258 



LIFE, IN ITS HIGHER FORMS. 



highly instructive objects. " Examined separately," says 

 Professor Jones, " each scale is found to be partially im- 

 bedded in a minute fold of the living and vascular cutis, 

 to which its under surface is adherent. Every scale is, in 

 fact, made up of superimposed laminae of horny matter 

 secreted by the cutis, precisely in the same way as the 

 shelly covering of a mollusc; and by maceration the dif- 

 ferent layers may readily be separated, the smallest and 

 most superficial being, of course, the first formed, while the 

 largest and most recent are those nearest to the surface 

 of the living skin : as far as relates to the mode of growth, 

 therefore, there is the strictest analogy between the scale 

 of a fish and a shell. Various are the forms under which 

 these scales present themselves to the ichthyologist ; 

 sometimes, as in the Eel, they are thinly scattered over 

 the surface of a thick and slimy cutis;* more generally 

 they form a close and compact imbricated mail ; in the 

 Pipe fishes (Syngnathidce) the whole body is covered with 

 a strong armour composed of broad and thick calcareous 

 plates; and in the Coffin-fishes (Osfracioniclce) the integu- 

 ment is converted into a strong box made up of polygonal 

 pieces anchylosed together, so that the tail and the fins 

 alone remain moveable." t 



The bones which compose the proper skeleton have little 

 density or hardness in any fishes ; and in one large sub- 

 division — that containing the Sturgeons, Sharks, and 

 Skates — they are wholly composed of cartilage. In the 

 latter, which, in this as well as some other respects, are 

 the lowest forms in the Class, we find, however, analogies 

 and peculiarities which raise them above the highest. 



* Or, rather, imbedded in its substance. f "Gen. Outline," p. 506. 



