The daily worker. [volume] (Chicago, Ill.) 1924-1958, 1926-09-02
Ernest HaeCkeh
ON last Words
on Evolution"
THE STRUGGLE OVER OUR GEN.
EALoGlcAL TREE.
Our Ape-ReIatlves and the Vertebrate
Stem.
CONTINUED from previous issue.)
CHAPTER II.


Since the great Lamarck established
the idea Of the vertebrate at the be-
ginning of the nineteenth century
(1801) and this Partisan colleague,
Cuvier, shortly afterwards recognized
the vertebrates as one of his four +
chief animal groups the natural unity
Of this advanced section of the animal
world has not been contested. In all.a
the vertebrates, from the lowest fishes
and amphibians up to the apes and
man, we have the same type of struc-
ture, the same characteristic disposi-
ton and relations of the chief organs;
and they differ materially from the
corresponding features in all other
animals. The mysterious affinities Of
the vertebrates induced Goethe, 140
years ago, long before Cuvier, to make
prolonged and laborious studies In
their comparative anatomy at Jena.
and Weimar. Just as he had, in his.
"Metamorphosis of Plants" estab-
lished the unity of organization by
means Of the leaf as the common
primitive organ, he, in the metamor-
phosis OF the vertebrates, found this
common element in the vertebral
theory of the skull. And when Cuvier
established comparative anatomy as
an independent science this branch Of
biology was developed to such an ex-
tent by the classic research of Jo-
hannes Muller, Carl Gegenbaur. Rich
ard Owen. Thos. Huxley, and many
other morphologists, that Darwinism
found its most powerful weapons in
this arsenal. The striking differences
of external form and internal structure
that we find in the fishes, anphibians.
reptiles. birds. and mammals, are due
to adaptation to the various uses OF
their organs and their environments.
On the other hand, the astonishing
agreement in their typical character.
that persists in spite of their differ
enees, is due to Inheritance from COM
mon ancestors.
The evidence thus afforded by com.
parative anatomy is so cogent that
anyone who goes impartially and at
tentively thru a collection of skele.
tons can convince himself at once Of
the morphological unity of the verte-
brate stem. The evolutionary evil
lence of comparative ontogeny, or en-
bryology, is less easy to grasp and
less accessible, but not less important.
1t came to light at much later date,
and its extreme value was only made
clear, by means of the biogenetic law.
some forty years ago. 1t shows that
every vertebrate, like every other ami.
NAL, develops from a single cell, but
that the course of its embryonic devel-
opment is peculiar, and characterized
by embryonic forms that are not found
in the invertebrates. We find in them
especially the chordula, or chorda-
larya, a very simple worm-shaped en-
bryonic form, without limbs, head, or
higher sense-organs; the body con-
sists merely of six very simple primi-
tive organs. From these are devel-
oped steadily the hundreds Of different
bones, muscles, and other organs that
we. afterwards distinguish in the ma
ture vertebrate. The remarkable and
very complex course of this embryonic
development is essentially the same in
man and the ape, and in the amphib-
ians and fishes. We see in it, in ac-
cordance with the biogenetic law, a
new and important witness to the
common descent Of all vertebrates
from single primitive form, the
chordoea.
Continued Tomorrow