EYE OF LUCIFUGA. 215 



more pigment in a more elongate mass. In the youngest individual (38 mm.) 

 with whose eyes pigment was found associated, it is close to the optic nerve on one 

 side of the body and along a fibrous strand on the other. 



The cells are fully charged with pigment, and no cells could be found with but 

 a few granules. In the next largest (43 mm.) there is a large pigment cushion on 

 the posterior face of the left eye. There are also a few fully pigmented cells scat- 

 tered distad from the eye. 



In individuals 44 mm. and 54 mm. long the pigment is also associated directly 

 with the eye, but the parts can not be readily distinguished. 



In an individual 53 mm. long there is a mass distad from the right eye over the 

 pupil, and another proximal to the left eye. These are the beginning of the masses 

 seen near the eye in older individuals. 



In an individual 57 mm. long there are small masses of pigment cells some 

 distance removed from the eye. On the left side the mass exceeds the size of the eye. 



In the left eye of an individual 63 mm. long there is a large amount of pigment 

 immediately around the eye and also masses removed some distance from the eye. 

 The same is true of the right eye, which is large and vesicular. 



In an individual 65 mm. long there is a small pigment mass remote from the 

 eye and a larger amount directly associated with it. 



In an individual 69 mm. long (plate 22, fig. a) there are masses of pigment 

 near the eye which is vesicular. In an individual 80 mm. long small masses are 

 found near the eye and there is much pigment in the eye. 



In the right eye of an individual 84 mm. long there is a very thick (30 /a) mass 

 of quadrate pigment cells in the choroid along the lower surface of the eye. The 

 pigment layer of the retina is but 4 /u. thick and there is a lenticular mass of pigment 

 cells, 46 x 34 /x in section, in the pupil. The vitreous cavity is obliterated. 



In one of the largest fishes, 93 mm., there are large masses near the eye as well 

 as a cushion of pigment affixed to the eye (plate 22, fig. b, pi. s.). 



From the above it is seen that the pigment masses make their appearance at 

 about the time the eye begins to actively degenerate, a short time after birth, and 

 that they reach their maximum development when the eye has reached the vanish- 

 ing point. The masses are first seen in a fish 38 mm. long in association with the 

 optic nerve and the muscles near the eye. In slightly older individuals the pig- 

 ment masses appear as lenticular cushions applied to the sclera, and in still older, 

 when the fish has reached 50 mm., other masses are seen more or less remote 

 from the eye, although pigment cushions may still be seen in some of the larger 

 specimens. In the very largest there are several masses in the neighborhood of the 

 eye or where it has disappeared. 



While it is practically impossible to make out the structure of the pigment 

 masses in their most intense development, it is evident that they are made up of 

 rounded bodies densely pigmented, several of which are bound by fibrous tissues 

 into subsidiary masses many of which together form the larger masses described. 



No doubt the smaller rounded bodies are cells. In their most intensely pig- 

 mented condition it is impossible to demonstrate this. In certain favorable cases 

 the individual pigment granules can be made out, as well as their arrangement in 

 the cell. In the very largest individuals some cells were found that contained but 

 one or very few pigment granules. 



