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THE AMERICAN NATURALIST [Vol. L 



cataracta punctata, formed by minute white dots scattered uni- 

 formly through the lens or grouped in the anterior cortical 

 layers, and other forms of circumscribed, stationary, lenticular 

 opacities which though rare are known to be congenital (3) , have 

 also been used in the compilations given here. 



Senile cataract, which also seems to be hereditary, and those 

 forms of cataract arising from lesions, diseases of the eyeball, and 

 certain general diseases such as cholera and tetany, have been 

 omitted. 



Although congenital and other forms of cataract have long 

 been considered by the medical profession to be influenced by 

 heredity, no definite analysis was made until 1905, when the first 

 paper by Nettleship (1) appeared. Nettleship's data have been 

 the basis of Bateson 's (9) conclusion that the abnormality is in- 

 herited as a dominant character. Bateson acknowledges that 

 normal parents have produced abnormal children, but these 

 cases he explains as either origin de novo, or due to faulty clas- 

 sification of the parents, who in reality may have been slightly 

 affected with cataract. 



Davenport (3) has followed Bateson 's conclusion in regard 

 to the inheritance of cataract, and makes the eugenic recommen- 

 dation that unaffected parents from affected stock may marry 

 without fear (if producing abnormal children. 



In the "Treasury of Human Inheritance" Harman (2) gives 

 one hundred genealogical tables dealing with congenital cat- 

 aract. Each table represents two or more generations with a 

 detailed account of the condition of each individual in regard to 

 congenital defects of the eye. The data used in this paper have 



which there is no doubt as to the condition of the parents or 

 the children in respect to the abnormality, and where there is 



three different categories, ^as follows: (A) both parents normal 



least one abnormal child; (C) both parents abnormal, giving 



There are 31 families with both parents normal which give 

 some abnormal children. In a total of 153 children from these 



