48o 



MANUAL OF ZOOLOGY. 



Both the Lampreys (fig. 260, B) and the Hag-fishes (fig. 

 260, A) are vermiform, eel-like fishes, which agree in possess- 



Fig. 260. Morphology of Marsipobranchii. A, Myxine glutinosa, showing the sucker- 

 like mouth, and the two ventral openings (K) by which the water escapes from the 

 gills. B, The River Lamprey or Lampern (Petromyzon fluiriatilis), showing the 

 seven branchial apertures on the side of the neck. C, Branchial organs of Myxine ; 

 g The gullet laid open, showing the openings (six on each side) by which the water 

 enters the branchial sacs (s) ', c Canal carrying the water away from the gills, to be 

 discharged by the two ventrally-placed branchial apertures (h, K) ; i Aperture by 

 which the water is admitted to the gullet and thence to the gills. 



ing no paired fins to represent the limbs, but in having a median 

 fin running round the hinder extremity of the body. The 

 skeleton remains throughout life in a cartilaginous condition, 

 the chorda dorsalis is persistent, and the only traces of bodies 

 of vertebrae are found in hardly perceptible rings of osseous 

 matter developed in the sheath of the notochord. The neural 

 arches of the vertebrae, enclosing the spinal cord, are only 

 represented by cartilaginous prolongations. There is a par- 

 tially cartilaginous cranium, which is not, however, movable 

 on the spinal column. The mouth in the Hag-fish (Myxine) 

 is of a very remarkable character, and enables it to lead a very 

 peculiar mode of life. It is usually found, namely, embedded 

 in the interior of some other large fish, into which it has suc- 

 ceeded in penetrating by means of its singular dental apparatus. 

 The mouth (fig. 260, A) is sucker-like, destitute of jaws, but 

 provided with tactile filaments or cirri. In the centre of the 

 palate is fixed a single, large, recurved fang, which is firmly 

 attached to the under surface of the cranium. The sides of 

 this fang are strongly serrated, and it is by means of this that 

 the Hag-fish bores its way into its victim, having previously 

 attached itself by its sucker- like mouth, assisted by the action 



