Evening star., 1936-02-08

Millions Of years were required for
fishes to learn to swim"
The race first appears about $50 ,000,- =
900 years ago-in the so-called Silurian
age of the eologists-composed OF gro
tesque, clumsy armored creatures who
crawled over the cold ooZe of the sea
bottoms with very little capacity, If any,
to rise or propel themselves in the water.
The emergence from such unpro-
pitious beginnings of the swift, graceful
swimmers of today is one OF the wonder
stories of evolution.
Such are the conclusions of the noted
Norwegian paleontologist, Anatol Heintz,
in a report just issued by the Smith
Sonian Institution. based on an intensive
study of the fossil forms of fishes and
their ancestors. Many of these only
recently have come to light, mostly in
European rock formations.
Prof. Heintz brings together two fac
tors-the possible mechanical means Of
bodily propulsion in water and the actual
body builds of the earliest fishlike crea-
lures. There are, he finds, four kinds
of swimming.
The first is that of the free swimming
fishes where powerful strokes Of the tail
caused by the wavelike motion of the
whole compressed, torpedo-shaped body
drives the animal forward with great
speed, with the fms serving the purpose
of balancing and steering organs. The
second, comparable with the propulsion
of a rowboat, is seen frequently in marine
reptiles and diving birds. The limbs
serve in the capacity of oars, forcing
short, plump bodies through the water
with powerful strokes. There are no
special organs of equilibrium, or steering,
the limbs serving both purposes as well
as that Of propulsion. This is the sys-
tenn of the sea turtles and the penguins
The third, says DR.. Heintz, is the snake
like type in which the animal swimS
by means of a wavelike motion of the
entire body. AS rule median fins serve
as balancing organs. Special organs for
steering usually are absent, but the very
flexible body is able to serve this pur-
pose. The fourth type, of special i'm
portance, seems to be limited to larval
forms. 1t is unknown among fishes
reptiles, amphibians or mammals. 1t is
best exemplified by the tadpole. AS
described by DR.. Heintz:
THE large, somewhat flattened, round
ephalothorax-the head and anterior
part of the body-is without any indi-
cation of fms or other organs of equi-
librium. The tail is strongly compressed,
fairly long, with a slightly thickened
central core and wide, finlike rims above
and below. The tail of the tadpole COM
bines in itself the functions of propui-
sion, balancing and steering. The heavy
and clumsy cephalothorax participates
only quite passively In the swimming"
This last is the most inefficient of all
animal types of swimming. Tadpoles
get around clumsily in the water They
spend most of their time on the bottom.
Only when they begin to Develop limbs
do they become more active, using the
much more efficient "rowboat SYSTEM "
Few well-known fishes are built like
tadpoles. The general form is not rare,
however, among bottom dwelling forms.
Even these usually have fms to help
them steer and keep their balance on
the rare occasions when it Is necessary
for them to swim.
Now, Prof. Heintz finds, the earliest
fishes and fishlike animals were built
very much like adpoles-although they
must have been much less efficient as
swimmers because their heads and the
front parts of their bodies were covered
with protective "armor" which made it
more difficult for them to propel them
selves.
A quarter of billion years ago there
swarmed in the seas curious race of
animals knnva 10 scientists ~ 'ostra-