The Grayling and the Smelt 1 3 1 



oceanic depths. The "Bombay duck" of the fishermen of 

 India is a species of Harpodon, H. nehereus, with large mouth 

 and arrow-shaped teeth. The dried fish is used as a relish. 



The Benthosaurida are deep-sea fishes of similar type, but 

 with distinct maxillaries. The Bathypteroida, of the deep seas, 

 resemble Aulopus, but have the upper and lower pectoral rays 

 filiform, developed as organs of touch in the depths in which 

 the small eyes become practically useless. 



Ipnopidae. In the Ipnopidce the head is depressed above 

 and the two eyes are flattened and widened so as to occupy 

 most of its upper surface. These structures were at first sup- 

 posed to be luminous organs, but Professor Moseley has shown 

 them to be eyes. "They show a flattened cornea extending 

 along the median line of the snout, with a large retina com- 

 posed of peculiar rods which form a complicated apparatus 



FIG. 90. Ipnops murrayi Giinther. 



destined undoubtedly to produce an image and to receive 

 especial luminous rays." The single species, Ipnops murrayi, 

 is black in color and found at the depth of 2^ miles in various 

 seas. 



The existence of well-developed eyes among fishes des- 

 tined to live in the dark abysses of the ocean seems at first con- 

 tradictory, but we must remember that these singular forms 

 are descendants of immigrants from the shore and from the 

 surface. " In some cases the eyes have not been specially 

 modified, but in others there have been modifications of a lumi- 

 nous mucous membrane leading on the one hand to phosphor- 

 escent organs more or less specialized, or on the other to such 

 remarkable structures as the eyes of Ipnops, intermediate 

 between true eyes and phosphorescent plates. In fishes which 

 cannot see, and which retain for their guidance only the general 

 sensibility of the integuments and the lateral line, these parts 

 soon acquire a very great delicacy. The same is the case with 



