xin BACKBONED ANIMALS 271 



The lampreys (Petromyzon) live in rivers and estuaries, 

 and also in the wider sea. They are eel-like, slimy 

 animals. The skeleton is gristly ; the simple skull is 

 imperfectly roofed ; the nostril is unpaired and far baek 

 on the head ; the rounded mouth has horny teeth on the 

 lips and on the piston-like tongue ; there are seven pairs 

 of gill-pouches which open directly to the exterior and 

 internally into a tube lying beneath and communicating 

 with the adult gullet ; the young are blind and otherwise 

 different from the parents, and may remain so for two or 

 three years. 



Though lampreys cat worms and other small fry, and 

 even dead animals, they fix themselves aggressively to 

 fishes, rasping holes in the skin, and sucking the flesh 

 and juices. They also cling to stones, as the name 

 Petromyzon suggests. 



Some species drag stones into a kind of nest. They 

 spawn in spring, usually far up rivers, for at least some 

 of the marine lampreys leave the sea at the time of breed- 

 ing. The young are in many ways different from the 

 parents, and that of the small river lampern (Petromyzon 

 branchialis} used to be regarded as a distinct animal 

 Ammoccetes. The metamorphosis was discovered two 

 hundred years ago by Baldner, a Strasburg fisherman, 

 but was overlooked till the strange story w r as worked 

 out in 1856 by August Miiller. Country boys often call 

 the young lampreys " nine-eyes." and the Germans also 

 speak of Neun-augen. 



The sea lamprey (P. marinus) may measure three feet ; 

 the river lamprey (P, fluviatilis) about two feet ; the 

 small lampern or stone-grig (P. branchialis or planeri) 

 about a foot. The flesh is well known to be palatable. 



The glutinous hag (Myxine glutinosa) is an eel-like 

 animal, about a foot in length, of a livid flesh colour. 

 It is common at considerable depths (40 to 300 fathoms) 

 off the coasts of Britain and Norway, and, wiien not 

 feeding, lies buried in the mud with only its nostril 

 protruded. Like the lamprey, it has a smooth slimy 

 skin, a gristly skeleton, a round suctorial mouth with 

 teeth. The single nostril communicates with the food- 



