448 



THE AMERICAN NATURALIST 



[Vol. L 



In chart 342, 111-28 and 111-37 are shown as a pair of parents 

 both of whom are affected in both eyes. The descriptions quoted 

 from Nettleship by Harman (op. cit., p. 148) show that the diag- 

 nosis is evidently based on ophthalmoscopic examinations. This 

 is a clear case of abnormal by abnormal, and if we were to regard 

 it as " doubtful" we could find equal justification for so regard- 

 ing any other chart in the whole series. The offspring of this 

 marriage are seven children, of whom two have cataract, three 

 thought to have been free from it died in infancy, and two are 

 , definitely known to be normal. This is the one critical case that 

 is needed and, taken at its face value, it completely refutes the 

 argument for the recessive nature of congenital cataract. 



In conclusion, the writer does not wish to insist on arguments 

 from a few particular cases, nor does he wish to make purely 

 academic distinctions in the treatment of data. In particular, 

 he does not wish to be understood as maintaining that congenital 

 cataract behaves strictly as a single dominant unit character — 

 a view to which he does not subscribe. The point upon which he 

 does insist, however, is that the view, presented in the paper 

 under discussion, namely that congenital- cataract is due to a 

 single recessive character, not only fails to find support in the 

 data which was presented, but is in reality actually disproved 

 by that data. 



C. H. Danforth 



Washington University Medical School 



