BRANCH CHORD AT 4; CLASS PISCES: THE FISHES 287 



Some have bony coats of mail and sometimes the coat of 

 mail is covered with thorns, as in the porcupine-fish. 

 This fish and various of its relatives have the habit of filling 

 the stomach with air when disturbed, then floating belly 

 upward, the thorny back only within reach of its enemies. 

 Many species (cling fishes) attach themselves to the 

 rocks by a fleshy sucking-disk. Some (Remora) (fig. 1 1 8) 

 cling to larger fishes by a strange sucking-disk on the head, 

 a transformed dorsal fin, being thus shielded from the 



FIG. 118. The remora, or cling fish, Remoropsis brachyptera. Note sucker 

 on top of head. (After Goode.) 



attacks of fish smaller than their protectors. Some small 

 fishes seek the shelter of the floating jellyfishes, lurking 

 among their poisoned tentacles. Others creep into the 

 masses of floating gulf-weed. Some creep into the shell 

 of clams and snails. In the open channel of a sponge, 

 the mouth of a tunicate and in similar cavities of various 

 animals, little fishes may be found. A few fishes (hag- 

 fishes) are parasitic on others, boring their way into the 

 body and devouring the muscles with their rasp-like 

 teeth. 



Some fishes are provided with peculiar modifications of 

 the gills which enable them to breathe for a time out of 

 water. Such fish have the pectoral fins modified for a 

 rather poor kind of locomotion on land, thus enabling 

 them to move from pond to pond or from stream to stream. 

 In cold climates the fishes must either migrate to warmer 

 latitudes in winter, as some do, or withstand variously the 

 cold, often freezing weather. Some fish can be frozen 



