22 The Life Story of the Fish 



frozen fish, and being as usual swallowed whole, was, a few 

 minutes later, coughed up alive by the startled animal, and 

 was last seen flopping back into the water through a hole in 

 the ice, having been revived by the heat of the dog's stom- 

 ach, which it probably found uncomfortably warm. 



As for aquarium fish, I have seen guppies removed from 

 the water in an experimental laboratory, and thoroughly 

 dried with blotting paper, live to tell about it to their sons 

 and grandsons, but this practice is certainly not to be recom- 

 mended. The cichlid known as the "jewel," Hemichromis 

 bimaculatus Gill, will stand a great amount of handling, as 

 was proved in this same laboratory, although with this species 

 care was taken to hold it only with wet hands or a wet cloth. 

 But it is obvious just the same that handling never does a 

 fish any good, and that, although a certain amount of it is 

 unavoidable, the less of it aquarium inhabitants get the better 

 ofl? they will be. 



SCALES 



Beneath the living skin of the fish is «dead material. For 

 the scales are as dead as our fingernails, and, like them, are 

 created by living cells which secrete or excrete the material 

 of which they are formed. In the great majority of fishes 

 there is a layer of skin over the scales. In some it is so thin 

 as to be almost invisible. In others, such as the eastern brook 

 trout, it is fairly heavy and makes the scales hard to see. In 

 still others, like the eel, it is so thick that the scales are 

 entirely hidden. 



The principal function of the scales is protection. They 

 are the remnants of the heavy armor-plate which the earliest- 

 known fossil fishes wore. As the fish became more active this 

 armor-plate had to become more flexible, and this was ac- 

 complished by breaking it up into small sections. Also, as the 

 fish acquired powerful teeth and jaws, it became less de- 

 pendent on protective armor. Mother Nature evidently was 



