THE EVOLUTION OF SEX 21 



the ways between plants and animals; the 

 differentiation of Protozoa and Protophyta 

 from one another and among themselves; 

 the establishment of multicellular bodies ; the 

 beginnings of brains and of behaviour; the 

 evolution of the dominant types of the animal 

 kingdom; and, finally, the emergence and 

 ascent of Man the supreme Mammal. We 

 have now to inquire into the evolution of 

 sex and the significance of the various steps 

 so far as these can be read at present. 



ANCIENT ORIGIN OF SEX. The cords of 

 human love are complex, even in its average 

 expressions in civilised mankind. There is 

 a subtle interweaving of strands physical 

 and psychical, aesthetic and intellectual, 

 individual and social. Yet in spite of all 

 transfiguration, the flesh and blood attraction 

 persists, and we land in fallacy if we forget 

 that these sex-impulses which are at once 

 the glory and the shame of mankind and 

 this increasingly throughout the ages have 

 a yet inconceivably longer history behind 

 them, and thence spring up within us with 

 the tremendous momentum of the organic 

 past. 



It is a significant fact that we are confronted 

 with sex at the very roots of the genealogical 

 tree in the primeval sub-kingdom of the Uni- 

 cellulars, the Protozoa and the Protophytes. 

 In these relatively simple organisms multi- 

 plication takes place by fission or by budding, 

 or by spore-formation ; but along with these 

 modes of multiplication there is a quite 

 distinct process, that combination of two 

 individuals which is called conjugation. It 



