228 THE INFANCY OF ANIMALS 



The adult well deserves the epithet " hideous." One can 

 almost imagine its ugliness, and its hateful mode of life, 

 to have been the infliction of some jealous and infuriated 

 sorceter ! Glance for a moment at the huge flattened 

 head and enormous mouth, and note the curious disposition 

 of the rays or supporting rods of the back fin. These 

 have now become reduced to three in number and widely 

 separated. They no longer support a fin-membrane, 

 as in the larval stage. Their function has changed, for 

 they now serve as lures, the free end of the foremost 

 supporting a little tab of skin, forming a sort of flag, 

 while small tags or flaps of skin run down along the 

 sides of the head and trunk, which by their movement 

 in the water decoy fishes on the look-out for scraps. The 

 body of this vile-looking monster being partly covered 

 in mud, the dupes approach unsuspectingly, and so soon 

 as they get near the cavernous mouth it suddenly opens, 

 and with the inrush of water they are engulfed ! 



To return for a moment to the great length of the pelvic 

 fins in the larval stages of the sword-fish and angler, be 

 it noted that a similar elongation obtains also in the case 

 of the ling, and here also, as the types just referred to, 

 in the adult stage these fins are quite short. What part 

 do they play in the young ? 



The young of the Senegal polypterus, or snake-fish, afford 

 another striking illustration of the differences between larval 

 and adult stages. As will be seen from the adjoining 

 pictures, in the young of this remarkable fish, a native of 

 the rivers of Western Africa, the back and tail fins form 

 a continuous series of bony rods, the latter of considerable 

 length. Later, it will be noticed, these closely set rods 

 open out, so to speak, each becoming widely separated 

 from its neighbour, and each bearing a thin flap of skin, 



