198 THE EVOLUTION THEORY 



since at every reducing division the ids of the germ-cells are brought 

 down to half their number, a possibility is offered for gradually 

 removing the unfavourable ids from the germ-plasm of the species, 

 since the descendants resulting from the most unfavourable id-combina- 

 tions always perish, and " so from generation to generation the germ- 

 plasm gets rid of its unfavourably varying ids, and the most propitious 

 combinations afforded by amphimixis are preserved, till ultimately 

 there remain only those combinations which are varying appropriately, 

 or at least only those in which the appropriatel}^ varying determinants 

 are in the majority, and so have controlling influence. 



Logicall}^ this deduction is undoubtedly indisputable, from the 

 standpoint of the germ-plasm theorj^ ; but whether it may be regarded 

 as a sufficient reason for the introduction of amphimixis, and for 

 its extremely tenacious persistence throughout the course of the 

 long and intricate phylogeny, cannot be maintained without special 

 investigation. 



Against my position the objection has often been urged that an 

 arrangement cannot arise or be maintained through natural selection 

 unless it is of direct use to the individual in which it occurs. Sexual 

 reproduction cannot therefore have been established simpl}' because 

 it advances, or even because it makes possible the adaptations of 

 species, for these adaptations onl}" came about occasionally, perhaps 

 once in a thousand generations or even less frequently; thus the 

 intervening generations could derive no advantage of any kind from 

 the arrangement in question, and therefore, according to the law of 

 the degeneration of unused characters, it must have long since been lost. 

 I mentioned this objection before, but was obliged to postpone 

 a detailed consideration of it until we had discussed germinal 

 selection. 



We admit, of course, that characters are only preserved intact 

 as long as they are of advantage sufficient to turn the scale in favour 

 of their possessors, and that they begin to fall from their height of 

 perfection when that is no longer the case ; we admit also that new 

 adaptations are not continuall}' necessary, but are so only at intervals 

 of long series of genei-ations, and yet the objection cited seems to me 

 baseless. 



Leaving out of account, for the moment, the first introduction of 

 amphimixis, let us deal with it as an existing occurrence, for the 

 tenacious persistence of which we wish to find reasons. 



Is it really the case that amphimixis is only of importance in 

 connexion with the new adaptation of a species, and that it has nothing 

 to do with the persistence of the species in the state of adaptation 



