1 94 Heredity. 



CHAPTER IV. 



EXCEPTIONS TO THE LAW OF HEREDITY. 



THE study of the laws of heredity would not be complete with- 

 out an examination of the exceptions. Nothing gives a clearer 

 notion of the nature of a law, than a knowledge of its anomalies. 



Here, especially, this is indispensable, for the infractions of 

 hereditary transmission are so numerous and so striking, that from 

 time to time we ask with hesitation if the law exists at all beneath 

 the phenomena which conceal it On considering these difficulties, 

 we shall understand why the author of the most famous work 

 upon this subject should have set up over against heredity an 

 equal and contrary law, that of innateness, which as he considers 

 explains all the exceptions. 



Before discussing this hypothesis, and showing how heredity 

 may explain the exceptions no less than the regular cases, we will, 

 as usual, begin by a statement of facts. 



In the physiological world, these exceptions are readily shown 

 in the internal or external structure, the physiognomy, the stature, 

 constitution or temperament 



Though, generally, brothers and sisters have a family likeness, it 

 is not rare that there is between them such a diversity of feature 

 and countenance that no external sign would indicate their com- 

 mon blood. This difference is sometimes seen even in twins. 

 Sinibaldi asks * how it comes that at Rome ugly boors and women 

 from the dregs of the people, with hideous features, produce sons 

 and daughters of surprising beauty, and of such perfect form that 

 their equals are not to be found in the palaces of nobles, or in the 

 courts of princes.' 1 



Fathers and mothers of erect form, none of whose families have 

 ever been misshapen, produce children hunchbacked and de- 

 formed. Deformed parents have bad perfectly straight children. 

 Parents of middle height sometimes beget tall children, while other 



1 Might not this be a fact of atavism ? 



