INHERITANCE OF HUMAN CHARACTERS 461 
matings by =. The circles are of solid color @ in individuals affected 
with the deformity, open O in normal individuals. The character 
seems to behave like a Mendelian dominant, though one could make 
no very positive assertion on this point from so few individuals. But 
it is very evident that such a physical character once in the stock is 
transmitted generation after generation, reappearing continually in 
the offspring. 
Below there is presented a chart (Fig. 97) of the transmission 
of cataract. This disease is characterized by the appearance of 
an opaque area in the usually transparent parts of the eye, 
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Fic. 97.—Inheritance of one form of cataract. Modified from Nettleship’s 
chart. The diagram reads thus: A man with cataract married a normal woman; 
of their eight children six were affected with the disease. One of these married 
an unaffected man; three of the children of this union were normal, sex unrecorded, 
two defective. This same man married a second wife who was normal; their 
eight children were all unaffected. So continue reading through five generations. 
(From Downing.) 
ultimately rendering the person blind. In the particular form 
of the disease here considered it does not develop until middle 
life. Clarence Loeb in a study of hereditary blindness published 
in 1909 tabulated the results of a study of 304 families in which 
such blindness occurs. There were 1,012 children, of whom 58 per 
cent were afflicted, which is about the percentage expected when 
hybrid defectives mate with normal individuals and the defect is a 
dominant character. Similar extensive studies of congenital deafness 
and deaf-mutism show that these are similarly heritable, though just 
how the character behaves is not yet known, for undoubtedly under 
“deafness” are included a variety of diseased conditions that must be 
