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 



