252 THE STRUGGLE FOR THE LIFE OF OTHERS. 



and female is a later, less fundamental, and, in its 

 beginnings, less essential growth; and long prior to 

 its existence, and largely the condition of it, is the 

 even more beautiful development whose progress we 

 have now to trace. The basis of this new develop- 

 ment is indeed far removed from the mutual relations 

 of sex with sex. For it lies in maleness and female- 

 ness themselves, in their inmost quality and essen- 

 tial nature, in what they lead to and what they be- 

 come. The superstructure, certainly, owes much to 

 the psychical relations of father and mother, husband 

 and wife, but the Evolution of Love began ages before 

 these were established 



What exactly maleness is, and what femaleness, 

 has been one of the problems of the world. At least 

 five hundred theories of their origin are already in the 

 field, but the solution seems to have baffled every 

 approach. Sex has remained almost to the present 

 hour an ultimate mystery of creation, and men seem 

 to know as little what it is as whence it came. But 

 among the last words of modern science there are one 

 or two which spell out a partial clue to both of these 

 mysterious problems. The method by which this has 

 been reached is almost for the first time a purely 

 biological one, and if its inferences are still uncertain, 

 it has at least established some important facts. 



Starting with the function of nutrition as the nearest 

 ally of Reproduction, the newer experimenters have 

 discovered cases in which sex apparently has been de- 

 termined by the quantity and quality of the food-sup- 

 ply. And in actual practice it has been found possible, 

 in the case of certain organisms, to produce either 

 maleness or femaleness by simply varying their nutri- 



