POSTURE OF MEMBRANOUS LABYRINTH 151 



vesicle, is not controlled by the en\'ironment but is determined by 

 the intrinsic character of its own constituent cells. A left-sided 

 ear ^-esicle when transplanted to the right side de\'elops into a 

 labyrinth having all the characteristics of a left-sided organ; the 

 anterior canal is formed on the caudal border of the labyrinth, the 

 posterior canal on the oral border, and the lagena, which normally 

 is directed caudalward,is found extending forward toward the eye. 



It was found, however, that the ear vesicle, though capable of 

 this marked power of self -differentiation, apparently was not in 

 all respects independent of the surrounding structures. The 

 posture of the developed labyrinth, the situation of its canals and 

 various chambers, seemed to be controlled by the environment. 

 Deliberate rotation of the ear vesicle into abnormal positions and 

 even transplantation to the opposite side of the body, always 

 resulted in a labyrinth possessing a normal attitude with reference 

 to the brain, ganglion masses, and the surface of the body. In 

 all of seventeen experiments performed for this purpose the results 

 were positive, and the writer consequently came to the conclusion 

 that there is some influence interacting between the ear vesicle 

 and its environment that constitutes the chief factor in the deter- 

 mination of its placement. 



At the same time an experienced foreign investigator had been 

 working independently upon a sunilar problem (Spemann '06 a 

 and '06 b). His experiments consisted in removing the ear vesi- 

 cle in young Rana esculenta larvae and then replacing it in an in- 

 verted position for the purpose of studying the consequent abnor- 

 mal body movements and their coi relation with the anatomical 

 results of the operation. He also studied the influence of the epi- 

 thelial labyrinth upon the surrounding connective tissue, and its 

 relation to the formation of the cartilaginous and bony labyrinth. 

 Concerning this latter problem he did not come to a definite con- 

 clusion. The former problem, however, gave positive results. He 

 found that the inverted vesicle continued in its development and 

 formed a more or less complete labyrinth, but, unlike my speci- 

 mens, the orientation of the developed labyrinth corresponded to 

 the operative displacement of the vesicle. There had been no 

 subsequent readjustment of position. After the appearance of 



