THE 
BULLETIN OF 
fully later on. It is not my purpose to give an account of the general 
structure of the fish in this paper. I must, however, call attention to 
the far reaching modifications that have been brought about by its 
peculiar habits, not in the eyes merely, but in many other structures, 
As already mentioned, Dr. Eigenmann has shown that the “ entire 
frontal region of the skull has been profoundly changed.” He has also 
shown that the fins of the adult are much thicker, more fleshy, and 
shorter, in proportion to the size of the body, than in the young. My 
observations fully confirm these statements. 
In the smallest specimens that I have seen, 19 mm. long, the eyes 
are distinctly visible without dissection. In some of the preserved 
specimens of this and somewhat larger size, the lens is also clearly seen 
in surface views ; while in other specimens it is not so distinct, and in 
some is scarcely seen at all, though it is probably always present in all 
these younger individuals. 
The eyes are situated wholly on the dorsal aspect of the head, and 
very near together (Plate I. Figs. 1, 2). Their distance backward from 
the tip of the nose is also short as compared with the length of the 
fish. Thus in the specimens 19 mm. long this distance was 0.95 mm., 
or one twentieth of the entire length of the fish. In large individuals, 
especially while living, the eyes are visible from the surface, but appear 
as scarcely more than black specks deeply buried in the tissue. In 
many cases they cannot be seen at all in preserved specimens. 
The epidermis immediately over the eyes does not differ essentially, 
either in the smaller or the larger individuals, from what will be de- 
scribed further on as existing in other portions of the dorsum and sides 
of the head and body. The mucous cells are present here as else- 
where, and they are as numerous and as large as in adjacent regions. 
The average thickness of the epidermis is 50 y in the smallest specimens 
studied ; 63 in a specimen 60 mm. long, and 76 p in a specimen about 
65 mm. long, thus showing a gradual increase in thickness with the 
increasing size of the animals. In the smallest specimens the sub-epi- 
dermal tissue over the eye is not differentiated into a dermal and sub- 
dermal layer. The connective tissue in this region is arranged in several 
strands which unite with one another at various angles, thus bounding 
wide spaces (Plate III. Fig. 17, spa.). In this specimen (Fig. 17) the 
space between the epidermis and the sub-epidermal tissue is quite wide, 
and is continuous over the entire eye, and for a considerable distance 
beyond. This space may be in part artificial ; but even if so, the con- 
nection between the epidermis and the immediately underlying tissue 
