362 H. M. BERNARD. 



the rim of the retina, c being nearest to tlie centre, sliowin;^ rod-vesicles beinj^ 

 protruded from tlie distal ends of the radial attachments of the spindle-shaped 

 cells which persist at the rim of the retina. On the extreme right in a two 

 nuclei are seen connected together, and in b two vesicular protrusions from 

 nuclei are seen, and into them radiating strands come from the nuclei. 



Fig. 24. — A diagram representing what I conceive to be the change which 

 converts the columnar epithelium of the pars ciliaris retina; into a thick 

 layer of closely packed spindle-shaped cells, this layer being later broken up 

 into the normal zones of the retina by the wandering inwards towards the axis 

 of the nuclei of these cells. Tiie protrusion of fluid-vesicles beyond the 

 membrana limitans externa is already foreshadowed by a distal accu- 

 mulation of fluid in the otherwise iindiff'erentiated cells of the columnar epi- 

 thelium, which may be occasionally seen. 



Fig. 25. — Part of a radial section through the retina of a young cat, two 

 days old (L'errenyi's fluid), to show the proximal nuclei nearly all devoid of 

 chromatin, which is massed in the distal or rod-nuclei. The inner or ganglionic 

 layer is of enormous thickness and full of small vesicular nuclei, many appa- 

 rently fragmenting. Fig. 20 a is from the same eye. 



Fig. 2G. — A small selection of retinal ganglionic cells to show how, at 

 times, the nucleus and its granular cytoplasm may have nearly the same 

 shapes, a—f, from old cat (Flemming) ; ff, young cat, six weeks (Perrenyi); 

 h — q, young dog (Flemming). They illustrate also the arrangement of the 

 *' Nissl's Schollen " which may at times form a series concentric with a series 

 of chromatin clumps within the nucleus (see y). 



Fig. 27. — Extra-nuclear networks (see p. 351). a, h, c, e. From the retina 

 of a mouse tired out by exposure to an arc lamp (Perrenyi) ; d, of a rat, 

 young adult (Flemming); «, b, c, e, a group of "ganglionic" nuclei; on the 

 right in a, the same network is common to two nuclei. Very similar pheno- 

 mena were also seen in a wild mouse fixed in corrosive sublimate, only the 

 networks were not quite so sliarjily defined, c. From the same, shows a large 

 ganglionic nucleus with two extra-nuclear networks ; that on the right seems 

 to have dissolved the wall. e. From the same, showing a nucleus wiih the 

 wall all round apparently dissolved, d. From a rat, young adult (Flemming), 

 showing a nucleus of the middle layer passing through the outer reticular 

 layer with an extra-nuclear network preceding it (cf. fi:;s. 20 and 27 of Part II). 

 Two stellated nuclei of the rod-layer arc also shown (cf. Figs. 20 c, d, e). 



Fig. 28. — From the retina of a Proloptcrus (Flemming), showing two nuclei 

 passing with amceboid movements through the outer reticular layer to become 

 rod-nuclei. The rod-nuclei protrude a long way through the m. I. e. 



