The sun., 1903-06-14
air has been squeezed 1t was cup, wide

| air has been squeezed III was cup, "iue
| open in front.
The outer surface of this cup consisted
| of the motor cells. The inner surface con-
sisted of feeding cells, Now, when the cup
| glded forward, the food that met 1t swan
straight into the open cup. And. since
the entire inner side of that cup consisted
of feeding cells the food went directly to
the right place.
| And this adjust ment of cells brought other
advantages with it. The feeding and digest
| ing cells were protected much better now
| against enemies and accidents than they
had been when they were on the exposed
surface Of a sphere. And the connection
between them and the motor cells was
immeasurably better, Their supply OF
nourishment could be given to them
| constantly.
Now, suppose person who knows moth
| ing at all Of cells and cell communities we're
to capture such a cup-formed mass, What
sort of animal would he imagine it to be?
| II would be clear to him that he had
before him a very simply constructed
creature, which possesses only two organs
| On the outside is skin. clothed. after the
| manner Of many animals. with fine points
hairs. The animal swims in q straight
line, propelled by the himmsring impulse
| of these hairs.
! Inside the animal has stomach, with
which it eats and digests. This combina-
| ton of only two organs omach and
skin-gives the thing a primitive appear
| ance.
| One perceives that it stands low in the
scale Of animal development. But, at any
rate, it has organs-most important,
stomach. So the beholder would say:
-Yes; it is real animal
And he would be right. But we, know
ing of cell growth, have learned how the
animal became an animal. We have learned
| how it achieved stomach.
What have explained simply and with
out scientific terms is the ground principle
of the famous theory Of the gastraea.
| 1t was first formulated sharply and de-
cisively by Ernst Haeckel Springing from
the Greek word 4gaster" the stomach),
it describes that cup-shaped animal form.
whose genesis the reader has beheld. The
arch-stomach animal, we might call it in
plain English.
Haeckel furnished proof that such a
creature, with primitive division of labor,
into skin and stomach, must indeed have
| been the arch and root form OF the whole
higher animal world in the gray days Of
world evolution
The formation of primitive beings into
cell communities, cell clumps or cell
bladders, occurred repeatedly in the be-
| ginning OF life. Such cell clulnps then
developed in two wholly different directions
some in the direction of the many-celled
true plant. the others in the direction OF
the many -celled true animal
The plant shows no stomach in the sense
Of the stomach Of the animal Even though
some higher plants-the so-called insec-
tivorous plants-produce Juices like the
gastric juices and digest captured insects.
the process has nothing in common with
genuine stomach and inal formation.
| But In all animals-with the exception
Of only a very few olegenerated parasites
the stomach is the most characteristic organ
and one that is developed even where the
nervous system still is lacking.
So the beginning of the stomach. the
appearance in the world of the arch-stom-
ach animal. or gastr,a, is the great vital
moment in the life history Of the higher
animals.
III the family tree of these higher animals,
as Haeckel has worked it out, the Rastraa
forms the point Of departure for all rami-
fications. all upward development, Two
| w
ming, working out by two different methods
the mode Of life Of the cell cup.
In one branch the living cup gave up
its swimming life and fastened itself to
the ocean bottom with its lower, closed
side thus becoming the ancestor OF the
animal sponges and the polyps. In the
other branch 1t continued to swim or crawl
straight ahead and thus gradually extend
itself lateraly.
This led finally TO a symmetrical develop
ment OF both ends. An opening appeared
at the end opposite the cup or mouth.
With that opening the cup-creature
became tube. The intestine had formed.
| The creature was a worm
The worm, in turn, became the primor-
dial ancestor OF the highest animals--the
soft creatures, such as mollusks, the prickle
skins, such AZ sea stars; the articulated
animals. such as crabs spiders, insects;
and the vertebratee.
And the vertebrate. that began with
the fish. ended in the mammal with man.
The true, primitive gastrea has not