sense-organs comparable to the
lateral-line-system of fishes. Consequently, it would seem that when
below the surface of the water they must depend chiefly upon the sense
of hearing. Probably this sense is so highly developed as to enable the
animals, in the midst of the vibrations made by the screw-like movements
of the tail, or flukes, to distinguish the sound (or the vibrations)
made by the impact of water against rocks, even in a dead calm, and, in
the case of piscivorous species, to recognize by the pulse in the water
the presence of a shoal of fish. Failing this explanation, it is
difficult to imagine how whales can find their way about in the
semi-darkness, and avoid collisions with rocks and rock-bound coasts.

In the Christiania _Nyt Magazin for Naturvidenskaberne_, vol.
xxxviii., Dr G. Guldberg has published some observations on the
body-temperature of the Cetacea, in which he shows how extremely
imperfect is our knowledge of this subject. As he remarks, it is a
matter of extreme difficulty to obtain the temperature of living
cetaceans, although this has been taken in the case of a white-whale
and a dolphin, which some years ago were kept in confinement in a pond
in the United States. With the larger whales such a mode of procedure
is, however, obviously quite impracticable, and we have, accordingly,
to rely on _post-mortem_ observations. The layer of blubber by which
all cetaceans are protected from cold renders the _post-mortem_
refrigeration of the blood a much slower process than in most mammals,
so that such observations have a much higher value than might at first
be supposed to be the case. Indeed, the blood-temperature of a
specimen of Sibbald's rorqual three days after death still stood at 34
deg. C. The various observations that have been taken have afforded
the following results in individual cases: Sperm-whale, 40 deg. C.;
Greenland right-whale, 38.8 deg. C.; porpoise, 35.6 deg. C.; liver of
a second individual, 37.8 deg. C.; common rorqual, 35.4 deg. C.;
dolphin, 35.6 deg. C. The average blood-temperature of man is 37 deg.
C., and that of other mammals 39 deg. C.; while that of birds is 42 C.
The record of 40 deg. C. in the case of the sperm-whale seems to
indicate that at least some cetaceans have a relatively high
temperature.

With the possible exception of one West African dolphin, all the Cetacea
are predaceous, subsisting on living animal food