Experimental Evidence concerning the Determination of Posture of the Membranous Labyrinth I N Amphibian Embryos

The purpose of the present paper is to report a series of experiments 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 influence has not yet been determined, but from the experiments that are to be described it is evident that it possesses a force capable 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 ad.justment of position through forces interacting between them. Ahcording 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 theory is eventually obtained because originally the adages of the various organs are so perfectly placed, and all the stresses so carefully calculated, that the subsequent increase in size, and mutual pressure against each other, produce a final normal disposition of all of them. In cont,rast to this we may now speak of seu-placeinent of organs or individuality of organ development, according to 149