49 The Cyclostomes, or Lampreys 



Of Myxine, numerous species are known Myxine glutinosa, 

 in the north of Europe ; Myxine limosa, of the West Atlantic ; 

 Myxine australis, and several others about Cape Horn, and 

 Myxine garmani in Japan. All live in deep waters and none 

 have been fully studied. It has been claimed that the hagfish 

 is male when young, many individuals gradually changing to 

 female, but this conclusion lacks verification and is doubtless 

 without foundation. 



In the Eptatretidcz the gill-openings, six to fourteen in number, 

 are externally separate, each with its own branchial sac as in 

 the lampreys. 



The species of the genus Eptatretus (Bdellostoma, Heptatrema, 

 and Homea, all later names for the same group) are found only 

 in the Pacific, in California, Chile, Patagonia, South Africa, and 

 Japan. In general appearance and habits these agree with the 

 species of Myxine. The species with ten to fourteen gill-openings 

 (dombeyi : stouti) are sometimes set off as a distinct genus (Polis- 

 totrema), but in other regards the species differ little, and fre- 

 quent individual variations occur. Eptatretus burgeri is found 

 in Japan and Eptatretus forsteri in Australia. 



The Hyperoartia, or Lampreys. In the order Hyperoartia, or 

 lampreys, the single nostril is a blind sac which does not pene- 

 trate the palate. The seven gill-openings lead each to a sepa- 

 rate sac, the skin is not especially covered with mucus, the eyes 

 are well developed in the adult, and the mouth is a round disk 

 armed with rasp-like teeth, the comb-like teeth on the tongue 

 being less developed than in the hagfishes. The intestine in 

 the lampreys has a spiral valve. The eggs are small and are 

 usually laid in brooks away from the sea, and in most cases the 

 adult lamprey dies after spawning. According to Thoreau, "it 

 is thought by fishermen that they never return, but waste 

 away and die, clinging to rocks and stumps of trees for an in- 

 definite period, a tragic feature in the scenery of the river-bottoms 

 worthy to be remembered with Shakespeare's description of 

 the sea-floor." This account is not far from the truth, as re- 

 cent studies have shown. 



The lampreys of the northern regions constitute the family 

 of Petromyzonida. The larger species (Petromyzon, Entosphenus) 

 live in the sea, ascending rivers to spawn, and often becoming 



