The skin is in some fishes covered with scales (the scale of a
fish is a thin and shiny film, and therefore easily becomes detached
from the surface of the body). In others it is rough, as for
instance in the Rhine, the Batos, and the like. Fewest of all are
those whose skin is smooth. The Selachia have no scales, but a rough
skin. This is explained by their cartilaginous skeleton. For the
earthy material which has been thence diverted is expended by nature
upon the skin.
No fish has testicles either externally or internally; as indeed
have no apodous animals, among which of course are included the
serpents. One and the same orifice serves both for the excrement and
for the generative secretions, as is the case also in all other
oviparous animals, whether two-footed or four-footed, inasmuch as they
have no urinary bladder and form no fluid excretion.
Such then are the characters which distinguish fishes from all other
animals. But dolphins and whales and all such Cetacea are without
gills; and, having a lung, are provided with a blow-hole; for this
serves them to discharge the sea-water which has been taken into the
mouth. For, feeding as they do in the water, they cannot but let
this fluid enter into their mouth, and, having let it in, they must of
necessity let it out again.
Pages:
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243