130 HEREDITARY CHARACTERS 



Considering the matter in its general aspect, we are 

 obliged to fall in with the suggestion conveyed by the 

 distribution of the chromosomes in fertilisation. Under 

 natural conditions, that is, where there is no artificial in- 

 tervention with regard to the selection of the parents, the 

 most numerous offspring will tend to be produced by the 

 best generally equipped males and the most attractive and 

 best-equipped females. The result, therefore, will be the 

 tendency to perpetuate in the race those characters pos- 

 sessed by individuals varying in these directions. Besides 

 the variations in these directions, variations in other direc- 

 tions will certainly occur. Some of these variations will 

 be advantageous to the individuals possessing them. They 

 will be transmitted to the offspring in a greater or less 

 degree. Those which inherit the advantageous character 

 with a variation towards an increase, will have an advantage 

 over those offspring which inherit with a variation in the 

 opposite direction, and a still greater advantage over other 

 individuals in the race which do not possess the character 

 at all. Thus natural selection will perpetuate the advan- 

 tageous characters, and will increase each of them according 

 to the stringency of the selection. Some other variations 

 will not be advantageous, and therefore will not be subject 

 to selection, but will tend to be eliminated in a compara- 

 tively short time. It is improbable that a variation which 

 is not the subject of natural selection will be present in 

 both parents. It is still less likely that such a variation 

 will be present, both in the offspring of these parents, and 

 in the individuals with which these offspring pair in their 

 turn. Thus, all characters not the subject of selection must 

 tend to be eliminated by bi-parental reproduction through 

 a process of swamping. Bi-parental reproduction, in fact, 

 tends to eliminate individual variations whatever they may 

 be ; while natural selection tends to preserve such individual 

 variations as give their possessors an advantage over their 

 fellows. In a sense, bi-parental reproduction and natural 

 selection are working against each other, bi-parental repro- 



