1 62 Heredity. 



without value ; they might say that their thesis is only a special 

 application of a maxim generally admitted with regard to gener- 

 ation, viz. that like produces like. When we treat of reversional 

 heredity, we shall endeavour to show that the conflict between 

 these two opinions is only apparent, and also how they may be 

 harmonized. 



Among the physiological facts which exhibit heredity trans- 

 mitted in the same sex, we may cite the family of Edward 

 Lambert, the human porcupine, in which a peculiar affection was 

 transmitted only to the males. Daltonism, or colour-blindness, 

 manifests itself more frequently, as we have seen, in men than in 

 women ; yet it has been transmitted through five generations to 

 twelve persons, all females. Constitution, temperament, fecundity, 

 longevity, idiosyncrasies, or anomalies of every kind, pass as often 

 from father to son as from mother to daughter. 



From the psychological point of view, as we have said, Bail- 

 larger, resting on the statistical data of mental disease, inclines to 

 the belief that heredity usually occurs between individuals of the 

 same sex. His 671 cases were distributed as follows : 



CASES OF MENTAL DISEASE. 



Total. 



In the father 225 In the mother 346 571 

 sons 128 daughters 197 325 



daughters 97 sons 149 246 



We now turn to the statistical reports made to the French 

 Government in 1860, of which we have already spoken. 



MEN WOMEN 



In 1,000 cases. In 1,000 cases. 



128 inherited from the father 130 inherited from the mother 



no the mother TOO the father 

 26 both. 26 both. 



It is plain that these two tables lead to the same conclusions. 



We hold that the study of mental disease is of great importance 

 for experimental psychology, and well adapted for resolving many 

 problems ; yet we would not place over-much confidence in it in 

 the present case. 



