6 HOVLE, PterygioteutJiis niargaritifera. 



moreover they do not stain quite so deeply. These inner 

 scales are seen in tangential sections {Fig. 4) to be discs 







"=0 



Fig. 4. 



A few of the scales from a tangential section of the 

 posterior cup ; n, nerve. 



of varying shape, recalling flattened epithelial cells. 

 Sometimes they are nearly flat, as in the outer layers ; 

 sometimes they are hollowed into a shallow dish-like shape, 

 where they fit round the central spheroid of the cone {^Fig. 3). 

 They thin out remarkably at their edges, and in some cases 

 the fine lines produced by these thin edges seen in section 

 appear to run very close to the adjoining bodies, but I have 

 not been able to find any instance in which they are 

 actually connected. 



The bodies occupying the outer layers of the cup are, 

 as above indicated, distinguished by a deeper coloration, 

 and by more irregular wavy outlines. They are on the 

 whole decidedly thinner, especially in the outer Ia3ers 

 Hearing the equator of the organ, whilst towards the edge 

 of the cup they lose, to a large extent, their concentric 

 arrangement, and exhibit a tendency to dispose themselves 

 in lines radiating outwards. In internal structure, too, 

 they are much more granular. 



As to the nature of these bodies forming the cup I 

 feel some uncertainty ; it seems to me quite clear that 

 they are not cells, for I have been unable to find a nucleus 

 in any of them. It is true that some have a distinct body 

 in the centre, but this has apparently no structure, and it 

 appears to me most likely that they are composed of 



