53
See also: Robert Hooke 54 ■ Antonie van Leeuwenhoek 56–57 ■
John Ray 60–61 ■ Carl Linnaeus 74–75 ■ Louis Pasteur 156–59T
he metamorphosis of
a butterfly from egg to
caterpillar to chrysalis to
adult is a familiar process to us
today, but in the 17th century,
reproduction was viewed very
differently. Following the Greek
philosopher Aristotle, most people
believed that life—especially
“lower” creatures such as insects—
arose by spontaneous generation
from nonliving matter. The theory
of “preformism” held that a “higher”organism took its fully mature form
in its miniscule beginning, but that
“lower” animals were too simple to
have complex innards. In 1669,
pioneering Dutch microscopist Jan
Swammerdam disproved Aristotle
by dissecting insects under the
microscope, including butterflies,
dragonflies, bees, wasps, and ants.A new metamorphosis
The term “metamorphosis” had
once meant the death of one
individual followed by another’s
appearance from its remains.
Swammerdam showed that the
stages in an insect’s life cycle—
adult female, egg, larva and pupa
(or nymph), adult—are different
forms of the same creature. Each
life stage has its own fully formed
internal organs, as well as early
versions of the organs for later
stages. Seen in this new light,
insects clearly warranted further
scientific study. Swammerdam
went on to pioneer the classification
of insects based on their
reproduction and development,
before dying of malaria at 43. ■SCIENTIFIC REVOLUTION
ORGANISMS
DEVELOP IN A
SERIES OF STEPS
JAN SWAMMERDAM (1637–1680)
IN CONTEXT
BRANCH
Biology
BEFORE
c.320 BCE Aristotle declares
that worms and insects arise
by spontaneous generation.
1651 English physician William
Harvey considers the insect
larva a “crawling egg” and the
pupa a “second egg” with little
internal development.
1668 Italian Francesco Redi
provides early evidence to
refute spontaneous generation.
AFTER
1859 Charles Darwin explains
how each stage of an insect’s
life is adapted to its activity
and environment at that stage.
1913 Italian zoologist Antonio
Berlese proposes that an insect
larva hatches at a premature
stage of embryo development.
1930s British entomologist
Vincent Wigglesworth finds
hormones control life cycles.
In the anatomy of a louse, you
will find miracles heaped on
miracles and will see the
wisdom of God clearly
manifested in a minute point.
Jan Swammerdam