TRANSMISSION OF INDUCED EYE-DEFECTS 173 
facts all show that among mammals, rabbits are fairly favorable 
for breeding experiments, the fact that influenced us more than 
any other in choosing them is that in our experience they are 
physiologically well stabilized and rarely if ever in the course of 
ordinary breeding produce abnormal young. It is well known, 
for instance, that guinea-pigs of supposedly normal origin occa- 
sionally throw defective young. Sometimes it is a missing toe or 
toes, or perhaps there are extra toes. Again it may be some nerv- 
ous defect, such as congenital palsy or epileptic-like seizures, or 
perhaps, though less frequently, the defect is an eye anomaly. 
In breeding experiments carried on with guinea-pigs in the de- 
partment of genetics in the University of Wisconsin during the 
last few years several examples of the abnormalities just men- 
tioned have been encountered. In rats, also, the writers have 
seen two cases in which one eye was smaller than the other and 
was otherwise imperfect. 
As regards rabbits, however, we have never seen nor heard of 
such sporadic eye defects. The senior author has bred many 
rabbits for laboratory purposes and he has also conferred with 
a number of rabbit breeders, but has found no record of congeni- 
tal eye defects. In this connection some two years ago he made 
special inquiry of Dr. Orren Lloyd-Jones, of Ames, Iowa, a trained 
geneticist, who stated that in the four hundred and some odd rab- 
bits he had just been using in genetical problems he had observed 
nothing similar to the eye defects induced in our serum-treated 
stock. He also said that as a result of his various experiments 
in breeding rabbits, extending over a number of years, he had 
come to regard them as exceptionally stable forms. Likewise 
Dr. E. C. Rosenow, of the Mayo Clinic, who is constantly work- 
ing with rabbits and has done so for years, after looking over our 
experiments told us that he had never seen such eye defects in 
any of his rabbits. 
All testimony that we have received, therefore, coincides with 
our own experience that rabbits are stable forms whoily unlikely 
to develop eye defects unless, as in our work, these have been de- 
liberately induced by the experimenter. We dwell upon this 
point because when unusual results are obtained, the first thought 
