PRACTICAL LAWS OF LIFE 345 



Since these people are a burden to themselves and to 

 society, no right-minded person could risk the responsibility 

 for bringing them into the world ; and as the facts come to 

 be generally known, all such streams of bad blood will be 

 prevented from increasing their kind and also from spread- 

 ing out to contaminate streams of normal blood. 



Color of eyes and hair, night blindness, color blindness, 

 albinism, germinal deaf-mutism, and many other human 

 characters have been found to follow Mendel's law, but dis- 

 covery is only beginning to break into this field, and we 

 merely suggest it for future individual study. Most impor- 

 tant studies have been made on typical streams of bad 

 heredity. Let different members of the class volunteer to 

 look up the following and report : tf The Jukes Family," by 

 Dugdale ; " The Zero Family," by Jorger ; " The Hill Folk," 

 by Danielson and Davenport ; ' The Nam Family," by 

 Estabrook and Davenport ; and " The Kallikak Family," 

 by Goddard. 



