422 



FISHES 



supplying them have atrophied. The embryonic pronephros is 

 retained in the adult. The eggs are large ; segmentation is 

 meroblastic ; and development is direct, without a larval meta- 

 morphosis. Two families can be distinguished. 



Fam. 1. Myxinidae. — Gill-sacs not exceeding six pairs, with 

 a common external aperture on each side of the body. 



The family includes a single genus, Myxine, of which the 

 common Hag {M. glufinosa) from the North Atlantic is the best 

 known species (Figs. 92, A, and 240). This Hag-Fish occurs 

 off the coasts of Northern Europe, including the British Isles, as 

 well as on the Atlantic sea-board of North America,^ southwards 

 to Cape Cod. Other species are found off the coasts of Chili 



Fig. 240. — Myxine glutinosa. A, lateral view; B, view of the ventral surface of the 

 head, showing the month and tentacles, l.l.p. Lateral pore-like apertures of the 

 mucus-sacs ; v, anus. 



and Japan. Myxine is quasi-parasitic in its habits, boring its 

 way into the bodies of large Fishes. By means of its rasping 

 " tongue " it devours all the soft parts of its prey, leaving little 

 more than a mere shell of skin and bones. The Fishes usually 

 attacked are the Cod and other Gadoids, but the Sturgeon is not 

 immune, and the presence of a Hag in the abdominal cavity of a 

 Shark {Lavxnci cornubica) has been recorded. Myxine has the 

 reputation of being very destructive to Fishes caught on lines, 

 and it is said that whole " catches " have been destroyed by its 

 depredations, so that North Sea fishermen have been forced to 

 change their fishing-ground. To what extent the Hags attack 

 Fishes which are living and free is somewhat uncertain, but the 

 little evidence obtainable seems to point to the conclusion that, 

 as a rule, they only prey on Fishes when the latter are hooked or 

 netted, or injured or dead. When not seeking food the Hag lives 



' The American Hags probably belong to a distinct species, M. limosa Girard ; 

 Bashford Dean, Science (N.S.), xvii. 1903, p. 433. 



