VI.] THEIR SIGNIFICANCE IN HEREDITY. 383 



substance, and although it seems to be wasted in the production 

 of enormous quantities of sperm- and egg-cells, such waste is 

 only apparent, and is in reality the means which renders the 

 species capable of existence. It may perhaps be possible to 

 prove that in this case also the waste is only apparent. Such 

 proof would be forthcoming if it could be shown that the means 

 by which reduction is brought about in eggs is advantageous, 

 and therefore also, ceteris paribus^ necessary. We see that 

 everywhere, as far as our observation extends, the useful is 

 also the actual, unless indeed it is impossible of attainment or 

 can only be attained by the aid of processes which are injurious 

 to the species. And if it be asked why germ-plasm is wasted 

 in the maturation of egg-cells, the following may perhaps be a 

 satisfactory answer. 



Let us suppose that the necessary reduction of the germ- 

 plasm does not take place by the separation of the second polar 

 body, but that it happens during the first division of the first 

 primitive-germ-cell which is found in the embryo, so that the 

 first two egg-cells resulting from this division would already 

 contain only half the number of ancestral germ-plasms from the 

 father and the mother, contained in the fertilized egg-cell. In 

 this case the main object, the reduction of the ancestral germ- 

 plasms, would be gained by a single division, and all the 

 succeeding nuclear divisions, causing the multiplication of these 

 first two germ-cells, might take place by the ordinary form of 

 nuclear division, viz. 'equal division.' But perhaps nature not 

 only cares for this one main object alone, but also secures 

 certain secondary advantages at the same time. In the case 

 which we have supposed the egg-cells of the mature ovary 

 would only contain two different combinations of germ-plasm, 

 which we may call combinations A and B. Even if millions of 

 egg-cells were formed, every one of them would contain either 

 A or B^ and hence (at least as far as the female pronucleus is 

 concerned) only two kinds of individuals could arise from such 

 eggs— viz. offspring A' and B'. All the offspring A' would be 

 as similar to one another as identical twins, and the same would 

 be true of offspring B' . 



But if the looth instead of the ist embryonic germ-cell 

 entered upon the ' reducing division,' a hundred cells would 

 undergo this division at the same time, and thus two hundred 



