From the Wistar Institute of Anatomy and Biology, Philadelphia 



SOME FACTORS IN THE DEVELOPMENT OF THE 

 AMPHIBIAN EAR VESICLE AND FURTHER EXPERI- 

 MENTS ON EQUILIBRATION 



BY 



GEORGE L. STREETER, M.D. 



Associate Professor of Neurology at the Wistar Institute 

 With Six Figures 



In a previous paper concerning experiments on the developing 

 ear vesicle^ it was shown that the group of cells forming the primi- 

 tive epithelial ear cup or ear vesicle of the tadpole is specialized 

 to that degree that although removed to an abnormal environ- 

 ment the cells still continue to differentiate themselves into a struc- 

 ture possessing many of the features of a normal labyrinth. Re- 

 cently it has been shown by Lewis^ that even earlier, while still an 

 uninvaginated plate, the ear anlage is already capable of a cer- 

 tain degree of independent differentiation. In the following paper 

 additional evidence will be given of the high degree of develop- 

 mental independence possessed by the early labyrinth cells. It 

 will be pointed out that individual parts of the vesicle may develop 

 independently of the rest of the vesicle. It will also be shown that 

 the process of differentiation extends to the difference existing 

 between a right and left-sided organ. A left ear vesicle trans- 

 planted into the empty pocket left by the removal of the right ear 

 vesicle develops into a labyrinth that is perfect in general form 

 and in its relations to the brain, with the exception that it main- 

 tains its left-sided character; the anterior semicircular canal is 

 found on the caudal side toward the vagus group, while the pos- 

 terior canal lies toward the eye, and likewise the lagena which 



* Streeter, G. L., '06: Some experiments on the developing ear vesicle of the tadpole with relation 

 to equilibration. Jour, of Experimental Zool., vol. iii. 



2 Lewis, W. H., '07: On the origin and differentiation of the otic vesicle in amphibian embryos. 

 Anatomical Record, No. 6, Amer. Jour, of Anat., vol. vii. 



The Journal of Experimental Zoology, vol. iv, no. 3. 



