LENS-FORMATION FROM STRANGE ECTODERM IN RANA 
SYLVATICA. 
BY 
WARREN HARMON LEWIS. 
From the Anatomical Laboratory, Johns Hopkins University. 
WitH 70 FIGURES. 
That the optic vesicle can stimulate a lens to arise from ectoderm 
other than that which normally gives rise to one I have already demon- 
strated in rana palustris. Several methods were here employed, that 
of transplantation of the optic vesicle into other regions of the body 
being the most successful. Only the earlier stages of lens-formation 
were shown in these experiments and it has seemed desirable to demon- 
strate in another species this origin of the lens from strange ectoderm 
and also to ascertain if such lenses from strange ectoderm are capable of 
development into normal lenses. Rana sylvatica, a common species of 
this region, has proved a very suitable animal for such experimentation. 
The right optic vesicles of 74 embryos were transplanted each into the 
otic region of the same side of the same embryo, from which they were 
removed with remarkable success as concerns the formation of lenses 
from the ectoderm over the region into which the eye was transplanted. 
I have already discussed the lens-formation in the normal region asso- 
ciated with regenerating eyes in this species as well as in rana palustris.” 
Here it was clearly shown that a lens will not arise from the normal 
lens-forming region of the ectoderm without the contact stimulus of the 
optic vesicle on the inner layer of the ectoderm, the lens is not a self- 
originating structure, nor is it a self-differentiating structure, as abortive 
lens-formation follows when the normal relations between lens and eye 
are disturbed in rana palustris and rana sylvatica and in amblystoma.° 
It also seems, probably, from a study of the regenerating eyes that only 
the retinal portion of the eye is capable of stimulating lens-formation, 
Am. Jour, of Anat., Vol. TL, p37 505: 
2 Am. Jour. of Anat., Vol. VI, p. 473. 
>Le Cron, Am. Jour. of Anat., Vol. VI, p. 245. 
AMERICAN JOURNAL OF ANATOMY.—YOL. VII. 
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