ANIMAL LIFE AND THE MICROSCOPE 



are comparable to hairs and feathers. Such scales 

 are to be found in snakes and Hzards. The scales 

 of fish are of a different order but they are equally 

 or even more interesting when examined under the 

 microscope. 



If we live in a district where many and various 

 fish are caught we shall soon discover that their 

 scales differ in a remarkable degree. Some are of 

 the texture of horn, some are gristly, some bony 

 and some covered with enamel, after the manner 

 of teeth. Not only do they differ in texture but in 

 design as we shall see in a moment. 



Certain fishes, the eel is one, the mackerel another, 

 are said to be scaleless. As a fact their scales are 

 very thin and transparent and so arranged that they 

 are less evident than those of other fish. By taking 

 a little of the skin of one of these fish we can easily 

 detach a few scales for examination. Those of the 

 eel we shall find are very thin and delicate 

 and quite transparent. These and all other fish- 

 scales may be made into permanent slides by mount- 

 ing in Canada Balsam, as described in our last 

 chapter. 



The carp, whiting, salmon, sprat, herring and 

 many other fish have scales called cycloid or circular ; 

 the term is rather a misnomer because they are not 

 truly circular, but the name is used to distinguish 

 them from other scales. The structure is easily 

 made out with a moderate magnification. Many of 

 these scales, however, exhibit portions more dense 

 than the rest ; these dense spots are caused by little 



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