18 Golding Bird and Schäfer, 



elongation of the peripheral portions of the cone -element. Now it 

 is noticeable in the specimens and well brought out in parts 

 of the photographs that these portions of the cone-elements are of 

 exactly the same size as the cones with which thay are continuous. 

 They are just as closely packed and are stained to precisely the same 

 extent, and there can be no doubt that they form morphologically 

 single structures. On the other hand the proximal parts of the cone 

 fibres have not the same uniformity of thickness. They are however 

 by no means the extremely fine linear fibres which they are repre- 

 sented to be in all the figures which we have above considered; that 

 of Cadiat alone excepted. 



6. As to the direction of the fibres in the fibrous layer of the 

 fovea and the relative thickness of this layer at different parts. 



In our specimens the most central fibres — those which are con- 

 tinuous with the cones which rest on the umbo of the external fovea 

 and which are really as above shown prolongations of the cone-bodies — 

 run perfectly vertically towards the outer molecular layer, upon which, 

 as we have seen, their nucleated bodies are almost sessile; the fibres 

 expand slightly as they pass to the nuclei. The opposite side of the 

 nucleated enlargement in those which are thus sessile, forms a kind 

 of triangular base from which fibres appear to diverge into the outer 

 molecular layer. A very short distance (some six or eight cones 

 width) from the centre the fibres begin to diverge obliquely outwards 

 as they pass towards the outer molecular layer, the obliquity being at 

 first slight but afterwards extreme, so that the outer ends of the 

 fibres are nearly horizontal. The fibrous layer is thinnest opposite 

 the centre of the fovea and from here gradually expands to the 

 margin of the fovea, where it is thicker than anywhere else in the 

 retina. Its depth from within out at the very centre, measured from 

 the limitans externa to the external molecular layer, is 0-064 mm., 

 whereas at the edge of the fovea it amounts to as much as 0-145 mm. 

 We are nnable to understand how it is that in Schwalbe's specimen 

 it should have been of the uniform thickness which is depicted in his 

 diagram. 



As to the vertical direction of the central fibres of this layer, 



