184 PATTEN. [VoL. II. 
EXPLANATION OF PLATE X. 
Fics. 42-47. A series of sections through the head of an embryo just after the 
rupture of the embryonic membranes. See Fig. 8. They show the structure of the 
brain and its envelop, optic ganglion and eyes, as well as the tracheal invagina- 
tions of the head. For explanation of last-named structures, see my next paper on 
the “ Development of Acilius.” Ka383 
Fic. 48. Horizontal section of the optic ganglion, from an embryo just ready to 
hatch. The break in the outer neurilemma is on the side next the eyes. It is im- 
portant to notice the remarkable similarity between the structure of the medulle and 
the retinas to which they belong. 
Fics. 49, 50. Two vertical sections through the optic ganglion of a full-grown 
larva; showing the medullz and nerves, and the three lobes of the ganglion. X 170. 
Fics. 51-53. Three horizontal sections of the optic ganglion of a full-grown 
larva. Shows same as preceding sections. X 170. 
Fic. 54a. Cross section of the rods in the fifth Eye; showing axial nerves, retini- 
dia, etc. 
Fic. 544. Same from the sixth eye; showing loops of axial nerves, etc. 
Fic. 55. A vertical section through the furrow of eye I.; showing the ends of the 
giant, and small rods. Compare Fig. 56. 
Fic. 56. Vertical section of the horizontal retina of the first eye; showing the 
double row of giant cells with their external nerve fibres, the layer of vertical fibres, 
with their fibrillee, and the ends of the small horizontal cells, etc. 
Fic. 57a. Semi-diagrammatic view of a retinal cell from the fifth eye; showing the 
double retinophorze, and the position and shape of the rods belonging to each cell of 
the retinophora, etc. 
Fic. 574. Same, in side view. 
Fic. 58. Retinophorz isolated by maceration. 
a. A double cell, decolorized, from the fifth eye. 
4, Isolated cell from the sixth eye. The primary and secondary nuclei are 
situated close together. 
c. Two double cells, depigmented, from the sixth eye; showing the nerve 
fibres and the deceptive shape of the inner ends of the retinal cells. 
d, Same. 
e.f. Two views of a small retinal cell with horizontal rods, probably from the 
second or fourth eye. 
g. Decolorized retinophora that showed especially well the shape of its com- 
ponent cells. 
A. A fragment of a retinal cell with a tripolar ganglionic cell attached to it. 
z. Two giant cells from the first eye; showing how the light and dark cells 
overlap. 
Fic. 59. Horizontal section of the first eye; showing one of the rows of giant 
cells and the two layers of vertical fibres with the medulla-like substance between. 
Compare Fig. 56. 
Fic, 60. Horizontal section of the row of small retinal cells just above the giant 
cells in the horizontal retina of the first eye. It shows how the rods of each retino- 
phora unite with each other above the centre of the cells, and not with the rods of 
neighboring cells, as in all other cases. See Fig. 57a. 
