THE BLIND FISHES OF MAMMOTH CAVE. 29 
whole family of cods and their allies, to which group they belong, 
essentially marine. Further than this the cat fish from the subter- 
ranean stream in Pennsylvania belongs to a family having many 
marine and brackish water representatives. As another very in- 
teresting fact in favor of the theory that the Heteropygii were 
formerly of brackish water, we have the important discovery by 
Prof. Cope of the Lernzan parasite on a specimen of Amblyopsis 
from the Wyandotte cave; this genus of parasitic crustaceans be- 
ing very common on marine and migratory fishes, and much less 
abundant on fresh water species. 
Thus I think that we have as good reasons for the belief in 
the immutability and early origin of the species of the family of 
Heteropygii, as we have for their mutability and late development, 
and, to one of my, perhaps, too deeply rooted ideas, a far more 
satisfactory theory ; for, with our present knowledge, it is but the- 
ory on either side. 
4 EXPLANATION OF PLATES. 
PLATE 1. 
(All the fig rae Int t = | ing by Prof. J. Wyman.} 
Freé.1. Brain, nerves and organ of hearing of Amblyopsis speleus; enlarged; a, E 
tory lobes and nerves; b, cerebral lobe D e bes; d, cerebel 
organ of hearing, showing the semicircular canals, with the otolite repre- 
sented in place by the dotted lines; f, mrin oblongata; g, optic nerves 
tural ixteenth of an inch in Smeal a, optic pyd 
"8, solaroiio i c, layer of colorless cells; d, layer of Pen 
(iris ?); e, 1 
Fie. 4. Lens, laii and bA e the cells. 
Fig. 5. eo ee g the muscular bands, a, a, a, a; b, the lens pressed out 
lace; ¢, ney Sons nerve. 
Fie. 6. Top of ‘head, showing the canals under the — of the natural size. The two 
Fig.7. Top of head, showing the arrangement of the ridges of papillæ. Natural size. — 
FIG. 8. One of the ridges of papillz from the head, magni 
Fig. 9. hand of the papille from the ridge, still more sumepniied, showing the cup- 
summit and projecting filament. 
Fig. 10. A portion of the ridge i nd treated with acid, to show the arrange- 
branch (a) of the fifth pair. _ 
A fish with eyes, found: in the ‘stomach of an Amblyopsis. 
