‘ 
318 THE CEPHALOPODA 
head and are generally sessile. They are, however, pedunculated 
in many embryos (Fig. 290, (8), (9)) and in the adult Taonius (Fig. 
253, e) and other Cranchiidae, and also in some Amphitretus (Octopod). 
The eye of Nautilus (Fig. 293, e) is an open vesicle with a minute 
aperture (Fig. 6, A): it is devoid of any kind of refractive apparatus, 
and its internal retinal wall is pigmented throughout. In the 
Dibranchia the cavity of the eye is closed, as it is in the majority 
of Gastropoda, and the ocular globe consists of the same essential 
il 
Jo 
o} 
Fic. 283. 
Horizontal section of the eye of Sepia. ae, argentine integument; C, external cornea ; ci, 
” 
ciliary body; g.o, optic ganglion; 7k, cartilage of the “iris”; k, k’, capsular cartilage; KK, 
cephalic cartilage; L, lens; 0, optic nerve; P, retinal pigment; Ke, Wi, external and internal 
layer of the retina; w, white body. (From Lankester, after Hensen.) 
parts, viz. retina, cornea, and crystalline lens, with various accessory 
parts added, making it a very complex and perfect organ of vision. 
The ocular globe is applied to the cephalic cartilage, is sometimes 
contained in a more or less incomplete orbit formed by a wing- 
shaped expansion of the cartilage (Sepia), and is provided with a very 
large optic ganglion (Fig. 283, g.o). In the Dibranchia the retina 
occupies the inner part of the ocular cavity, and the rods are turned 
towards the light. The cornea is situated between the two segments 
of the cuticular body forming the crystalline lens (Fig. 283, L): 
above the more superficial and smaller segment of the lens a fold of 
the integument forms a contractile iris, with a circular (Oigopsida) 
