450 Evolution and Adaptation 
Thus we reach the somewhat startling conclusion that 
through natural selection the germ-cells and their protozoan 
prototypes have been rendered incapable, through natural 
selection, of reproducing by non-sexual methods, in order 
that variations may be supplied for the farther action of 
this same process of natural selection. The speculation has 
the appearance of arguing in a circle, although if it were 
worth the attempt an ingenious mind might perhaps succeed 
in showing that such a thing is not logically inconceivable. 
It seems strange that a claim of this sort should have been 
made, when it is so apparent that the most immediate effect 
of intercrossing is to swamp all variations that depart from 
the average. Even if it were true that new combinations of 
characters would arise through the union of the germ-cells of 
two different animals, it is certainly true that in the case of fluc- 
tuating variations this new combination would be lost by later 
crossing with average individuals. Moreover, it is well known 
that variations occur amongst forms that are produced asex- 
ually. On the whole, it does not seem to be a satisfactory 
solution of the problem to assume that sexual reproduction 
has been acquired in order to supply natural selection with 
material on which it may work. 
Our examination of the suggestions that have been made 
and of the speculation indulged in, as to what benefit the 
process of sexual reproduction confers on the animals and 
plants that make use of this method of propagation, has failed 
to show convincingly that any advantage to the individual or 
to the species is the outcome. This may mean, either that 
there is no advantage, or that we have as yet failed to 
understand the meaning of the phenomenon. The only light 
that has been thrown on the question is that a certain amount 
of renewed vigor is a consequence of this process, but we 
cannot explain how this takes place. There is also the sug- 
gestion that the union of different cells produces the same 
beneficial effect as a change in the conditions of life produces 
