126 Evolution and Adaptation 



more and more increased would be continually favoured or 

 selected, until at last a complete separation of the sexes 

 might be effected. It would take up too much space to 

 show the various steps, through dimorphism and other 

 means, by which the separation of the sexes in plants of 

 various kinds is apparently now in progress ; but I may add 

 that some of the species of holly in North America are, 

 according to Asa Gray, in an exactly intermediate con- 

 dition, or, as he expresses it, are more or less diceciously 

 polygamous." 



From this it will be seen that Darwin supposes that the 

 separation of the sexes in some of the higher plants has been 

 brought about by natural selection. Despite the supposed 

 advantage of the so-called "division of labor," one may, I 

 venture to suggest, be sceptical as to whether the separation 

 of the sexes can be explained in this way. The whole case is 

 largely supposititious, since in most of the higher hermaphro- 

 ditic plants and in nearly all hermaphroditic animals the 

 sexual products ripen at different times in the same indi- 

 vidual. Hence there is no basis for the assumption that 

 unless the sexes are separated there will be self-fertilization. 

 Shall we assume that this difference in time of ripening 

 of the two kinds of sex-cells is also the outcome of natural 

 selection, and that there has existed an earlier stage in all 

 animals and plants, that now have different times for the 

 ripening of their sexual elements, a time when these products 

 ripened simultaneously ? I doubt if even a Darwinian would 

 give such loose rein to his fancy. 



But this is not yet the whole story that Darwin has made 

 out in this connection, for he continues : — 



" Let us now turn to the nectar-feeding insects ; we may 

 suppose the plant, of which we have been slowly increasing 

 the nectar by continued selection, to be a common plant ; and 

 that certain insects depended in main part on its nectar for 

 food. I could give many facts showing how anxious bees 



