STUDIES IN THE RETINA. 35 



layer to the internal membrane were the remains of the 

 attachments of the originally spindle-shaped nuclei which 

 had moved away down the middle nuclear layer. 



More conclusive still is the fact that every now and then 

 a section is found in which the nuclei of the middle layer, 

 especially near the rim, are actually caught trailing irregular 

 tangles of cytoplasmic threads in the manner shown in figs. 1 

 and 2. This can be seen with some frequency, though by 

 no means always, because it is probably a matter of accident 

 whether the particular retina happened, at the moment 

 it was fixed, to be in the exact phase of its life activities 

 which required such movements. For it is hardly likely that 

 the inward streamings of nuclei are continuous ; periods of 

 rest would probably intervene. However seldom they occur 

 there is no mistaking their significance. 



Still keeping the movement of the nuclei in view, it is 

 worth while paying further attention to the inner reticular 

 layer. We find that the early stages in its appearance 

 show differences which, though at first disconcerting, are yet 

 on the whole entirely confirmatory. The earliest stages which 

 I have so far seen are shown infigs.5, 6,and 7, which linterpret 

 as follows : — The nuclei, which had been fairly evenly dis- 

 tributed through the retina, and not tightly squeezed together 

 (see fig. 7), gradually separate along the line which will be 

 later occupied by the inner reticular layer, the larger half 

 migrating outwards. A row, two or three deep, remains 

 against the internal limiting membrane, although one or two 

 even of these, in the axis of the eye, may escape outwards, 

 leaving a gap in the innermost layer (figs. 5 and 6). Thegi-ent 

 mass of the nuclei gradually move, as stated, outwards, but the 

 very outermost can at the most move but a few micromilli- 

 raetres, being arrested at once by the pigment epithelium. 

 The rest, therefore, leaving a few stragglers, crowd up close 

 behind, with the result that the irregular but conspicuous rent, 

 just described, occurs in the previously uniform nuclear ranks. 

 This rent in its early stages seems to be mainly occupied by 

 rounded vesicles, at least in the retina from which fiL>-. 7 Avas 



