92 MARRIAGE AND HEREDITY 



up to a different trade. Colour-blindness is well 

 known to be hereditary, and to continue through as 

 many as five generations. Similarly, keenness of 

 vision exists among savage tribes to an extent un- 

 known among Europeans, as the result, no doubt, of 

 cultivation and transmission. Smell and taste are 

 also hereditary senses. 



Innumerable illustrations of physical heredity may 

 be found in the works of specialists. Sufiice it to 

 say that the transmission of all congenital charac- 

 teristics, in health or disease, is now an established 

 fact. It is doubted whether accidental peculiarities 

 tend to be transmissible, and Weismann has raised 

 this question in a very crucial form. Circumcision 

 has certainly not been " fixed " among the Jews, nor 

 are smallpox marks hereditary. On the other hand, 

 there are recorded cases of cats and dogs whose tails 

 have been cut off having offspring with short or de- 

 formed tails, though the evidence on this point is not 

 conclusive. 



More remarkable than the heredity of the indi- 

 vidual functions of the body is the alleged transmis- 

 sion of manual dexterity in handicrafts, of what is 

 called an ear for music, of voice and of personal 

 habits depending not upon one organ of the body, 



