SUMMARY. 23 



no evolution away from sexuality. Long-continued violations of the 

 law of synibasi.s l)rino- onl}' dooeneration. 



This intei[)retation of evolutionary facts opens the wav to an ade- 

 quate physiological explanation of tiie significance of sex, and atiords 

 also a working- theory of the chief cytological complications that have 

 arisen as a consequence of sex — complications that have hitherto 

 rendered obscure the nature of the cell-bodies of higher animals and 

 plants. 



The external diversity of organic nature and the internal diversity 

 of cells and of reproductive processes take on new and unexpected 

 significance. Both are shown to be consequences of sexual specializa- 

 tion, without which no evolutionary advance beyond simple-cell colo- 

 nies has been possible, ^lore .than this, gradations in the perfections 

 of the higher double-celled structure are correlated with definite stao-es 

 of evolutionary progress, so that from the structure of an org'anism 

 its kind of sexuality can be deduced. Evolution becomes, in the new 

 view, a physiological rather than a morphological process, since the 

 methods of descent afiect the quality and efficiency of the organism 

 even more promptly and fundamentally than they do its external 

 form. 



