Body Covering 23 



aware of the theory so successfully applied in modern foot- 

 ball that a good offense is the best defense. The infant 

 swordfish starts life equipped with defensive spines and 

 rudimentary scales, and with not a sign of a sword. As it 

 grows up and produces on its face the most impressive piece 

 of offensive armament in the whole world of fishes, it com- 

 pletely abandons its defensive armor: not a scale nor a 



Figure 4. PORCUPINE-FISH 



From Jordan and Evermann, Fishes of North and Middle Americay by 

 permission of the United States National Museum. 



Spine is to be found on the body of the adult (see Figure 26). 

 And another fish, the surgeon-fish, has gone so far as to 

 change some of its defensive into offensive weapons, for it 

 has modified two of the scales at the base of its tall into 

 sharp knives, carried most of the time In sheaths in the skin, 

 but ready to swing out into action when it wishes to attack. 

 On the other hand, some fish have tended to revert to the 

 old method, and have concentrated on protection. The porcu- 

 pine-fish bristles like its namesake with spiny points, while 

 the trunk-fish's body is so stiff with horny plates that it can- 

 not bend at all, and has to depend on its tail and its fins for 

 locomotion. 



For thousands of centuries fish have had scales and men 



