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 
