410 Charles R. Stockard. 
recorded (09), that free lenses arise in their usual lateral positions 
while the eyclopean eye possesses its lens of anterior origin. 
In the fish embryo the optic vesicle may cause a lens to form 
from ectoderm far removed from the usual lens-forming area, 
and rarely in such cases it happens that free lenses may also 
arise from the usual lens-forming region. 
| Does a Deeply Buried Eye have the Power to Regenerate or Form 
A Lens from its own Tissues? 
It has been shown by many experimenters Colueci (91), Wolff 
(95 and ’01), Miller (96) and Fischel (02), that the salamander’s 
eye regenerates a new lens from the posterior surface of the iris 
when the old lens is removed, or as Fischel found, if the old lens 
be merely pushed back out of its usual placeinthe eye. When the 
iris was injured in two places during the extirpation of the lens, 
two lenses arose within the single eye, one growing from each 
injured area of the iris. It has also been found that a fish’s 
eye would regenerate a lens under certain conditions: when the 
fish is young and when a sufficiently long time is allowed for the 
lens to regenerate. 
Lewis (04) finds that the deeply buried eyes in Rana palustris 
which fail to come in contact with the ectoderm are unable to 
form lenses from their own tissues. While on the other hand he 
states that in a second species, Rana sylvatica, the optic cup 
readily gives rise to a lens from its own tissues if prevented from 
stimulating the formation of a lens from the ectoderm of the body 
wall. 
The fish embryos which are now being considered, act in a 
similar manner to Rana palustris and are unable to form lenses 
from the tissues of their optic cups. Whenever the optic cup 
is deeply buried and fails to reach the ectoderm it also fails to 
possess a lens, as is illustrated on the left side of figs. 26, 27 and 
28. In this connection it may be mentioned that Morgan was 
unable to obtain the regeneration of a lens in adult specimens 
of Fundulus, although as mentioned above, lenses do regenerate 
in the eyes of another species of fish. 
