88 



MAN, — THE ANIMAL 



States, "It has been estimated that in the period 

 of thirty years, between the twenty-fifth and fifty- 

 fifth year of manhood, one individual will pro- 

 duce the prodigious number of 339,385,500,000 

 spermatozoa !" 



It is immaterial whether these estimates for the 



Figure 29. The human egg cell, the ovum, surrounded by 

 several layers of special cells. Compare this cell with the one 

 shown in Figures 4 and 16. The cytoplasm of this egg is not 

 supplied with much nutrient material and the forming embryo 

 must be nourished by the parent, 



number of ova and sperms are correct or not; the 

 essential fact is that a very large number of both 

 are produced. The proportion that actually de- 

 velops and shares in producing new human beings 

 is so small that it constitutes a decided exception. 

 The mere production of this vast number of living 

 germ cells is the source of a number of our human 

 problems of reproduction. 



