AND HAIR-CELLS IN THE DEVELOPING ORGAN OF OORTI. 137 



Supporting elements is, therefore, repelled inward and ultimately incorporated into 

 and completing the superficial sustentacular interstices, which already contain the 

 phalanx processes of the supporting elements, (c) This shifting is facilitated by 

 the previous transference of the phalanx processes and by the peculiar connections 

 between the lower pole of the hair-cells and the subjacent spiral nerve bundles. 



8. Pressed out from their original mixed row, and having reached their respec- 

 tive interstices, the phalanx processes of the first and second rows of Deiters cells, 

 together with those of the third row, undergo a shifting in a spiral direction, their 

 apices moving from a basal to a more apical portion of the cochlea, so that they 

 cross three hair-cells in their course towards the membrana reticularis. Whereas 

 the acoustic elements follow a nearly vertical course, the cell bodies, and particu- 

 larly the phalanx processes of the cells of Deiters, run more obliquely (figs. 19, 19'). 

 This spiral shifting is due to an unequal development or extension towards the apex 

 of the cochlea of the two membranse to which are attached the two extremities of 

 the cells of Deiters, the membrana reticularis extending more rapidly than the mem- 

 brana basilaris. 



9. The third stage of development is preceded by a considerable elongation of 

 the nucleated cell bodies of the elements of Deiters and the appearance of a peculiar 

 portion the segment of support or sustentacular segment. On lengthening out 

 obliquely from the nucleated part of the cytoplasm towards the lower pole of the 

 hair-c.ell which will eventually be supported by it, the apex of the cell body enlarges 

 and extends into a long segment surmounted by a cup-like depression surrounding 

 the lower pole of the acoustic element; so that the axes of the hair-cells of the first, 

 second, and third spiral rows ultimately blend respectively with those of the cells 

 of Deiters of the first, second, and third rows. 



10. Lateral to the spiral row of inner pillars the final structure of the organ of 

 Corti is composed of the following supporting and mixed spiral rows: The row of 

 outer pillars; the first mixed row of superficial acoustic elements supported by the 

 subjacent bodies of the cells of Deiters; the superficial interstice containing the 

 phalanx processes of the Deiters cells of the first row; the second mixed row of 

 superficial acoustic elements supported by subjacent bodies of the cells of Deiters; 

 the superficial interstice containing the phalanx processes of the cells of Deiters of 

 second row; the third mixed row of superficial acoustic elements supported by the 

 subjacent bodies of the cells of Deiters; and the superficial interstice containing 

 the apical processes of the cells of Deiters of the third row. 



11. At the third and final stage of development the spiral nerve bundles be- 

 tween the cells of Deiters, which originally were situated lateral to the primitive 

 outer mixed rows (fig. 3, N lii , N iv , N v ) occupy a place inside of the mixed spiral rows 

 (fig. 9, N iu , N iv , N v ). 



12. The supporting apparatus of the cells of Deiters is originally formed of a 

 stem or paraxial fibrillated filament, running straight throughout the inner portion 

 of the prismatic cell body, at the apex of which it curves around and continues as an 

 oblique apical fibrillar filament in the phalanx process of the cell. In later stages 



