A SHORT REMARK UPON W. H. LEWIS' " EXPERI- 

 MENTAL STUDIES ON THE DEVELOPMENT 

 OF THE EYE IN AMPHIBIA." 1 



ALFRED SCHAPER, 

 UNIVERSITY OF BRESLAU, GERMANY. 



In the above-mentioned article, published in Volume III. of 

 the American Journal of Anatomy (1904), W. H. Lewis has given 

 us the results of a large number of ingenious experiments on 

 frog-larvae intended to determine the possible correlations be- 

 tween the development of the optic vesicle and that of the lens. 



These experiments have, in the first place, offered a new and, 

 as it seems to me, very convincing proof that there is indeed, as 

 first maintained by Herbst and Spemann, a distinct correlation in 

 the development of these two organs, namely in such away " that 

 in normal development the lens is dependent for its origin on tJic 

 contact influence or stimulus of the optic vesicle on the ectoderm." 



Furthermore Lewis has, by transplanting the optic vesicle to 

 another part of the larval body, demonstrated " that the optic 

 vesicle can stimulate a lens to form from various portions of the 

 ectoderm and even from the ectoderm from tJie abdomen of another 

 species of frog; . . ." From this fact he has drawn the follow- 

 ing conclusion : " There is no predetermined area of the ectoderm 

 which must be stimulated in order that a lens may arise. On the 

 contrary various portions of the skin when stimulated by the con- 

 tact of the optic vesicle may and do give rise to a lens. Not only 

 will a lens arise from various places on the skin as a result of the 

 contact of the optic vesicle of the same animal, but the optic 

 vesicle of one species may cause a lens to rise from the ectoderm 

 of another species of frog." This latter result of Lewis' experi- 



1 Lewis, W. H., " Experimental studies on the development of the eye in Amphi- 

 bia. I., On the origin of the lens, Rana palustris,'' American Journ. of Anatomy, 

 III., 1904. 



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