The Laws of Heredity. 151 



find it natural that the law already stated should remain in the 

 purely theoretic state. 



Hence we have to seek in the facts themselves for some empiric 

 formula, which may be deduced from them. Here arise many 

 opinions, of which the following are the chief. 



The simplest is that which holds that there is an invariable 

 connection between the heredity of physical resemblance and the 

 heredity of moral resemblance. That parent who transmits the 

 former, or who influences it most, transmits also the latter, by 

 reason of the strict correlation existing between the two. This 

 doctrine, which has been maintained by Burdach, rests, in principle, 

 on the general relations between the physical and moral natures ; 

 and, in fact, on numerous cases furnished by experience. The case 

 of twins is particularly cited, as commonly presenting an extra- 

 ordinary conformity, not only in the external form and in the 

 features of the face, but also in tastes, in faculties, and even in 

 fortune. 



Da Gama Machado, author of a Theory of Resemblances, 

 which contains a large number of curious facts for the study of 

 physical heredity, holds that the parent who transmits his colour 

 transmits likewise his character. ' In the colonies,' says he, ' the 

 half-breed, called griffon or fusco (dark), resulting from the union 

 of a mulatto and a negress, is much darker than the mulatto. 

 But this difference of colour is accompanied by a difference in 

 character: the issue of a mulatto and a negress are far more 

 docile than the issue of a negress and a white man. If a wild 

 duck couple with a domestic duck, the duckling resulting from this 

 union, having its father's colour, leaves the barn-yard and returns 

 to the wild life. If the linnet be crossed with the canary or the 

 goldfinch, the transmission of instincts will, according to this 

 author, follow the transmission of colour, and if there is a mixture 

 of colours, there will be also a mixture of instincts. 



Girou de Buzareingues, whose experiments on generation are 

 well known, distinguishes two lives in every individual, whatever 

 the sex : The external life, on which depend the nervous system 

 of the animal life and the muscular system, of which motor activity, 

 will, and intelligence are the attributes ; and the internal life, 

 which comprises the cellular tissue, the digestive system, the great 



