58 THE WAY LIFE BEGINS 



The special set of organs in the two sexes set apart to carry 

 out the work of reproduction were originally the same, since 

 they correspond part for part. In all of the higher forms, 

 the sex cells show this division into sperm and egg cells, but 

 there are animals in which the two kinds of reproductive 

 apparatus are found in one body. The same is true of plants. 

 Indeed, if we go back far enough in the plant and animal world 

 the difference between sperms and eggs disappears, and there 

 is left but the union of two similar cells as the first step in 

 producing another life. 



