Today, a biologist won't be tricked by mother
nature. The University of Houston's College of
Engineering presents this series about the machines
that make our civilization run, and the people
whose ingenuity created them.
We knew how to tell plants
from animals in 1740. Animals reproduced sexually.
Plants stayed in one place. Animals hunted. Plants
took nutrients from water and soil. The lines were
clear enough. Then a young Swiss tutor named
Abraham Trembley went to work for a wealthy patron
in Holland. Trembley spent all his free time
studying the plant and animal life on the estate.
He soon ran across a half-inch
aquatic life-form. It had a slender torso with a
mouth on top and tentacles reaching out from the
mouth. He called it a polyp. Today we call
it a hydra. It's kin to jellyfish and
corals. At first the hydra seemed to be immobile,
and Trembley took it to be a plant. Then it
surprised him. He saw it stretch out, put its mouth
to the ground, lift its base overhead, and bring it
down on the other side. It traveled by
somersaulting. Animals do things like that, but not
The hydra also sought light the way plants do.
Trembley kept up pursuit. He cut one in two to see
if a shoot would live. It did. Maybe it was a
plant, but one that could walk. So he kept watch.
Then one of these plants seized and ate prey like
an animal. But if it was an animal, it reproduced
asexually -- by budding. Some plants did that, but
no known animals.
The importance of this plant/animal link was
enormous. It took great tenacity for Trembley to
see what was there, instead of what he expected to
see. In the end, his sure observations opened the
door to a far more sophisticated level of thinking
in biology. As a part of this work, Trembley was
first to isolate protoplasm and to realize it was a
common building block of life.
Trembley published his findings in 1744. It was a
beautifully illustrated volume whose impact was
powerful. It's a testament to its revolutionary
character that it troubled some thinkers. He
blurred the plant/animal boundary, and he'd raised
theological questions. What, for example, happened
to an animal's soul if you could split it in two
without killing it?
Oddly enough, we've nearly forgotten Trembley
today. Two factors have consigned him to oblivion.
One is that he offered no body of theory -- only
dazzlingly clear observations. The other is that he
wrote in French. The mainstream of biological study
passed into an English-speaking world in the 19th
century. Most biologists simply stopped reading his
But Trembley had shown 18th-century biologists how
to gaze clearly at a world ready to tell us things.
He showed them how to suspend prejudice and see
what was right before their eyes.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds