EXPERIMENTAL STUDIES ON THE DEVELOPMENT OF 
THE EYE IN AMPHIBIA. 
III. ON THE ORIGIN AND DIFFERENTIATION OF THE LENS. 
BY 
WARREN HARMON LEWIS. 
Associate Professor of Anatomy, Johns Hopkins University. 
WITH 83 FIGURES. 
INTRODUCTION. 
Since the publication of my paper on the origin of the lens in rana 
palustris," I have made many new experiments on lens-formation with 
regenerating and transplanted eyes, not only in rana palustris but in rana 
sylvatica and amblystoma punctatum. My pupil, Mr. Le Cron, has 
also made experiments in the same field on amblystoma.* These new 
experiments confirm the conclusions given in my previous paper for 
rana palustris and throw additional light on the origin and early de- 
velopment of the lens. They leave no doubt, I believe, but that a lens, 
arising from the ectoderm in the amphibian embryo, is dependent for 
its origin on the contact infiuence of the optic vesicle on the ectoderm, 
in other words, the lens is not a self-originating structure. These 
experiments indicate that actual contact between optic vesicle and ecto- 
derm is essential, and that the optic vesicle has not the power of acting 
at a distance to stimulate lens-formation. The size of the lens-plate, the 
lens-bud, the lens vesicle, and the early stages of the lens are shown 
to be dependent in part upon the actual area of this contact between 
optic vesicle and ectoderm. These experiments indicates also that not 
only is the lens dependent on the influence of the optic vesicle for its 
initial origin, but that its subsequent growth and differentiation is 
dependent on the continued influence, probably contact influence, for a 
time at least, of the optic vesicle. Le Cron’s experiments were directed 
more especially towards this point and show that in amblystoma the 
influence of the optic vesicle must be exerted for a considerable period 
1Am. Jour. of Anat., Vol. III, 1904. 
2Am. Jour. of Anat., Vol. VI, 1907. 
AMERICAN JOURNAL OF ANATOMY.—VOL. VI. 
