FISHES 133 



limbs of a terrestrial vertebrate) to clamber about over the rocks. 

 Not a few shore fish do this, and if a storm throws up upon the 

 beach a specimen of the curious fishing-frog or angler, it will 

 be noted that in that interesting fish the pectoral fins are almost 

 leglike in function, being used to enable the fish to " walk " over 

 the bottom, though they retain the structure peculiar to fins, 

 as contrasted with the terrestrial type of limbs bearing fingers 

 and toes. 



In captivity the shanny should be given an opportunity of 

 climbing partially out of the water : it will be found also to thrive 

 much better in shallow pans than in a relatively deep aquarium. 



Related to the shanny is the Butter-fish or Gunnel (Centro- 

 notus gunnellus), interesting because of its peculiar shape, but 

 not so attractive an occupant of the aquarium as the shanny. 

 Unlike the shanny, which has no scales, the butter-fish has very 



FlG. 63. Gunnel or butterfish (Centronotus gunnellus). (After Day.) 



small ones. Its body is peculiarly slimy, and, being compressed 

 and long, not only enables the animal to glide through narrow 

 crevices, but also no doubt helps it to escape from its enemies. 

 The butter-fish is very eel-like in appearance, but may be readily 

 recognised by the row of dark spots, of which there are usually 

 about twelve, placed at the base of the long continuous dorsal 

 fin. The tail fin is small, as are also the paired fins, but there 

 is a long unpaired fin in the region of the anus. At low tide the 

 butter-fish is usually found beneath weed or stones, but it can 

 swim readily. The young are white, almost transparent creatures, 

 but neither they nor the adults are so easy to keep alive in cap- 

 tivity as the blenny. 



We have spoken under freshwater animals of the stickle- 

 backs. Of these the common three-spined form may sometimes 

 be found in the high rock pools, especially in the vicinity of fresh- 

 water streams. The stickleback par excellence of the shore pools 

 is, however, the fifteen-spined form, which is hardy and inter- 



