Il6 AYERS. [Vol. VI. 



thickened and characteristically striate somewhat after the fash- 

 ion of the ^^ Randsajivi " of the intestinal epithelial cells. 



The number of hairs to a cell varies within considerable limits. 

 The limits as I have found them up to the present are ten as a 

 minimum and thirty as a maximum. Of the whole number of 

 counts made twenty-five was the average. These figures are 

 for the ox, pig, and rabbit. I am not sure that a variation in 

 the size of the hairs is connected with the variation in number, 

 nor do my observations suffice to determine whether the smaller 

 cells bear the smaller number of hairs, and the larger cells the 

 greater number of hairs. The hairs borne by the same cell 

 appear to vary in size at their bases, but in objects so minute 

 it is hazardous to draw conclusions from other than very exten- 

 sive series of observations. The hairs themselves when seen 

 free from the cell cap do not show noticeable variations in size, 

 so that I am inclined to the opinion that the apparent variation 

 in size, as seen on the cell cap, is due to optical conditions, e.£: 

 such as the greater or less refraction of light by the hair bases 

 depending upon their position. 



In glycerine preparations of the cochlear sense organ of a 

 young calf, and in similar ones of a new-born rabbit, the mem- 

 brana tectoria is easily resolvable into its component layers. 

 Two plates are specially easy to be distinguished, and they in- 

 clude between them the canal of Corti and the pillar cells, in 

 that they arise from the outer and inner hair cells respectively 

 and fuse together above the cochlear organ, but only after they 

 have arched beyond the median line of the canal of Corti and 

 its pillar cell rows. 



Each plate as it passes down to the cells of the inner and 

 outer hearing cells splits up into portions which end one in 

 each sensory hair cell. The number of hairs passing into a 

 cell I could not determine, but it is safe to say it is above eight. 

 Owing, however, to the fact that the hairs appear to have the 

 power of splitting up indefinitely, it is almost impossible to get 

 accurate and trustworthy data of the number of hairs connected 

 with a single cell. 



The whole course of the individual hairs is very difficult to 

 follow. In radial sections the hairs are invariably cut across, 

 owing to their oblique course in the band, a single hair crossing 

 obliquely a space measuring 0.013-l-mm. Hairs do not ascend 



