The dolphin bears one at a time generally, but occasionally two.
The whale bears one or at the most two, generally two. The porpoise in
this respect resembles the dolphin, and, by the way, it is in form
like a little dolphin, and is found in the Euxine; it differs,
however, from the dolphin as being less in size and broader in the
back; its colour is leaden-black. Many people are of opinion that
the porpoise is a variety of the dolphin.

All creatures that have a blow-hole respire and inspire, for
they are provided with lungs. The dolphin has been seen asleep with
his nose above water, and when asleep he snores.

The dolphin and the porpoise are provided with milk, and
suckle their young. They also take their young, when small, inside
them. The young of the dolphin grow rapidly, being full grown at ten
years of age. Its period of gestation is ten months. It brings forth
its young summer, and never at any other season; (and, singularly
enough, under the Dogstar it disappears for about thirty days). Its
young accompany it for a considerable period; and, in fact, the
creature is remarkable for the strength of its parental affection.
It lives for many years; some are known to have lived for more than
twenty-five, and some for thirty years; the fact is fishermen nick
their tails sometimes and set them adrift again, and by this expedient
their ages are ascertained.

The seal is an amphibious animal: that is to say, it cannot take
in water, but breathes and sleeps and brings forth on dry land-only
close to the shore-as being an animal furnished with feet; it
spends, however, the greater part of its time in the sea and derives
its food from it, so that it must be classed in the category of marine
animals. It is viviparous by immediate conception and brings forth its
young alive, and exhibits an after-birth and all else just like a ewe.
It bears one or two at a time, and three at the most. It has two
teats, and suckles its young like a quadruped.