254 Origin and Differentiation of the Lens 
after removal of the optic cup. Hence, whatever retardation of the 
lens rudiment may occur is not to be ar by the immediate results 
of the operation. 
In an embryo (Experiment XII,,) ‘alled six days after the operation, 
the right lens (Fig. 28) is somewhat smaller than the left one (Fig. 27). 
It is rather normally developed and contains some healthy lens-fibers 
which have arisen from the medial pole. The pole, as it now appears, 
is not as broad as normal, but is becoming obliterated by the overgrowth 
of the layer of columnar epithelium, which surrounds the central mass 
of lens-fibers. Had the embryo lived longer, no doubt the medial pole 
would have entirely disappeared, and thus the lens would have been com- 
jetely surrounded by this layer of epithelium, as in the following ex- 
periments. 
Great retardation is shown in four of the experiments (XII; 55 50 57) 
of this series (XII), of which two of the embryos were killed 10, and 
the other two 12 days after the operation. The right lenses are entirely 
surrounded by a single layer of cuboidal epithelium, and the medial poles 
from which the lens-fibers within had been formed are completely ob- 
literated. The right lenses are rather small, and are not widely sep- 
arated from the ectoderm. The lens-fibers adjacent to the epithelial 
covering seem rather healthy, while the central mass appears degenerated, 
but takes a similar protoplasmic stain. These lenses, then, differ con- 
siderably in structure as well as in size from the normally developed 
ones (Fig. 26, and compare Fig. 9). 
In an experiment (XII,,) where the embryo was allowed to live 30 
days, a bit of the optic cup had remained, but its influence, if any, did 
not long continue, for the right leris developed until it was only 150 p 
in diameter, and then came to a standstill, and the lens-fibers within 
degenerated. A thin epithelial covering surrounds this vacuolated mass 
of degenerated fibers which are in marked contrast to the healthy fibers 
of the left lens. The normal lens measures about 250 » in diameter, and 
thus shows considerable difference in size from the right one. In the 
experiments which continued over long periods of time, especially for 
30 days, one is impressed not only with the retarded development of 
the right lenses, but also with the marked degeneration of the more 
highly differentiated lens-fiber tissue. 
In three other embryos (Experiments XIJ,, 4. 4)) of this same stage 
(XII), the right lenses somehow came into contact with the nasal pits 
on their respective sides. The lenses have developed rather normally. 
It is possible that this peculiar arrangement was brought about by the 
operation. The skin flap perhaps became somewhat twisted, thus throw- 
ing the medial pole of the lens into contact with the nasal pit, which 
