ig5 AYERS. [Vol. VI . 



later on they acquire two nuclei, and then divide transversely, in 

 each case producing an upper or surface hair cell and a lower or 

 buried auditory cell, which is not hair-bearing. The former is 

 Boettcher's "absteigende Horzelle," which is fixed to the mem- 

 brana reticulata, in whose separate existence Boettcher fully 

 believed, while the latter cells were called by him the "auf- 

 steigenden Horzellen " or supporting cells, and were fixed to the 

 basilar membrane. Their most rapid development takes place 

 about the time of birth. In some animals it begins before 

 birth, but in the majority the impulse to special growth is not re- 

 ceived until after they come into the air. The cells then begin 

 to elongate rapidly and soon divide. Their protoplasm acquires 

 a complication of structure not yet fully worked out, and only 

 partially understood. Boettcher found that in hair cells immersed 

 in aqueous humor there was to be seen only a transparent pro- 

 toplasm evenly but finely granular, but in cells killed in other 

 reagents this transparent protoplasm was shown to possess a 

 very complicated structure. My observations on the continuity 

 of the capillo-nuclear fibres in the adult cells were made before 

 I had seen Boettcher's paper, and his observations are the only 

 ones in the literature of the subject which give us any details 

 of the development of these fibres. These cells contain a glass- 

 clear central fibre or cord which incloses the cell nucleus, and 

 is itself inclosed in a very delicate pale sheath. Henle, the only 

 other observer who has noticed this, supposed it was due to 

 coagulation by HCl ; but Boettcher has shown that most reagents 

 produce it. Boettcher thinks that a similar process occurs in 

 both rods and cells to produce these fibres, which he considers 

 perhaps identical. This central thread passes directly into the 

 thread from the membrana tectoria. When all the rest of the 

 cell is destroyed, one sees it as a naked bundle of fibrils united 

 to the nucleus. 



Although the cells of the large epithelial ridge are resorbed 

 without having shown the tendency to change their shapes or 

 sizes, the cells of the small epithelial ridge early undergo a 

 series of changes which transform them into the organ of 

 Corti. The row of cells lying in contact with the outer border 

 of the large epithelial ridge are changed into the row of inner 

 hair cells (they are from a very early period hair-bearing cells), 

 and bear long, strong hairs of the kind described in a preceding 



