FISHES 185 



higher vertebrates, regenerate; that is, they very 

 conveniently grow back when broken or bitten off. 

 The regenerated parts, however, are often more or 

 less twisted and do not always look quite like nor- 

 mal fins. 



Fish usually are so intent on finding something 

 to eat and so persistent in their search for food that 

 one is led to believe that they live only to eat. If 

 that is the main purpose of their lives, then it fol- 

 lows that the mouth is the most important part of 

 their anatomy, for the food of fish is not won by the 

 toil of the hand, as in man, but is captured as well 

 as eaten by the mouth. Some fish feed on very small 

 animal and plant life, and others feed on large or- 

 ganisms. Fish having small mouths generally feed on 

 small animals and plants. Since fish usually gulp 

 their food, instead of taking it a bite at a time, their 

 mouths must be large enough to receive whole what- 

 ever is eaten. It does not follow, however, that all 

 fish with large mouths feed on large organisms, for 

 some fish with big mouths merely take great mouth- 

 fuls of water and pass it over their gills, which are 

 provided with a special screening apparatus whereby 

 minute organisms are removed from the water, and 

 then, instead of swallowing the water, they let it 

 pass out at the gill openings. The pipe-fish and the 

 goose-fish offer two extremes in size of mouth. The 

 pipe-fish has only a very small opening for a mouth 

 at the end of a long tube-like snout, whereas the 

 goose-fish has such a large mouth that in some 

 regions it is known as "allmouth." Mouths of many 

 intermediate sizes and shapes are numerous. Some 



