Man In The Modern World

THE SIZE OF LIVING THINGS

in descending order, come sheep, swans, and the largest known
crustaceans.

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So much for necessary introduction; now for the facts. The
largest organisms are vegetables, the big trees of California, with a
weight of nearly a thousand tons. A number of other trees exceed the
largest animals in weight, and a still greater number in volume. The
largest animals are whales, some of which considerably exceed one
hundred tons in weight. They are not only the largest existing
animals, but by far the largest which have ever existed, for the mon-
strous reptiles of the secondary period, which are often supposed to
hold the palm for size, could none of them have exceeded about fifty
tons. Some of the lazy great basking sharks reach about the same
weight; so, since we shall never know the exact size of the dinosaurs,
the second prize must be shared between reptiles and elasmobranch fish.
The largest invertebrates are to be found among the molluscs;
some of the giant squids weigh two or three tons. The runner-up
among invertebrate groups is a dark horse; very few even among
professional zoologists would guess that it is the coelenterates. But so
it is. In the northern seas, specimens of the jellyfish Cyanea arctica
have been found with a disc over seven feet across and eighteen inches
thick, and great bulky tentacles five feet long hanging down below.
One of these cannot weigh less than half a ton, with bulk equal to that
of a good-sized horse. The clams come next, if we take their shell into
account, for Tridacna may weigh nearly as much as a man. If,
however, we go by bulk of living substance, the giant clam is beaten
by a crustacean, the giant spider crab from Japanese seas.
Then come a number of groups, all of which manage to exceed
one kilogram, but fall short of ten. There are the hydroid polyps,
with the deep-water Branchiocerianthus which, rooted in the mud,
and with gut subdivided into hundreds of tiny tubes for greater
strength, stands over a yard high and sifts the slow-passing deep-sea
currents for food with its net of tentacles, adjusted by being hung
from an obliquely-set disc. There are the largest marine snails; the
largest lamp-shells; the largest sea-urchins, starfish, sea-cucumbers,
and sea-lilies; and, rather surprisingly, the largest bristle-worms,
both marine forms and earthworms. Possibly the largest tapeworms,
such as Bothriocephalus latus, which may reach a length of over seventy
feet of coiled living ribbon in human intestines, just come into this
class, though their flatness handicaps them.
The insects and spiders come far below, the largest beetles and