402 URBAN PRITCHARD. 



perforated for the passage of the cilia. I am very much 

 surprised that none of the previous, investigators should 

 have described this membrane; it is true that Ebner and 

 Meyer hint at something of the kind, but the other authors 

 appear to ignore it entirely. I can only account for this by 

 the fact that in foetal preparations this membrane cannot be 

 made out. 



This cuticular membrane is undoubtedly analagous to the 

 reticulate membrane of the organ of Corti, and I therefore 

 propose calling it by the same name — membrana reticularis. 



Having described the type of the nerve-epithelium, I now 

 pass on to its modifications. As there is a general increase 

 in the thickness of the macula from circumference to centre, so 

 the cells and their various parts elongate ; the cilia, which 

 are short and stumpy at the edge, become very much longer 

 and comparatively finer at the centre of the acoustic spot. 



Round the border of the spot the cells pass by insensible 

 gradations into the columnar form of the epithelial cells 

 which surround it. In this change the double nature of the 

 cellular elements is very apparent. 



Towards the centre of the acoustic spot the upper nucleus 

 and surrounding protoplasm of the bristle-cells gradually 

 diminish, and then are lost altogether, the cell being repre- 

 sented by a trabecula from the membrana reticularis, taper- 

 ing downwards towards its second or lower nucleus. The 

 bristle-like cilium remains after the upper protoplasmic mass 

 has disappeared, but eventually this also is lost. Curiously 

 enough, as this atrophy of the cell is proceeding, the bristle- 

 like cilium appears to go out of its course to approach nearer 

 and nearer to its neighbouring thorn, so that towards the 

 centre of the acoustic spot the two cilia are seen lying close 

 together, and almost appear to proceed from one and the 

 same cell. 



I think this description bears out what I just stated, that 

 my observations tend to reconcile the opposing views of 

 previous writers. 



Naturally, the lower layer of nuclei has been recognised 

 by all except Rlldinger, who seems to have been unfortunate 

 on this point. 



The isolating cells of Hasse and triangular ones of 

 Riidinger are represented by my bristle-cells, no one having 

 previously observed their cilia, or, indeed, that there were 

 were two forms of cilium. Again, these cells, where they 

 lose their upper nucleus, correspond to the filiform cells of 

 Max Schultze and Ebner. 



Jliidinger's description is very like what may be seen in 



