THE BLIND TYPHLOGOBIUS OF CALIFORNIA. 67 



the base of Point Loma, where the waves sometimes dash with great force, the 

 blind fish is its associate. 



On rough days few fishes are seen, though ever so many stones are overturned. 

 On mild days, on the contrary, at very low tides quantities are found almost invari- 

 ably in company with one of the crustaceans mentioned above. Sometimes the 

 fishes live quite out of water on the damp gravel and sand under a rock, but more 

 frequently small pools of water fill all the depressions under the rocks, and the 

 fishes swim rapidly away to hide in the crab holes, several of which always branch 

 from the cavity in which the rock has lain. Very rarely are the fishes found 

 swimming in rocky tide pools. 



In the bay the gobies habitually live outside of the holes, descending into them 

 only when frightened ; but at Point Loma they rarely leave their subterranean 

 abodes, and to this fact we must attribute their present condition. How long 

 these fishes have lived after their present fashion it would be hard to conjecture. 

 The period which would produce such decided structural changes can not be a 

 brief one. The scales have entirely disappeared, the color has been reduced, the 

 spinous dorsal has been greatly reduced, the eyes have become stunted, and the 

 whole frontal region of the skull and the optic nerves have been profoundly changed. 



The skin, especially that of the head, has become highly sensitized. The skin 

 of the snout is variously folded and puckered. The nares are situated at the end 

 of a fleshy protuberance which projects well forward, just over the mouth. At 

 the chin are various short tentacles, and a row of papilke (which probably bear 

 sensory hairs) extends along each ramus of the lower jaw and along the margin 

 of the lower limb of the preopercle. The eye is, however, the part most seriously 

 affected. It is quite evident and apparently functional in the young (fig. 26 b). 

 Objects thrust in front of the fish are always perceived, but the field of vision is 

 quite limited. With age the skin over the eyes thickens and they are scarcely 

 evident externally. As far as I could determine they do not see at this time, and 

 certainly detect their food chiefly, if not altogether, by the sense of touch. A 

 hungry individual will swim over meats, a fish, or a mussel, etc., intended for its 

 food without perceiving it by sight or smell, but as it comes in contact with any 

 part of the skin, especially that of the head region, the sluggish movements are 

 instantaneously transformed, and a stroke of the fins brings the mouth immediately 

 in position for operations. 



Ritter's experiments showed that it would not choose between light and dark, 

 but, "On the whole, both from these observations on the living fish, and from the 

 structural conditions, ... I am of the opinion that the power of perceiving 

 light is not wholly lost even in the adult." 



The optic nerve is very slender and the lens proportionately very large. 



In the youngest individual caught (fig. 26 b), the membranes of the fins were 

 thin, the color cells well formed and arranged not unlike those of the young Gil- 

 lichthys. The movements were similar to those of the other gobies, and not at 

 all sluggish like those of the adult. Their favorite position is standing or sitting 

 with the broad pectorals extending out at right angles to the body. In this posi- 

 tion the fish can, with a sudden stroke of its pectorals, move quickly and rapidly. 

 In the old fish the fins are thick and smaller in proportion, and all the vivacity 

 seems to have disappeared. The color has degenerated, or at least not developed 

 in proportion to the growth of the fish. 



