174 PATTEN. [Vou. Il. 
branches of medullary stalk; crown of ganglion cells; primary nerve 
fibres; optic ganglion of late larval stage; origin of the three lobes of 
imaginal ganglion from three segments of larval one é : + 137-144 
Optic NERVES. — Position; course . : : . . . . - 144-145 
NEURILEMMA. — Origin from basement membrane; structure . i . 145-146 
ORIGIN OF GANGLION CELLS. — Modified tripolar sensory cells; position and 
structure; passage from eye to optic ganglion; structure of outer prolon- 
gation; gigantic ganglion cells of larve; position near medullz; connect- 
ing fibres; small ganglion cells, probably tripolar; Vespa . - . 146-150 
COMPARATIVE ANATOMY OF OpTic GANGLION.— Optic ganglion of Vespa; 
of Astacus; Cymothoa; Cecropia; homology of optic ganglion of insects 
with that of Crustacea; the three lobes of optic ganglion of convex eye of 
Arthropods homologous with the three-segmented ganglion of the larvee, 150-154 
PART III.—SUMMARY AND COMPARISON. 
Large nucleus; horizontal rods; mosaic of upright and horizontal rods; struc- 
ture of horizontal rods supports the theory that retinidial fibrille are at 
right angles to the rays of light; eyes of Hydrophilus; comparison with 
Grenacher’s figure of larval eye of Dytiscus; eye of Chauliodes . 154-158 
Comparison of Myriapod eyes with those of Acilius . ; c . 158-161 
Eyes of Scorpions and SprpERS; absence of ganglionic saaatintion, in Arach- 
nids; possible explanation of inversion of retina in anterior eyes of 
Spiders. : ; : : : : : - 5 : - 161-166 
Convex Eye; origin; frontal ocelli ofimagines’ . ; : ; . 166-168 
NEUROEPITHEL CELLS . : : - : . : é 4 - 168-169 
SUMMARY : : : : - ; : : : : A - 169-173 
CONTENTS ; : - - : 2 , c - : - 173-174 
EXPLANATION OF PLATES : , : : : : ; : . 178-190 
