170 GEORGE L. STREETER 



DISCUSSION 



The results that have just been recorded seem to show conclu- 

 sively that there exists some influence between the transplanted 

 ear vesicle and its environment that tends to control its posture, 

 and that an inverted vesicle is thereby rotated back into the nor- 

 mal position. At the same time we must recognize the fact that 

 Spemann ('10), from investigations of the same problem with 

 experiments of much the same character, came to quite different 

 conclusions. On examining and comparing our results, however, 

 it will be seen that they are not necessarily contradictory, as 

 thought by Spemann, but may perhaps be better described as 

 differing in degree. 



Including those in the present paper I have now reported 36 

 experiments in which the posture of the ear vesicle was especially 

 studied. In 12 of these the ear vesicle had been rotated 180 

 degrees from its normal position ; in 5 of them the ear vesicle had 

 been transplanted without special placement; and in 19 of them 

 the ear vesicle was transplanted and at the same time placed in 

 a definite abnormal posture. In all of these 36 cases the labyrinth 

 regained its normal posture. In Spemann's twelve reported 

 cases in which there had been simple inversion of the ear vesicle, 

 nine of the ear vesicles remained inverted, while two partially and 

 one completely regained their normal posture. The latter Spe- 

 mann regarded as an unsuccessful operation, surmising that it 

 had slipped back into position directly after the operation. The 

 fact of 'slipping' into the right position is the point of the whole 

 matter. It is the remarkable fact that an ear vesicle, though 

 rotated or turned or transplanted in an extremely abnormal posi- 

 tion, nevertheless 'slips' into the correct position, that I am trying 

 to establish in this paper. 



It is of interest to examine Spemann's methods in search of 

 some explanation for the difference in our results. For his ex- 

 periments he used Rana esculanta larvae while I used Rana 

 pipiens. It is not likely, however, that this would account for 

 the difference in our results. His operations were performed at 

 the time the ear vesicle is in the process of detaching itself from 



