foetal condition), and the palate is provided with numerous
transversely placed horny plates, forming the "whalebone." Salivary
glands are rudimentary or absent. The stomach is complex, and the
intestine simple, and only in some species provided with a small
caecum. The liver is little fissured, and there is no gall-bladder.
The blood-vascular system is complicated by net-like expansions of
both arteries and veins, or _retia mirabilia_, The larynx is of
peculiar shape, the arytenoid cartilages and the epiglottis being
elongated, and forming a tubular prolongation, which projects into the
posterior nares, and when embraced by the soft palate forms a
continuous passage between the nostrils and the trachea, or wind-pipe,
in a more perfect manner. The brain is relatively large, round in
form, with its surface divided into numerous and complex convolutions.
The kidneys are deeply lobulated; the testes are abdominal; and there
are no vesiculae seminales nor an os penis. The uterus is bicornuate;
the placenta non-deciduate and diffuse. The two teats are placed in
depressions on each side of the genital aperture. The ducts of the
milk-glands are dilated during suckling into large reservoirs, into
which the milk collects, and from which it is injected by the action
of a muscle into the mouth of the young animal, so that sucking under
water is greatly facilitated.

Whales and porpoises are found in all seas, and some dolphins and
porpoises are inhabitants of the larger rivers of South America and
Asia. Their organization necessitates their passing their life entirely
in the water, as on land they are absolutely helpless. They have,
however, to rise very frequently to the surface for the purpose of
respiration; and, in relation to the upward and downward movement in the
water thus necessitated, the principal instrument of motion, the tail,
is expanded horizontally. The position of the nostril on the highest
part of the head is important for this mode of life, as it is the only
part of the body the exposure of which above the surface is absolutely
necessary. Of numerous erroneous ideas connected with natural history,
few are so widespread as that whales spout through their blow-holes
water taken in at the mouth. But the "spouting," or "blowing," of whales
is nothing more than the ordinary act of expiration, which, taking place
at longer intervals than land-animals, is performed with a grea