210 M. F. GUYER AND E. A. SMITH 
3A1, and the six young born November 23rd had normal eyes. 
On October 22nd, 26A6 was mated to 28A4 (both eyes defective) 
and gave birth to seven young, on November 24, 1919. In this 
litter one female had a left eye smaller than the right and the lid 
so covered it that details could not be made out. Another female 
had a small left eye with an opaque lens (fig. 7). 
Thus four individuals have been secured, so far, with defective 
eyes that came through the male line. It seems needless to say 
that the normal females used had first been tested with other 
males and the progeny remained normal through the several 
generations obtained. Since the defect in question passes down 
through the male line as well as through the female line, it is 
clearly a case of true inheritance. 
One other result merits attention here. To a female, 22, 
treated with chicken serum sensitized to rabbit lens, a litter of 
six, series 23A, was born on March 7, 1918. None of the indi- 
viduals showed any eye abnormality, but they were kept until 
mature, whereupon 23A6 was bred to 23A5, her brother (fig. 4). 
On December 11, 1919, she had three young, two of which died 
immediately. The remaining one never opened the eye on the 
right side, although it lived until January 2, 1919. Dissection 
showed the eyeball to be considerably smaller than that of the 
open eye. Next, 23A3 was mated to 23A2; the five young born 
January 3rd all had normal eyes. Another litter of five from the 
same parentage born on May 22, 1919, were likewise normal. 
Also, 23A4 was mated to 23A5, and the six young born January 
23rd, 1919, were normal. One male from this litter fathered 
another litter of five born to 23A4, July 19, 1919, all normal. 
Before closing the section on inheritance, it seems desirable to 
call attention again to the facts brought forward on pages 171 and 
173 regarding the safeguards employed to eliminate the possibility 
of the defect’s being originally a mere chance variation in a 
single stock. To these facts should be added the further one 
that scores of young have been obtained by the same males from 
the sisters of the females treated with sensitized serum and no 
kind of eye defect has ever appeared, although the intensive 
breeding practiced certainly gave every recessive factor a chance 
