REPRODUCTION AND SEX 541 



THEORY OF SEX 



As regards the evolution of sex, we still firmly maintain the 

 general theses of the volume so named in 1889, and of its further 

 developments in Sex (1914). For in these two books, the origins 

 of sex are traced upwards from the general biochemistry of proto- 

 plasmic metabolism; and are based in the appreciable prepon- 

 derance of anabolic processes in the female sex, and of katabolic in 

 the male; which we thence traced through many plant and animal 

 forms, not simply from the large and well-grown ovum and its 

 small and active fertilising element, but also correspondingly in that 

 cell-cycle between passive and active forms which appears to us 

 fundamental to the origin and classification of the Protozoa. In 

 higher and higher forms this sex-process and contrast is increasingly 

 significant; witness, for instance, that rhythmic alternation of 

 generations, in which the asexual generation is so commonly the 

 more vegetative, up to its extreme culmination in the flowering 

 plant. C>r returning to the ordinary succession of generations, we 

 sought, in that elemental conception of sex, the origins of the 

 often striking contrast of the sexes in so many animals which the 

 hypothesis of sexual selection was so long the only endeavour to 

 explain. For the more active katabolism of the male seems the 

 natural source to originate such variations, though, of course, the 

 associated female selection is by no means thereby excluded. In 

 passing, however, it may be noted that while Darwin's essentially 

 psychological hypothesis of female selection is congruent with his 

 later and illustrious development as one of the main founders of 

 evolutionary and comparative psychology, it is in very thorough 

 contrast with his earlier-formed view of variations in general, as in 

 no wise psychic, but simply organic — and "spontaneous and indefi- 

 nite" (at least in the sense of unexplained): whereas a psychologic 

 factor in variation is the essential distinctiveness of Lamarck's 

 doctrine, and not that mere environmental modification, nor assumed 

 use-inheritance, which are so commonly taken as the essential feature. 

 Returning to sex itself, and to our past volumes, with their theses 

 still maintained — and now frequently confirmed, from biochemistry 

 upwards — the fact remains that after more than a whole generation 

 these are still far short of general acceptance. This we take to be 

 primarily explained by the prevalent morphological interest in 

 microscopically working out the particulars of cell-division, and of 

 nuclear structure and behaviour, amazingly intricate and interesting 

 throughout histology generally, and particularly so in the reproduc- 

 tive cells and their observable processes, and here with keen search 

 for light upon the difficult problems of heredity. So far of course 

 well : yet all these structural discoveries do not and cannot exclude 



