132 ARRANGEMENT AND STRUCTURE OF SUSTENTACULAR CELLS 



bichromate, and staining by fuchsin and methyl-green, the superficial cuticula 

 appears homogeneous and, like the hairs, remains unstained. After fixation 

 with osmic vapors or osmic acid, and staining with iron hematoxylin, pale, clear 

 cuticulse may be observed. From these observations it would appear that the 

 chemical constitution of the hairs and cuticulse is somewhat different from that of 

 the original chondriosomes. Similar chemical changes have been noted in the devel- 

 opment and evolution of mitochondria! structures. Without emphasizing those 

 observed in gland-cells, it may be recalled that during the period of growth and 

 genesis of the yolk of the ovum the pseudochromosomes (O. Van der Stricht, 1904), 

 and the vitellogenic bands (1909), both mitochondria! in nature, undergo analogous 

 alterations. 



SUPPORTING CELLS. 



From the earliest stages of their differentiation (fig. 1) the pillar-cells (ip, op), 

 the inner (is 1 ) and outer (d) sustentacular cells contain numerous chondriomites, 

 and like the acoustic elements are longitudinally striated, owing to the longitudinal 

 disposition of the chondriosomes. The young cells of Deiters (d) possess a mitochon- 

 drial body in close contact with the lower pole of the nucleus. In more advanced 

 stages, before the appearance of coarser permanent structures, the arrangement 

 of the chondriosomes differs according to the nature of the supporting element. In 

 the inner sustentacular elements, within which no peculiar structures are formed, 

 the chondriomites remain scattered more or less regularly throughout the length of 

 the cytoplasm (figs. 9 and 15, is 1 ). 



As illustrated in figure 2, within the upper part of the pillar cells (ip, op) and 

 the cells of Deiters of the first (d 1 ) and second (d 11 ) rows, appears an axial, darker 

 granular strand which is mitochondrial in nature (fig. 4), formed of closely arranged 

 chondriomites. The band is surrounded by a clearer exoplasm within which the 

 chondriosomes are less numerous. In figure 4 this mitochondrial strand reaches 

 the base of all these sustentacular elements except that of the cells of Deiters of the 

 third row (d 111 ), and the clearer cytoplasm becomes obviously reticulated or vacuo- 

 lated, being pervaded by a network along which fewer mitochondria are scattered. 

 In the meshes of the network are seen vacuoles formed of a pale, more fluid material. 

 The mitochondrial bundle, longitudinally striated (figs. 15 and 9, ip) in vertical sec- 

 tions, occupies the portion of the protoplasm within which the supporting fibers will 

 appear in a more advanced stage (fig. 8, ip), these filaments being produced by a 

 fusion of the juxtaposed ends of the chondrioconts. 



In the inner pillar-cells the chondriomites become densely grouped around the 

 axial strand at the level of the apical portion of the cytoplasm, so that on cross- 

 section they form a mitochondrial ring or circle (figs. 3, 4, and 12, ip) inclosing the 

 central part of the band, within which they are thinly scattered. This ring corre- 

 sponds to the transverse section of a tube, the " Fibrillenrohre " of Held (1909), 

 developed according to that observer (p. 209) "von der freien Seite her und von 

 dem ganzen Rand und Umfang ihrer Schlussleisten." It would be more correct to 

 say that this mitochondrial tube extends from the superficial centrosome towards 



