Warren Harmon Lewis 481 
chyme between the small lens-buds and eye, as seen in Figs. 25, 27, 30, 
34, 35, 57, and 58 is an additional factor in causing these abortive 
lenses. Some of these lens-buds would probably have remained attached 
to the ectoderm for many days, while others, such as shown in Figs. 
21, 26, 27, 31, 32, 33, 36, and 37 might ultimately have separated, to form 
small solid spherical masses, as shown in Figs. 40, 41, and 42. Figs. 14, 
15, and 17 show how the mesenchyme may grow in between the early 
lens-plate and the optic vesicle. These lens-plates would probably have 
soon ceased to develop and small lens-buds have formed from them. 
Somewhat larger regenerating eyes give rise to larger lens-buds and 
vesicles, as in Figs. 60, 61, 62, 63, 64, 65, and 67. When such lens- 
structures retain more normal relations with the optic cup they will 
develop into small but fairly normal lenses, as in Figs. 71 and 72. 
The larger regenerating eyes give rise to more normal lenses, as in 
Figs. 69, 73, 74, and 76. 
These experiments indicate that the lens is neither self-originating 
nor self-differentiating, but is dependent for its origin, its size, its differ- 
entiation, and its growth on the influence of the eye. 
Abortive Lens-formation with Degenerating Eyes. 
Among these experiments there are four rather fortunate examples of 
degeneration and partial disintegration of the brain and the eye on 
the unoperated left side of the head. Three of these embryos were 
operated upon for extirpation of the right eye in succession and were 
killed 4 days after the operation. The fourth (DL,) was operated upon 
at an earlier time. In each the supposedly normal eye is much smaller 
than a normal one of the same age, and shows only shallow invagination, 
no differentiation of the layers of the retina except the outer pigment 
layer. Compare Figs. 79, 80, 81, and 82 with a normal eye (Fig. 77), 
from an embryo killed 4 days after the operating stage and of about 
the same age. The important point in connection with these degener- 
ating eyes is in the size and differentiation of the lenses. Instead of a 
large lens, as in Fig. 77, with long lens-fibers and a well developed 
epithelial layer we have only small lens vesicles. In experiment, DL,, 
there are two such lens vesicles (Figs. 81 and 82) associated with the 
same eye. The lens vesicles, although small and retarded in differen- 
tiation, show no signs of degeneration. ‘They are very similar to some 
of the small lens vesicles associated with small regenerated eyes (com- 
pare with Figs. 60, 61, 62, 63, 64, and 65). What I imagine has taken 
