Warren Harmon Lewis 483 
on the ectoderm. The larger ectodermal bodies form yesicle-like struc- 
tures, as in Figs. 52, 53, 54, 55, and 56. Some of these bear a-very 
close resemblance to small lens vesicles, associated with small regenerating 
eyes. 
This marked similarity between some of the early abnormal lens-buds 
or vesicles and those caused by injury suggest, of course, the idea that 
the initial stimulus of the optic vesicle on the ectoderm is one which 
merely causes those cells of the inner layer to multiply more rapidly 
than normal. The cells of the inner layer of the ectoderm seem to 
have the power of responding to the stimulus of the optic vesicle, or 
to the mechanical stimulus of the point of a needle, by increased rate 
of cell division. There is also a tendency for these groups of cells to 
hold together in the form of buds, or spherical masses, the latter being 
hollow when large, forming vesicles. In many of the embryos, especially 
in rana sylvatica, these injury processes are often very long and large 
and seem to result partly from accidental transplanting an attached 
piece of ectoderm into the mesenchyme; they may extend for ‘long 
distances into the mesenchyme, and when caudal to the otic capsule often 
unite with the pharyngeal epithelium. When they occur in the region 
of a regenerated or transplanted eye, the entire process, or only a portion 
of the process, may undergo transformation into a lens, provided it 
comes into contact with the eye, but not otherwise. These will be con- 
sidered later in connection with lens-formation from transplanted eyes. 
DIscussION OF RESULTS FROM THE EXPERIMENTS. 
Is the Lens Self-originating ? 
These experiments point very clearly to the lens not being a self- 
originating structure. Its entire absence after total extirpation of the 
optic vesicle without regeneration of the eye, and its absence in many 
of the embryos with small regenerating eyes are very conclusive evidence 
in favor of this view. The small abortive lenses with small, irregular, 
regenerating eyes and the evident dependence of the lens for its growth 
and differentiation on the continued influence of the optic cup, and 
Le Cron’s experiments on amblystoma showing that the lens is dependent 
on the continued influence of the optic cup for its growth and differen- 
tiation even after it has separated from the ectoderm, also support this 
view. 
These results are not in accord with the conclusions of King.” On 
’ Experimental Studies on the Eye of the Frog. Arch. f. Entwirklungs- 
merk. d. Organ., XIX, 1905. 
