498 
THE OCEAN WORLD. 
find a row of teeth on the bone that forms the middle ridge of the 
palate, which is called the vornex. On each side of this is another row- 
on the palatine bones, and outside these is a third pair of rows on 
the upper jaw-bones. Some fishes have flat teeth, with a cutting edge 
in front of the jaws, like a true incisor ; others have them rounded or oval, 
adapted to bruise or crush the various substances on which they feed. 
The oesophagus connected with the mouth is short in fishes ; the 
stomach and intestines vary in form and dimensions. Digestion is very 
rapid with these beings. Most of them feed on flesh, but there are a 
few where the mouth is without teeth, which feed on vegetables. 
The growth of fishes is slow or very rapid, according to the abun- 
dance of food ; they can suffer a very long fast, but in that state they 
become diminutive in size, and finally perish of exhaustion. At certain 
seasons an irresistible impulse brings the two sexes together. Many 
species whose ordinary appearance is dull and unsightly now shine in 
the most brilliant colours. The female soon after lays her eggs, the 
number of which passes all imagination. Nature seoms to have accu- 
mulated in the body of each female myriads of eggs — a wise provision, 
which is rendered necessary by the numerous causes of destruction 
which threaten them in their native element. The eggs, abandoned 
by the females to the mercy of the waves, are fecundated after being 
deposited by the melt of the males. Such is a very brief summary of the 
organization of fishes, which have been briefly described as vertebrate, 
cold-blooded animals, breathing by means of gills ; living in water, 
moving through the water by means of their fins, and reproducing 
their kind by means of eggs, or spawn. And now a few words on 
their classification. 
Fishes naturally divide themselves into two series, according to the 
composition of their internal skeleton. This is usually osseous; never- 
theless, a whole group of them constantly retain the cartilaginous ox 
fibro-cartilaginous state. With some this frame presents even l es3 
power of resistance, and remains membranous. 
It is precisely upon this peculiarity of structure that we found the 
great division of the class of fishes into two great groups of Cartila- 
ginous and Osseous fishes, the first being again subdivided into three 
orders : namely, I. Cyclostomata. II. Selachia.. III. Sturiona. The 
second into four orders : I. Pledognathii. II. Lophobranchii • TL 
Malacopterygii. IV. Acanthoptcrygii. 
