Adaptations of Fishes 199 



they die. If lifted out of the water, the slimy hagfish at once 

 slips out and swims quickly away. In gill-nets in Monterey 

 Bay great mischief is done by hagfish (Polistotrema stouti). It 

 is a curious fact that large numbers of hagfish eggs are taken 

 from the stomachs of the male hagfish, which seems to be 



FIG. 151. Hagfish, Polistotrema stouti (Lockington). 



almost the only enemy of his own species, keeping the numbers 

 in check. 



The Swordfishes. In the swordfish and its relatives, the sail- 

 fish and the spearfish, the bones of the anterior part of the 

 head are grown together, making an efficient organ of attack. 

 The sword of the swordfish, the most powerful of these fishes, 

 has been known to pierce the long planks of boats, and it is 

 supposed that the animal sometimes attacks the whale. But 

 stories of this sort lack verification. 



The Paddle-fishes. In the paddle-fishes (Polyodon spatula and 

 Psephurus gladius] the snout is spread out forming a broad 

 paddle or spatula. This the animal uses to stir up the mud 

 on the bottoms of rivers, the small organisms contained in 

 mud constituting food. Similar paddle-like projections are 

 developed in certain deep-water Chimaeras (Harriottia, Rhino- 

 chimczra}, and in the deep-sea shark, Mitsukurina. 



The Sawfishes. A certain genus of rays (Pristis, the saw- 

 fish) and a genus of sharks (Pristiophorus, the saw-shark), pos- 

 sess a similar spatula-shaped snout. But in these fishes the 

 snout is provided on either side with enamelled teeth set in 

 sockets and standing at right angles with the snout. The 

 animal swims through schools of sardines and anchovies, strikes 



