tural History)_

AN INTRICATE COLONY OF OPEN-SEA ANIMALS (_Physophora Hydrostatica_)
RELATED TO THE PORTUGUESE MAN-OF-WAR

There is great division of labor in the colony. At the top are floating
and swimming "persons"; the long ones below are offensive "persons"
bearing batteries of stinging cells; in the middle zone there are
nutritive, reproductive, and other "persons." The color of the colony is
a fine translucent blue. Swimmers and bathers are often badly stung by
this strange animal and its relatives.]

[Illustration: A SCENE IN THE GREAT DEPTHS

Showing a deep-sea fish of large gape, two feather-stars on the end of
long stalks, a "sea-spider" (or Pycnogon) walking on lanky legs on the
treacherous ooze, likewise a brittle-star, and some deep-sea corals.]

The fauna of the shore is remarkably _representative_--from unicellular
Protozoa to birds like the oyster-catcher and mammals like the seals.
Almost all the great groups of animals have apparently served an
apprenticeship in the shore-haunt, and since lessons learned for
millions of years sink in and become organically enregistered, it is
justifiable to look to the shore as a great school in which were gained
racial qualities of endurance, patience, and alertness.

II. THE OPEN SEA

In great contrast to the narrow, crowded, difficult conditions of the
shore-haunt (littoral area) are the spacious, bountiful, and relatively
easygoing conditions of the open sea (pelagic area), which means the
well-lighted surface waters quite away from land. Many small organisms
have their maximum abundance at about fifty fathoms, so that the word
"surface" is to be taken generously. The light becomes very dim at 250
fathoms, and the open sea, as a zoological haunt, stops with the light.
It is hardly necessary to say that the pelagic plants are more abundant
near the surface, and that below a certain depth the population consists
almost exclusively of animals. Not a few of the animals sink and rise in
the water periodically; there are some that come near the surface by
day, and others that come near the surface by night. Of great interest
is the habit of the extremely delicate Ctenophores or
"sea-gooseberries," which the splash of a wave would tear into shreds.
Whenever there is any hint of a storm they sink beyond its reach, and
the ocean's surface must have remained flat as a mirror for many hours
before they can be lured upwards from the calm of their deep retreat.

T