82 



Looking 1 into the pupil the lens can be seen. This is 

 a spherical ball, built up of concentric layers of a non- 

 cellular, transparent, cuticular, crystalline substance (fig. 

 78, L). Looking- down into the pupil the eye appears 

 black, because the dark retina shows through the lens, 

 from behind. 



Fig. V. Eye of E. cirrosa, showing various stages of dilatation of 

 pupil, x 2. 



The eye is enclosed in a cartilaginous cup, that 

 adheres internally to the " skull.'' This cup is thickest 

 at the base hut much thinner at its external edge, which 

 reaches about half-way round the eye (fig. 85 a, orb. C). 

 External to the capsule a strong muscular coat is attached 

 which surrounds the eye and extends as far as the lid 

 (tig. 78, Ext. Muse). Internal to the capsule is a second 

 muscular coat, which extends to the border of the pupil, 

 and is more delicate than the first (fig. 78, Int. Muse). 

 The retina, sclerotic, &c., form a roundish, rather 

 depressed chamber that only occupies about one-third of 

 the whole volume of the eye. Behind this chamber is a 

 second much larger one that contains the optic ganglion, 

 which gives off from its external surface a great number 

 of nervous strands to the retina, and the white body 

 (fig. 78, Opt. G. and W. B..). 



The white body is a glandular mass surrounding the 

 optic ganglion, and consists of three lobes — one large 

 dorsal and two smaller ventral (Text tig. VI). This 

 body has been shown to be the remains of a 

 degenerate portion of the embryonic nervous system, 



