THE STRUGGLE FOR THE LIFE OF OTHERS 315 



that we accept the sex separation as a matter of 

 course ; but no words can do justice to the wonder 

 and novelty of this strange line of cleavage which 

 cuts down to the very root of being in everything 

 that lives. 



No theme of equal importance has received less 

 attention than this from evolutionary philosophy. 

 The single problems which sex suggests have been 

 investigated with a keenness and brilliance of 

 treatment never before brought to bear in this 

 mysterious region ; and Mr, Darwin's theory of 

 sexual selection, whether true or false, has called 

 attention to a multitude of things in living Nature 

 which seem to find a possible explanation here. 

 But the broad and simple fact that this division 

 into maleness and femaleness should run between 

 almost every two of every plant and every animal 

 in existence, must have implications of a quite ex- 

 ceptional kind. 



How deep, from the very dawn of life, this 

 rent between the two sexes yawns is only now 

 beginning to be seen. Examine one of the hum- 

 blest water weeds — the Spirogyra. It consists of 

 waving threads or necklaces of cells, each plant 

 to the eye the exact duplicate of the other. Yet 

 externally alike as they seem, the one has the 

 physiological value of the male, the other of 



