56 BULLETIN OF THE 



fully later on. It is not ray 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 thickei', 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 numeroua and as large as in adjacent regions. 

 The average thickness of the epidermis is 50 /x in the smallest specimens 

 studied ; G3/i, in a specimen 60 mm. long, and 76 /x. 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 diff'erentiated 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 



