eye of stygicola. 223 



a larger eye, but in others it is considerably larger. The cartilage degenerates rap- 

 idly. In the eye of the mother of 125 a and b (92 mm.) only a few cells are left 

 (plate 26, fig. E, scl.c). 



This history of the scleral cartilage in Lucifuga and Stygicola is in distinct con- 

 trast to its history in Amblyopsis. In the latter it appears as the last of the eye 

 structures and remains after everything else has disappeared. The early history 

 in Lucifuga and Stygicola is not known, but it disappears even more rapidly than the 

 lens, only a few cells sometimes remaining longer. Aside from the cartilage the 

 sclera consists of a thin, fibrous, nucleated membrane over the proximal face of the 

 eye and a similar membrane, and the cornea over the distal face. The cornea may 

 remain for a long time after birth or it may, especially if the eye becomes compact, 

 disappear and be replaced by an accumulation of cells such as have been seen in 

 Amblyopsis and Lucifuga. With age the sclera becomes a fibrous capsule of varying 

 thickness (plate 26, figs. E and f). 



THE CHOROID AND THE ORBITAL PIGMENT. 



The choroid in the eyes of the young consists of a thin membrane containing 

 blood-vessels and pigment cells. Its structure can best be seen where it has acci- 

 dentally become removed from the pigment layer by reagents. The blood-vessels 

 may become so distended with blood that the thickness of this layer becomes several 

 times its normal thickness. Between the choroid and the sclera in the young is a 

 well-developed suprachoroidal lymph space. In contrast with Lucifuga, where 

 this space is largest between the choroid and scleral cartilage, it is usually thin or 

 absent in this region but comparatively well developed on the proximal face of the eye. 

 In the old it is not evident (plate 25, figs. E and r, chr. I.). As in Lucifuga there 

 appears, concomitant with the degeneration of the eye, an accumulation of pigment 

 in the orbital fat or in the choroid. The outlines of such a mass in contact with the 

 eye are shown in plate 26, figure F, representing the eye of a fish 135 mm. long. 

 The accumulations of pigment in both eyes are very large — larger than the eye. 



THE LENS. 



As in the eyes of Lucifuga, the lens degenerates and disappears more rapidly 

 than other parts. The methods of degeneration are seen in the lenses of 125 a 

 (plate 25, fig. h). The nuclei become distended, the chromatin accumulating in a 

 few nucleoli-like granules. The membranes of the nuclei next dissolve and there 

 results a mushy mass containing lumps of chromatin. The contents of the lens 

 capsules are next removed in a manner not clear. Toward the end of this process 

 the lens may be found to consist of a shrunken, fibrous membrane containing 

 pigment granules and accumulations of pigment — possibly cells. There is not a 

 vestige of the lens left in old individuals. 



THE IRIS. 



The iris in the young appears much darker from the surface than the rest of 

 the eye. In sections it is found to be not more densely pigmented than the pigment 

 layer. The epithelial part may be entirely pigmented, or the inner cells may be par- 

 tially free from pigment. At birth the pupil is larger than the lens and it remains 



