EXPERIMENTAL EVIDENCE CONCERNING THE 



DETERMINATION OF POSTURE OF THE 



MEMBRANOUS LABYRINTH IN 



AMPHIBIAN EMBRYOS 



GEORGE L. STREETER 



Department of Anatomy, University of Michigan 



THIRTY-EIGHT FIGURES 



The purpose of the present paper is to report a series of experi- 

 ments that substantiate the conclusion that the posture of the 

 membranous labyrinth and the position of its canals is determined 

 by some force or influence that interacts between the labyrinth 

 and its environment. The exact nature of this control or in- 

 fluence has not yet been determined, but from the experiments 

 that are to be described it is evident that it possesses a force capa- 

 ble of producing a complete rotation of an embryonic vesicle that 

 has been displaced in a reversed position. 



The existence of a postural influence of this kind introduces a 

 new factor in organogenesis. It means that organs do not develop 

 inertly in the position that they happen to find themselves ; on the 

 contrary, there is a certain amount of adjustment of position 

 through forces interacting between them. According to the 

 conception of what we might call the theory of passive organ 

 development, all organs develop passively in the position in which 

 they are located at the outset. Perfect form according to this 

 theorj^ is eventually obtained because originally the anlages of the 

 various organs are so perfectly placed, and all the stresses so care- 

 fully calculated, that the subsequent increase in size, and mutual 

 pressure against each other, produce a final normal disposition of 

 all of them. In contrast to this we may now speak of self-place- 

 ment of organs or individuality of organ development, according to 



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THE JOCRN'At- OF EXPERIMENTAL ZOOLOGY, VOL. 16, NO. 1 



