HEREDITARY TRAITS. 215 



from the pure hexadactylic type, there can be no doubt that 

 under favourable conditions the colony would have become 

 a nation of six-fingered folk. Among such a nation the 

 duodecimal system of notation would flourish, and some 

 remarkable performers on the pianoforte, flute, and other 

 instruments, might be looked for ; but we do not know that 

 they would possess any other advantage over their penta- 

 dactylic contemporaries. Seeing that the system of colonis- 

 ing above described is antecedently unlikely, and that no 

 special advantage could be derived from the persistence of 

 any hitherto known abnormal variety of the human race, it 

 is unlikely that for many generations yet to come we shall 

 hear of six-fingered, hairy-faced, horny- skinned, or hare- 

 lipped nations. The only peculiarities which have any 

 chance of becoming permanent are such as, while not very 

 uncommon, stand in the way of intermarriage with persons 

 not similarly affected. A similar remark, as will presently 

 appear, applies to mental and moral characteristics. The 

 law according to which contrast is found attractive and 

 similitude repugnant, though wide in its range, is not uni- 

 versal ; and there are cases in which resemblance, if it has 

 not the charm found (under ordinary circumstances) in con- 

 trast, is yet a necessary element in matrimonial alliances. 



The inheritance of constitutional traits comes next to 

 be considered. It is probably not less frequently observed, 

 and is in several respects more interesting than the inherit- 

 ance of peculiarities of bodily configuration. 



Longevity, which may be regarded as measuring the 

 aggregate constitutional energy, is well known to be heredi- 

 tary in certain families, as is short duration of life in other 

 families. The best proof that this is the case is found in 

 the action of insurance companies, in ascertaining through 

 their agents the longevity of the ancestors of persons pro- 

 posing to insure their lives. Instances of longevity during 

 several successive generations are too common to be worth 

 citing. Cases in which, for generation after generation, a 

 certain age, far short of the threescore years and ten, has 



