LXX BOWMAN LECTURE. 



incipient senile cataract would have been found in some, 

 perhaps a fair number, of those who, judging only from 

 report, have been entered as normal ; the 40 per cent, 

 is therefore too low, though we cannot say by how much. 



II. Congenital cataract of all kinds. Descent contin- 

 uous : total 566 (100), affected 260 (46), normal 306 (54), 

 a bad approximation to the equality required by the 

 Mendelian scheme, Fig. 6 E, if the pedigrees used are 

 as complete as they are supposed to be. 



III. Retinitis pigmentosa; pedigrees showing contin- 

 uous descent only: total 387 (100), affected 198 (51), 

 normal 189 (49). Practical equality as in Fig. 6 E. 



IV. Congenital night - blindness with continuous 

 descent. For quantitative purposes the great Cunier 

 pedigree is too inexact for this purpose. Other data 

 give : total 63, affected 33, normal 30. Not far from 

 equality, as required by Fig. 6 E. 



V. Leber's disease. Descent discontinuous, all cases, 

 female as well as male, being counted: total 547 (100), 

 affected 245 (45), normal 302 (55). A poor approach to 

 equality. 



It must, however, be mentioned that in this disease the 

 proportion of diseased to normal is influenced by sex. 



(a) In families where the disease affects males exclu- 

 sively the numbers are total, both sexes, 402 (100), 

 affected males only, 165 (41), normal, both sexes, 237 (59). 



(h) In families where the disease affects some females 

 as well as males the numbers are totals, both sexes, 145 

 (100), affected, both sexes, 80 (55), normal, both sexes, 

 65 (45). 



VI. Retinitis pigmentosa; pedigrees showing invariably 

 discontinuous descent. 



The numbers in this group can be interpreted in 

 Mendelian terms on the assumption that the disease is 

 dominant in some sibships and generations, recessive in* 

 others. 



The totals are small, but may, for the present, be 

 analysed into three sub-groups as follows : 



