20 PRINCIPLES OF STOCK-BREEDING. 



former have the defect. In the eighth there was 

 no issue, and in the ninth there are two sisters, 

 both of them capable of appreciating colors. Of 

 the fifth generation, the defective perception has 

 hitherto been detected in but two of the families. 

 In one of them, consisting of three brothers and 

 three sisters, one of the brothers has the defect, 

 and in the other, a male, an only child, is similarly 

 affected." * 



The peculiar condition of the lens of the eye ob- 

 served in short-sighted people is hereditary, as is also 

 the opposite defect, giving what is known as long 

 sight. 8 



" Day-blindness, or imperfect vision under a bright 

 light, is inherited, as is night-blindness, or an inca- 

 pacity to see except under a strong light. A case has 

 been recorded by M. Currier of this latter defect 

 having affected eighty-five members of the same fam- 

 ily during six generations." a 



Dr. Earle likewise gives the case of a family in 

 which a defective musical ear is associated with an 

 imperfect appreciation of colors. 



In a family of my acquaintance a peculiarity in 

 the walk is hereditary. 



Kibot says that in some families the hair turns 

 gray in early youth, and similar cases have come under 

 my own observation. 



The loss of the teeth, when a particular age is 



1 American Journal of the Medical Sciences, vol. xxxv., p. 347 ; 

 quoted in " Cyclopaedia of Anatomy and Physiology," vol. iv., p. 1453. 

 9 Darwin, " Animals and Plants under Domestication," vol. ii., p. 17. 

 3 Darwin, loc. cit., vol. ii., pp. 19, 269. 



