FISHES 177 



but answer to sounds in the same way as normal 

 ones. When fishes come up to be fed, it is because 

 they detect the steps of the keeper by the shaking 

 and follow them, or else they see him bringing food. 

 They have not a great cutaneous sensibility, other- 

 wise they would not bite over and over again when 

 they have been let loose by the angler.^ 



The fishes have many enemies, but the worst of 

 them all is man. It is not so much his various ways 

 of capturing fish that decimate the class as his civilisa- 

 tion that injures them as it spreads. Sometimes it is 

 factories that pour their poisonous waste into the 

 waters, and kill thousands of fishes every year. 

 Fishes are always very sensitive to bad water. The 

 tench is the only one that can thrive in water that 

 is poor in oxygen, and the mud-fish, which foretells 

 changes of weather twenty-four hours in advance by 

 its restlessness. This fish can also take air by the 

 mouth at the surface of the water. The air passes 

 into the alimentary canal, and is used up there, so 



i According to the latest works of the American expert, Parker, it 

 seems that there are fishes with a sense of hearing. In the first place, 

 he says, certain fishes of the order of the " plectognathi " (well-known 

 specimens of these are the trunk-fish and the globe-fish, the prickly, 

 swollen, globular animals that are often seen in show-cases and dealer's 

 shops), must be able to hear, because they make sounds themselves. 

 Many of them only do this in the male sex, and so the sounds may be 

 only used within their own species. These are conjectures, but Parker 

 has proved the sense of hearing with some confidence in the case of 

 one fish. This is ih.e fundulus heteroclitus, or toothed carp, an American 

 fish. The very careful experiments that Parker made with the fish 

 show that it can hear ; and the same result was obtained on making 

 an anatomical examination of its ear. It was much more like the ear 

 of the higher, hearing vertebrates in structure than the usual organ of 

 equilibrium of other fishes. 



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