164 ANIMAL FORMS 
the touch. The herring and shad are examples, as also the 
salmon and trout. Some live in the great depths of the 
sea, even five miles below the surface. These are very soft 
in body, being under tremendous pressure. They are inky 
black—for the sea at that depth seems black as ink—and 
most of them have luminous spots which give them light 
in the darkness. Some species have the forehead luminous, 
like the headlight of an engine. Most of these deep-sea 
fishes are very voracious, for there is nothing for them to 
feed on save their neighbors. 
160. The pike, sticklebacks, ete.—Several small orders 
stand between these soft-rayed, smooth-scaled fishes and 
¥1e. 102.—The blindfish and its parentage. A, Dismal Swamp fish (Chologaster 
avelus), the ancestor of (B) Agassiz's cave fish. (Chologaster agassizi) and (C) 
cave blindfish (7yphlichthys subterraneus). 
the form, like the perch and bass, which has many spines in 
the dorsal fin. Among these transitional forms is the pike 
(Fig. 103)—long, slender, circumspect, and voracious, lying 
in wait under a lily-pad; the blindfish, which lost its eyes 
through long living in the streams of the great caves; the 
stickleback, small, wiry, malicious, and destructive, steal- 
ing the eggs and nibbling the fins of any larger fish; the 
sea-horse, clinging with its tail head downward to floating 
