Of water animals

the genus of fishes constitutes a single group
apart from the rest, and including many diverse forms.

In the first place, the fish has a head, a back, a belly, in the
neighbourhood of which last are placed the stomach and viscera; and
behind it has a tail of continuous, undivided shape, but not, by the
way, in all cases alike. No fish has a neck, or any limb, or testicles
at all, within or without, or breasts. But, by the way this absence of
breasts may predicated of all non-viviparous animals; and in point
of fact viviparous animals are not in all cases provided with the
organ, excepting such as are directly viviparous without being first
oviparous. Thus the dolphin is directly viviparous, and accordingly we
find it furnished with two breasts, not situated high up, but in the
neighbourhood of the genitals. And this creature is not provided, like
quadrupeds, with visible teats, but has two vents, one on each
flank, from which the milk flows; and its young have to follow after
it to get suckled, and this phenomenon has been actually witnessed.