THE MYXINOIDS 



579 



Besides Myxine glutinosa, two 

 other species are known — one from 

 Japan, another from the Magellan 

 Straits. The southern M. australis 

 Uves in shallow water close by the 

 shore, but the others live in deep 

 water. The genus Bdellostoma, 

 from the Pacific coasts of America, 

 off the Cape of Good Hope, etc., is 

 nearh'^ alhed. 



The best -known species, Bdello- 

 stoma dombeyi, resembles the hag 

 in many ways. It lives at the 

 bottom of the sea, at depths of a 

 hundred fathoms or more, and is 

 often found inside caught halibut, 

 etc. The gill-pouches have sepa- 

 rate openings, and are extraordin- 

 arily variable in number, from six 

 to foiurteen on either side — a vari- 

 ability perhaps pointing to ances- 

 tral reduction from a larger number 

 (cf. Amphioxus). Large eggs are 

 laid on a shelly or rocky bottom, 

 become connected by polar hooks 

 in chains or clusters, are fertilised 

 after deposition, and exhibit mero- 

 blastic discoidal segmentation and 

 direct development. Ayers' ex- 

 periments show that the removal 

 of one or both ears in this form 

 does not materially affect equili- 

 bration. 



Second Type. Petromyzon — 

 The Lamprey 



There are three British 

 species — the sea lamprey 

 [Petromyzon marinus), over 

 3 ft. in length ; the river 

 lampern {P.fliwiatilis), nearly 

 2 ft. long ; and the small 

 lampern or " stone-grig " (P. 

 planer i). They eat worms, 

 small crustaceans, insect 

 larvae, dead animals, etc. ; 

 but they also attach them- 





Vf'3 



Fig. 326. — Bdellostoma stouti (Cali- 

 fornian hag), enveloped in sheath 

 of mucus. — After Bashford Dean. 



b., Barbules ; e., eyes ; in., mucus ; eg., eggs. 



