THE EVE OF CRVPTOBRANCHUS. 2$ 



be seen inside of this ganglion-cell layer, nor can the connection 

 of the optic nerve (Op] with the retina be determined. The 

 ganglion-cell layer lies, as a rule, in close contact with the lens, 

 so that there is no vitreous cavity ; the narrow space that sometimes 

 appears between the inner layer of the retina and the capsule of 

 the lens is probably due to a slight distortion of the eye. 



One of the most striking features of this eye is the large sur- 

 face covered by the retina ; it extends as is partially shown on 

 the right side of the figure, for some distance in front of the region 

 of the ciliary process, if the thickening of the choroid may be so 

 called. Another striking feature of the retina is the marked fold 

 seen in the region of the ciliary thickening. All of the retinal 

 layers take part in this fold (F), which varies somewhat in com- 

 plexity in different eyes, but is evidently a normal condition and 

 not a mere artifact. 



The lens (Z) presents no striking peculiarities ; it is almost 

 spherical in form, and completely fills the cup of the eye, so that 

 the vitreous cavity, as has been said, is obliterated ; a small 

 space between the front of the lens and the cornea (at the end of 

 the reference line P) may, perhaps, be taken to represent the 

 aqueous cavity. The lens is surrounded by a comparatively 

 thick capsule (Lc), whose distinctness is somewhat exaggerated 

 in the figure. 



The correlation of some of the above-described structures with 

 the habits and mode of life of the giant salamander is not diffi- 

 cult to determine, but in other cases the correlation is not so 

 certain. 



The flattened anterior surface of the bulb, for example, is seen 

 in most aquatic amphibia and may be merely a measure of pro- 

 tection against injury by coming in contact with the rocks and 

 other objects under which the animal may hide ; again a flat- 

 tened or depressed cornea would evidently offer less friction in 



swimming. 



A cartilaginous sclerotic is common among the amphibia, but 

 it is difficult to see the necessity of such a heavily chondrified 

 sclerotic in an eye that is so deeply buried as is this one. The 

 spherical lens resembles the same structure in the teleosts, and 

 probably indicates that the eye is especially adapted to vision at 



