25 8 
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 lamina) 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 courso, 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, thero 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 aro 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 (Syngnathidai) the wholo body is covered with 
a strong armour composed of broad and thick calcareous 
plates; and in the Coffin-fishes ( Ostracionida : ) the integu- 
ment is converted into a strong box made up of polygonal 
pieces anchyloscd together, so that the tail and the fins 
alone remain moveable.” + 
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, rattier, imbedded in its substance. t “Gen. Outline," p. 506. 
