STUDIES IN THE RETINA. 71 



EXPLANATION OF PLATES 3—5, 



Illustrating Parts III, IV, and V of Mr. H. M. Beruard's 

 paper on " Studies in the Retina/' 



N.B. — TLe measurements of the different eyes can only be approximate, 

 because the shape is not always kept in very thin sections. It should be 

 further noticed that sometimes a slightly older eye may be smaller than one 

 obviously younger, a fact to be attributed to the accidents of nutrition. 



In all the figures ni.l. = limiting membrane,^./. = "ganglionic cell" 

 layer, i.r. = inner reticular layer, t/ui. = middle nuclear layer, o.r. = outer 

 reticular layer, o.n. = outer nuclear layer. 



Fig. 1. — Frog ladiwle (Perenyi's fluid). Eye diameter 0-32 mm. Part 

 of section showing tlie spindle-shaped nuclei of the undifferentiated rim of 

 the retina, attached to either the inner or the outer limiting membrane, and 

 arranged on the axial side in curves bulging towards the axis of the eye. 

 The arrow indicates the direction of the nuclear stream. A few of the 

 nuclei already in the middle layer, selected because attached by trailing cyto- 

 plasm to the inner reticular layer. 



Fig. 2. — Toad tadpole (Lindsay-Johnson's fluid). Eye diameter 0-528 mm. 

 Part of section drawn with the camera lucida, to show the attachment of the 

 inner reticular layer to the menibrana limitans interna, this connection being 

 apparently due to the nuclei trailing their cytoplasmic attachments behind 

 them as they travel towards the axis of the eye. These nuclear attachments 

 tend to accumulate on each side of the stream, but persist as an accumulation 

 only on the inner side (see text, pp. 10 — 13). 



Fig. 3. — Frog tadpole (picro-sulphuric and iron hsematoxylin). Eye dia- 

 meter 0-24 mm., to show a younger stage in the formation of the inner 

 reticular layer. The nuclei, which in the central region are loosely arranged 

 where this layer is beginning to form, are densely crowded, five to six deep, against 

 the pigment, and are apparently pressing inwards from the undifferentiated 

 rim where nuclear divisions (/t.) are taking place. The arrows indicate the 

 direction of the streaming; o.r. indicates aline of dark staining matter where 

 the future outer reticular layer will run. 



I'iG. 4. — From the other eye of the same animal. In both these eyes yellow 

 fluid was apparent in the pigment cells, and here and there also apparently iu 

 vesicles which appear among the pigment granules, and were probably pro- 

 truded from the retina (cf. Fig. 18). 



