444 CYCLOSTOMATA 



Regarding the Pacific hag, Miss Worthington 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 

 opportunities for meals are not frequent in natural conditions, 

 and it is probable that the hags have become constitutionally 

 adapted to do with little food. The males of the Californian 

 hag are known to be fond of the eggs, which they swallow whole. 



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

 plate — which some regard as representing the lower jaw. Each 

 half of this plate bears two rows of horny teeth pointing back- 

 wards. 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 perpendicular to the long axis of the body. 

 The two halves are at the same time drawn apart, so as to 

 present an almost flat surface. Placing this flat surface 

 against the fish to be eaten, the hag draws the halves of 

 the tooth-plate together, thus tearing off a portion of the 

 food, and then withdraws it into its mouth. It swallows the 

 food very rapidly, and immediately sticks out the tooth-plate 

 for more." * The tooth-plate is worked by five muscles, three of 

 which form a long substantial " club," which may be readily felt on 

 a spirit specimen of a hag stretching back for a couple of inches 

 behind the mouth. Myxine treats the long lines of the haddock 

 fishermen off the mouth of the Firth of Forth in the same way, 

 many taking the baited hooks into their stomachs, others 

 attacking the hooked fish. 



There is no doubt that hag are found inside fishes, but 



1 Julia Worthington, 1905. 



