F. S. CONANT ON THE CUBOMEDUS^E. 53 



to which they belong I can say nothing except that from such evidence 

 as I have given in the preceding paragraph I conclude that they come 

 from pigmented retinal cells of not very different type within the retina 

 from the others, if different at all. 



(c) On the third point, that the pigment streaks in the vitreous 

 body belong to underlying cells and are continued distally into fibrous 

 processes like the visual fibres of Schewiakoff, the evidence is decisive. 

 Fig. 58 has already shown it, and if this were not enough, a case of 

 unusual stoutness of the fibres drawn in Fig. 67 is conclusive. The 

 preparation from which the section is taken was one preserved with 

 corrosive-acetic, and I have drawn the outlines with the camera in order 

 to avoid exaggeration of the fibres as far as possible, and also to show 

 the shrinkage of the vitreous body (vb). It is the shrinkage of the 

 vitreous body that makes it so difficult to determine the exact relation of 

 structures seen in the vitreous body to the retina. The fibrous processes 

 run through the vitreous body to the "capsule" of the lens (cp) (see 

 also Fig. 72), a layer of homogeneous substance much resembling that of 

 the vitreous body, which is classed as a part of the vitreous body, but 

 usually in the shrinking adheres to the lens. The capsule is therefore 

 regarded by Schewiakoff as a secretion of the lens cells. Some fibres 

 were found by him to have the appearance of branching upon reaching 

 the surface of the capsule, others of passing through it and of seemingly 

 ending among the cells of the lens. The same appearances were given 

 in my sections. It is altogether impossible in the distal portion of the 

 vitreous body to distinguish between the fibres of Schewiakoff and those 

 that come from the long pigment cells. (Figs. 64-66 represent the 

 appearance of the vitreous body at successive levels, and are from the 

 same series of sections as Figs. 59-62 and 72.) In Fig. 64 the sections of 

 the processes that Schewiakoff calls visual are easily distinguished from 

 the sections of the long pigment cells. In Fig. 65, which is two or three 

 sections nearer the lens, the pigment cells are shown by their cross- 

 sections to be tapering down, and in Fig. 66. nearer still to the lens, the 

 two kinds of processes are no longer to be distinguished from each other. 

 In a few cases I have found pigment in a fibre which but for this would 

 be called one of the visual fibres of Schewiakoff. Such considerations as 

 these, the similar appearance in cross-section, the finding of pigment in 

 a few cases, and the inability to trace to any readily distinguished special 

 type of retinal cell, make me wonder whether the visual fibres of 

 Schewiakoff are anything more than the distal processes of pigment 



