ution, a fish
diet and residential non-migratory habit, remaining as far south the
whole year round as open water will allow; whereas the other two (the
crab-eating seal and the Adelie penguin) have in common a more pelagic
habit, a crustacean diet, and a distribution definitely migratory in the
case of the penguin, and although not so definitely migratory in the case
of the seal, yet checked from coming so far south as Weddell's seal in
winter by a strong tendency to keep in touch with pelagic ice."[63]
Wilson considers that the advantage lies in each case with the
"non-migratory and more southern species," i.e. the Weddell seal and
the Emperor penguin. I doubt whether he would confirm this now. The
Emperor penguin, weighing six stones and more, seems to me to have a very
much harder fight for life than the little Adelie.

Before the Discovery started from England in 1901 an 'Antarctic Manual'
was produced by the Royal Geographical Society, giving a summary of the
information which existed up to that date about this part of the world.
It is interesting reading, and to the Antarctic student it proves how
little was known in some branches of science at that date, and what
strides were made during the next few years. To read what was known of
the birds and beasts of the Antarctic and then to read Wilson's
Zoological Report of the Discovery Expedition is an education in what one
man can still do in an out-of-the-way part of the world to elucidate the
problems which await him.

The teeth of a crab-eating seal "are surmounted by perhaps the most
complicated arrangement of cusps found in any living mammal."[64] The
mouth is so arranged that the teeth of the upper jaw fit into those of
the lower, and "the cusps form a perfect sieve ... a hitherto
unparalleled function for the teeth of a mammal."[65] The food of this
seal consists mainly of Euphausiae, animals much like shrimps, which it
doubtless keeps in its mouth while it expels the water through its teeth,
like those whales which sift their food through their baleen plates."
This development of cusps in the teeth of the [crab-eating seal] is
probably a more perfect adaptation to this purpose than in any other
mammal, and has been produced at the cost of all usefulness in the teeth
as grinders. The grit, however, which forms a fairly constant part of the
contents of the stomach and intestines, serves, no doubt, to grind up the
shells of the crustaceans, and in this way the