RETINA OF LATERAL EYES OF SPHENODON PUNCTATUS. 327 
shown and the several layers of the retina. The pigment is separated 
from the other layers except at the macula lutea. The central fovea is 
cut a little to one side. From an eye fixed by acetic bichromate and 
stained with Ehrlich’s liaematoxylin . X 20. 
Fig. 2. — Vertical section through a portion of the choroid and of 
the retina, showing the arrangement of the various layers of the retina 
at the fovea centralis and the surrounding macula lutea. From an eye 
fixed with acetic bichromate and stained in bulk with borax carmine, 
and on the slide with picro-indigo-carmine. X 160. 
Fig 3. — Tangential section through part of the retina, showing the 
pigment epithelial layer and the layer of cones cut at various levels. 
Acetic bichromate material, stained heavily with picro-indigo-carmine. 
X 560. 
PLATE 28. 
[All the figures are from drawings of preparations of the retina of 
Sphenodon punctatus. They have been outlined in every case by 
camera lucida.] 
Fig. 4. — Portion of a vertical section, half way between the macula 
lutea and ora serrata, to give a general view of the arrangement of the 
various layers of the retina. The preparation was from material fixed 
with Fleming’s solution, stained in bulk with borax carmine and on the 
slide with brazilin. x 440. 
Fig. 5. — Vertical section through the layer of cones, showing nine 
cones, six of which are ordinary single ones, three double. Of two of 
the latter, however, only the near cone is in focus. The preparation is 
from material preserved in Zenker’s fluid, stained in bulk with borax 
carmine and on the slide with picro-nigrosine. X 1120. 
Fig. 6. — Two ordinary single cones to show the structure of the 
outer segments. The outer segment of (a) is broken up into transverse 
discs, while that of ( b ) shows the spiral twisting sometimes seen in the 
inner half of the outer segment. The preparation is from material 
preserved in Flemming, and stained with an attempt at the Weigert 
Pal method (see “ Methods,” p. 308). x 1120. 
Fig. 7. — One ordinary single and one double cone to- show their 
general structure and the arrangement of their nuclei and fibrils in the 
outer nuclear layer. The outer segments have been broken away in 
the course of preparation. Staining as for fig. 6. x 1120. 
Fig. 8. — Portion of layer of cone-cells to show position and structure 
of two small single cones, (c) and ( d ), and their nuclei in relation to the 
ordinary single and double cones. No outer segments are shown. 
Staining as for fig. 6. x 1120. 
