to the cells of the male body for the origin of most of 

 the variations through which the species has attained to its present 

 organization." The males are the more variable, but, more than that, 

 their variations are much more likely to be transmitted. "We are 

 thus able to understand the great difference in the males of allied 

 species, the difference between the adult male and the female or young, 

 and the great diversity and variability of secondary male characters; 

 and we should expect to find, what actually is the case, that among 

 the higher animals, when the sexes have long been separated, the 

 males are more variable than the females." The contrast between 

 Darwin and Brooks may now be summed up again in a sentence. 

 Darwin says the males are more diversified and richer in secondary 

 sexual characters, chiefly because of the sexual selection exercised 

 alike in courtship and in battle. Brooks admits sexual selection, but 

 finds an explanation of the greater diversity of the males in his theory 

 that it is the peculiar function of the male elements to transmit 

 variations, as opposed to the constant tradition of structure kept up by 

 the egg-cells or ova. In other words, the females may choose, yet the 

 males lead; nay more, they must lead, for male variations have by 

 hypothesis most likelihood of being transmitted. 



Full consideration of this hypothesis would involve much 

 discussion of the problems of inheritance, which will form the subject 



