Heredity and the Law of Evolution. 293 



issue of a union in the third degree of consanguinity. In the 

 course of one hundred and sixty years there were ninety-one 

 marriages in that family, sixteen of them consanguineous, and 

 yet there resulted neither infirmity nor sterility. Similar facts are 

 cited by MM. Voisin and Dalby. There are two small French 

 islands, Batz and Brehat, in which consanguineous marriages are 

 very frequent, yet the population is healthy and vigorous. 



The two opinions may, perhaps, as M. de Quatrefages observes, 

 be reconciled. The tendency of heredity is to reproduce the 

 whole being ; the child is only a resultant, a compromise between 

 the tendencies of both the parents. If these tendencies are the 

 same, they are all the more evident in the product. If the parents 

 enjoy perfect health, consanguinity will tend to preserve it in their ^ 

 descendants, and then, so far from being prejudicial, it will have 

 good results. But that perfect equilibrium which constitutes 

 physical and moral health may easily be disturbed in the parents, 

 and then the consequences will become more and more evident in 

 the children. Now, in consanguineous marriages the chances are 

 many that this disturbance of equilibrium will be of a like nature 

 in both of the parents. Hence it follows that in many cases such 

 unions will be injurious, and all the more dangerous in proportion 

 as the morbid predispositions common to both parties are more 

 marked. ' The consequence we are to draw from all these facts 

 would appear to be, that near relationship between father and 

 mother is not in itself hurtful, but that, in virtue of the laws govern- 

 ing heredity, it oftentimes becomes so ; and hence, in view of the 

 eventualities to which consanguinity leads, it is at least prudent to 

 avoid consanguineous marriage.' x 



It would therefore appear that the ' in and in ' method adopted 

 for the improvement of the lower races would have little likelihood 

 of success if applied to man, and that we must renounce this plan 

 of fixing and of making organic certain intellectual aptitudes. The 

 process of crossing families would probably be better. This would 

 consist in selecting a pair out of two different families, both pos- 

 sessed in a high degree of the particular quality, talent or tendency, 

 which it is desired to transmit to the progeny in increased propor- 



1 Quatrefages, Rapport sur les Progres de T Anthropology, p. 461. 



