154 THE BOOK OF NATURE STUDY 



factory. Its popular name, the glutinous hag, refers to its 

 power of secreting from its skin-glands large quantities of thick 

 mucus. As the ancients said, the hag " could turn water into 

 glue." The mucus is probably in part protective ; it makes the 

 hag difficult to seize and is perhaps unpalatable. There are many 

 very remarkable peculiarities in the hag, e.g. that the unpaired 

 nostril opens into the back of the mouth. The development and 

 early history remain practically unknown. Two good authorities 

 (Cunningham and Nansen) have stated that hags below a certain 

 size serve as males, producing milt or spermatozoa, but that they 

 afterwards become females producing ova. 



FIG. 57. The hag Myxine glutinosa. The smooth eel-like body bears on each side 

 a row of mucus-glands (G), which secrete the characteristic glutinous slime. 

 Above the mouth opening is the unpaired nasal opening (N) which leads into a 

 canal conveying water to the back of the mouth. This is altogether unlike the 

 blind paired nostrils of fishes, and the explanation of the state of affairs is beyond 

 the scope of school work. The figure also shows the barbules (B) ; the breathing 

 apertures by which water passes out after traversing the gill-pouches, and the 

 anus (A). 



If a hag can be procured some interesting points may be 

 demonstrated, the opening of the " nostril " above the mouth ; 

 a stout bristle passed down this opening leads into the back of 

 the mouth, and the water used in breathing passes in along this 

 path ; two pairs of toothed combs on the piston-like " tongue " 

 or borer, and a single, likewise horny, tooth on the roof of the 

 mouth ; four pairs of sensitive tentacles near the mouth and 

 nostril ; the apparent absence of eyes ; two exhalant breathing 

 openings 3 inches or so behind the head ; a row of minute 

 pores at regular intervals down each side of the body the open- 

 ings of the mucus-glands, and so on. 



Summary. The round-mouths or Cyclostomes, represented 

 in Britain by lampreys and the hag, occupy a level quite dis- 

 tinctly below that of fishes. Thus they are limbless and scale- 

 less, without definitely developed jaws, and have peculiar pouch- 



