es and
toothed whales. It is quite possible that the open sea was the original
cradle of life and perhaps Professor Church is right in picturing a long
period of pelagic life before there was any sufficiently shallow water
to allow the floating plants to anchor. It is rather in favour of this
view that many shore animals such as crabs and starfishes, spend their
youthful stages in the relatively safe cradle of the open sea, and only
return to the more strenuous conditions of their birthplace after they
have gained considerable strength of body. It is probably safe to say
that the honour of being the original cradle of life lies between the
shore of the sea and the open sea.

The Great Deeps

3. A third haunt of life is the floor of the Deep Sea, the abyssal area,
which occupies more than a half of the surface of the globe. It is a
region of extreme cold--an eternal winter; of utter darkness--an eternal
night--relieved only by the fitful gleams of "phosphorescent" animals;
of enormous pressure--2-1/2 tons on the square inch at a depth of 2,500
fathoms; of profound calm, unbroken silence, immense monotony. And as
there are no plants in the great abysses, the animals must live on one
another, and, in the long run, on the rain of moribund animalcules which
sink from the surface through the miles of water. It seems a very
unpromising haunt of life, but it is abundantly tenanted, and it gives
us a glimpse of the insurgent nature of the living creature that the
difficulties of the Deep Sea should have been so effectively conquered.
It is probable that the colonising of the great abysses took place in
relatively recent times, for the fauna does not include many very
antique types. It is practically certain that the colonisation was due
to littoral animals which followed the food-debris, millennium after
millennium, further and further down the long slope from the shore.

The Freshwaters

4. A fourth haunt of life is that of the freshwaters, including river
and lake, pond and pool, swamp and marsh. It may have been colonised by
gradual migration up estuaries and rivers, or by more direct passage
from the seashore into the brackish swamp. Or it may have been in some
cases that partially landlocked corners of ancient seas became gradually
turned into freshwater basins. The animal population of the freshwaters
is very representative, and is diversely adapted to meet the
characteristic contingencies--the risk of being dried