MENDELISM AND SEX 193 



They furnish examples of the disasters which tend to befall us 

 when we limit the area whence we draw the materials for thought, 

 and fail to test our thinking in every way possible, when, in fact, 

 our attitude is sectarian, not scientific. 



318. The question of the relation between sexual and 

 Mendelian characters cannot, however, be disposed of in this 

 summary fashion. At any rate, since the reader may still consider 

 it a matter of opinion whether the inheritance of sexual characters 

 is Mendelian or the reproduction of Mendelian characters sexual, 

 it ought not to be so disposed of. It is necessary to make the 

 usual deductive inference of consequences, and then to compare 

 these consequences with reality. It is an indisputable truth that 

 living beings exist and have undergone evolution. Does the 

 hypothesis that the inheritance of characters, including the sexual, 

 is Mendelian accord with this truth, or is it incompatible with it? 

 Or, on the contrary, does the hypothesis that inheritance tends 

 to be blended, and that Mendelian traits are abnormalities of 

 sexual reproduction introduced by man, accord with it? In 

 brief, we have now to investigate the function of conjugation, 

 of sex. 



319. If the Mendelian theory is true, the effect and, therefore, 

 presumably, the function of conjugation is to mix parental 

 characters as marbles are mixed, not to blend them as colours 

 are blended. Now suppose, for example, that a tall man mates 

 with a short woman and offspring are born to them. This means 

 that both parents have been so well adapted to the environment, 

 and their characters so well co-adapted to one another, that they 

 have been enabled to survive till they were mature. But if 

 characters are transmitted independently of one another, the ' tall ' 

 and ' short ' characters of the parents will be mixed in the 

 offspring. This is not what happens in nature. It is not even 

 what happens when artificial varieties are crossed by man ; for 

 only a very few of the characters (e.g. colour of plumage and extra 

 toe) of such varieties have been established by him through the 

 selection of mutations. But it is what is implied in the Mendelian 

 doctrine. It must be remembered that tallness and shortness in 

 human beings and other animals depend, not on a single character 

 like internodal length in the pea, but on a multitude of structures, 

 all of which are supposed to be inherited independently of one 

 another. 1 Moreover, relative tallness and shortness are not neces- 

 sarily fluctuations, for there are stable tall and short human races 



1 Bateson, Mendel's Principles of Heredity, p. 209. 



