80 BIOLOGY AND SOCIAL PROBLEMS 



ably by the same means as in animals like 

 Protenor, in that when the human &gg is 

 fertilized by a sperm with twenty-three chro- 

 mosomes a male results and when by a sperm 

 with twenty-four chromosomes a female is the 

 outcome. If, as in insects, the two kinds of 

 spermatozoa in man are about equally numer- 

 ous, we can understand why male and female 

 human births are so nearly equal in number. 



From what has been stated concerning the 

 composition of the fertilized egg and the na- 

 ture of sex determination, it must be clear 

 that the chromosomes are most significant 

 bodies in inheritance, in fact they seem to be 

 the vehicles of this process. The reason we 

 inherit from our two parents those character- 

 istics of feature and action which mark us as 

 their descendants is because they have each 

 contributed a certain number of chromosomes 

 to our make-up. 



Simple as this statement is, when we face 

 the full actualities of the case, it strains even 

 the imagination. That so small an amount of 

 material as that represented in the chromo- 

 somes of the fertilized egg should influence in 

 so rigid a way so large an amount as that con- 

 tained in the adult body seems almost incredi- 



