Bie M. F. GUYER AND E. A. SMITH 
modification—that is, a change produced in the lens of the 
uterine young which in turn has induced a change in the lens- 
producing constituents in the germ cells of these young—or as 
simultaneous changes in the eyes and in the germ cells of the 
young. In either case the inference is that there is some consti- 
tutional identity between the substance of the mature organ in 
question and its material antecedents in the germ. 
Against the first supposition is the fact that in one case, at 
least, a defective-eyed individual was produced from a father 
and mother, each of which had eyes that appeared normal, 
though these parents were in utero at the time their own mother 
was treated with lens-sensitized serum. In this instance it 
would seem that changes had been induced in the eye factors in 
the germ cells of one or both of these uterine young, although 
their own eyes had remained unaffected. It is possible, of course, 
that changes—for example, liquefaction without opacity—had 
occurred in their eyes, but had been undetected by the observers. 
Again, in some instances defective-eyed young have been secured 
from one defective-eyed parent and one apparently normal-eyed 
parent, where the latter came of defective-eyed stock, or was in 
utero when the mother was being treated with serum containing 
lens antibodies, whereas the same defective-eyed parent bred to 
rabbits of normal ancestry yielded young with normal eyes only. 
In such cases it would seem that the apparently normal parent 
had had changes made in its germ cells by the sensitized serum, 
even though these had not been manifested in its own eyes. 
Lastly, the fact that among the progeny from two normal-eyed 
individuals of the defective line young with abnormal eyes may 
appear (fig. 5), after the manner of an extracted Mendelian re- 
cessive, indicates that whatever its origin the abnormality be- 
comes a germinal constituent which no longer requires expres- 
sion in the immediate parental body to call it forth. 
On the other hand, if the lens antibodies acted directly on the 
germ cells of the fetal young, then one would have every 
reason to expect that they would also act directly on the germ 
cells of the mothers originally treated with the antilens serum; 
but there is no evidence that such is true. Nearly every female 
