86 CARNEGIE INSTITUTION OF WASHINGTON. 



Membranous Labyrinth. 



In the course of some experiments carried out several years ago 

 with amphibian larva?, I discovered that the cells constituting the 

 ear-vesicle are specialized very early and that, when transplanted to 

 an abnormal environment, they continue to differentiate in the usual 

 way into a recognizable labyrinth. Even fragments were found to 

 develop independently of the rest of the vesicle, and an individual 

 part, such as the endolymphatic appendage, might be quite normal 

 in cases where the remainder of the labyrinth was very abnormal. 

 It was further found that the developmental independence of the 

 vesicles extends to differences existing between a right-sided and a 

 left-sided organ. The dextral or sinistral character of the ear-vesicle 

 is not controlled by its environment but by the intrinsic character of 

 its own constituent cells, and a left ear-vesicle, when transplanted to 

 the right side, develops into a labyrinth having all the characteristics 

 of a left-sided organ. It was found, however, that the ear-vesicle, 

 though capable of this marked power of self-differentiation, was 

 not in all respects independent of the surrounding structures. The 

 posture of the fully developed labyrinth and the position of its canals 

 were found to be controlled by the environment. Deliberate rotation 

 of the ear-vesicle into abnormal positions, and even its transplantation 

 to the opposite side of the body, resulted in a labyrinth possessing a 

 normal attitude with reference to the brain, ganglion masses, and the 

 surface of the body. Regardless of the manner of its displacement 

 at the time of the operation, the labyrinth seemed always to correct 

 its position, even to the extent of complete rotation. The existence 

 of a postural influence of this kind introduces a new factor in organo- 

 genesis, concerning the nature of which we know very little. It 

 forces the conclusion that the labyrinth does not develop inertly in 

 the position in which its rudiment first lies, subject only to mechanical 

 stresses of the adjacent structures, but that we must also take into 

 consideration an autostatic tendency inherent in the vesicle itself, by 

 virtue of which it maintains and accurately adjusts its position during 

 the course of development. 



In substantiation of the above conclusion, I have been able to show 

 during the past year, from a study of normal material, that not only 

 does this adjustment of position occur under artificial conditions of 

 experiment, but that in the ordinary course of development the ear- 

 vesicle undergoes a recognizable migration or change of position, 

 moving from the point of its original attachment to the skin to a more 

 median and dorsal location, where it adjusts itself closely against the 

 side of the brain in a definite attitude. 



Other experiments on the ear-vesicle of amphibian larvse were made 

 by Professor C. Ogawa, while a guest of this laboratory, in order to 

 determine, if possible, how soon the ear-vesicle rights itself after an 



