No. t.] EVES OF ARTHROPODS. 173 
CONTENTS: 
Introduction . 5 : : - : : ; : 4 7 : Oy, 
Topographical relation of optic plate and ganglion to cephalic lobes and brain, 97 
PART I.—EYES. 
EYE V. 
Position; explanation of surface views; sense organs; optic cup; optic vesi- 
cles; cuticular thickenings; median ridge; median furrow; comparison 
of sensory pits with eyes on mantle of Molluscs; corneal and retini- 
dial cuticula; the eye composed of a collection of sensory spots; large 
nucleus; closure of optic cup, and formation of the three layers; cor- 
neagen; iris; pigment; cuticular pellicle; lens; the retina; second me- 
dian ridge; double row of cells with horizontal ends; retinophore; 
pigment; retinal rods and nerve endings; rods in Cephalopods; in Arca, 
etc.; nerve bundles . : E 3 ; : ; : 5 : Q9Q-I12 
EYE VI. 
Position; surface views; sensory pits; closure of optic cup; sixth sensory 
spot forms tongue of inverted cells; corneagen retina; rods . - 12-115 
EYE III. 
Position; surface views . : ; : : 6 : ° - - II5-116 
: EYE I. 
Position; surface views; contain two large nuclei and nine sensory pits; invag- 
ination of eyes I. and III.; corneagen; retina; retinophorz; nerve ends; 
rods; dorsal appendage . - . é ; : : < . 116-129 
EYES II. AND IV. 
Position; invagination; retina; shape; lens; asymmetry 5 : . 129-131 
PART II.—OPTIC GANGLION. 
ORIGIN OF OpTIC GANGLION. — Topography; three segments; invagination of 
first two segments and inward proliferation of the third; connection of 
inner surface of optic plate with the segments of: the optic ganglion; 
proliferation of ganglion cells; theory of invagination of optic ganglion; 
inclosing of ganglionic segments by growth of optic plate; optic ganglion 
before rupture of embryonic membranes. : : : : - 131-137 
MEDULL& OF OpTic GANGLION.— Position; shape; structure; structure is 
similar to that of retina to which it belongs; signification of this similarity; 
