212 THE ROUND-MOUTHED FISHES 



are especially harmful to the cod-fisheries. Swarms of Hags will 

 attack the fishes caught on the hooks of the long lines, boring 

 their way into their bodies and devouring almost all the flesh 

 with the aid of their powerful rasping tongues. In this way the 

 Hags are said sometimes to destroy whole " catches " of cod, 

 ling, and haddock, nothing remaining of the fishes when the lines 

 are drawn in but mere shells of skin and bones. It is not known 

 whether the Hags attack free-swimming fishes, or confine them- 

 selves to attacking those which are hooked or netted, injured or 

 dead; but captured or maimed fishes appear to be their natural 

 prey. The Common Hag-fish (Myxine glutinosa) of the North 

 Atlantic is responsible for most of the mischief done to the British 

 cod-fisheries ; its depredations are sometimes so extensive that 

 the North Sea fishermen are forced to change their fishing-ground. 



The Pacific Hag, common on the seaboard of North America, 

 does just as much damage, and an interesting account of its ways 

 has been given by Miss Julia Worthington in the American Naturalist. 

 She writes : " When the night lines are examined, one-third or 

 more of the hooks hold Hag-fish, and the fish on many of the others 

 have been entirely eaten away, nothing but the skin and bones 

 being left. The Hag-fish has bored inside the skin and eaten all 

 the soft parts, and is sometimes caught in the very act of wriggling 

 away at the close of its meal when the fish is taken from the water. 



" The Hag does not really suck the captured fishes, but it 

 presses against them and rasps off pieces of skin and muscle. If 

 the fish is a large one, the Hag makes a hole through the body- 

 wall and goes inside. Several often work together, and I have 

 seen three or four inside one fish. In captivity they eat at long 

 intervals and seem able to remain vigorous on a minimum of 

 food. From the nature of their diet it seems likely that oppor- 

 tunities for meals are not frequent in natural conditions, and 

 it is probable that Hags have become constitutionally adapted 

 to do with little food. 



"On the ventral wall of the pharynx there is a paired tooth- 

 plate, which some regard as representing the lower j aw. Each half of 

 this plate bears two rows of horny teeth, pointing backwards. When 

 the Hag feeds, the tooth-plate is thrust out of the mouth, and its 

 fore end is drawn down so that it takes a position almost per- 

 pendicular to the long axis of the body. The two halves are at the 



