2/8 EVOLUTION OF TO-DAY. 



be exactly like its parents and grandparents. Thus 

 far the theory is similar to that of Weismann, al- 

 though Brooks arrived at the hypothesis indepen-r 

 dently. To continue with Brooks. Since, therefore, 

 the ovum is confined to the female sex, an animal 

 inherits from its mother the characteristics of the 

 race which have been long continued, and which its 

 mother inherited from remote generations. If repro- 

 duction were confined to the female sex, there would 

 be no chance for the inheritance of acquired features. 

 (Exceptions to this rule will appear presently.) 

 Congenital variations might appear, but this would 

 be all. Brooks has collected a large amount of evi- 

 dence, which he thinks proves this point. He finds 

 that in animals where parthenogenesis occurs, /. e., 

 reproduction through the female sex alone, there is 

 almost no variation, all individuals being almost 

 exactly alike for generation after generation. He 

 thinks, therefore, that were reproduction confined 

 to the female sex, variations would be comparatively 

 rare. 



But reproduction is not confined to the female 

 sex, and variation is, according to Brooks, due 

 chiefly to the influence of the male. To explain 

 this, he supplements his theory with a modification 

 of Darwin's pangenesis. Like Darwin, he assumes 

 that the various parts of the body are capable of 

 giving off from themselves little bodies called gem- 

 ules. But, instead of imagining them to be scat- 

 tered indefinitely through the body, he assumes that 

 it is the especial function of the male element to 

 collect them. The gemmules arising from the various 



