One of our seven wise men once said to me, "Have you observed that in
the inorganic world things go by even numbers, and in the organic world
by odd?" I immediately went down to the edge of a bushy and swampy
meadow below our camp and brought him a four-petaled flower of galium,
and a plant-stalk with four leaves in a whorl. In another locality I
might have brought him dwarf cornel, or the houstonia, or wood-sorrel,
or the evening-primrose. Yet even numbers are certainly more suggestive
of mechanics than of life, while odd numbers seem to go more with the
freedom and irregularity of growing things.
One may make pretty positive assertions about non-living things.
Crystals, so far as I know, are all even-sided, some are six and some
eight-sided; snowflakes are of an infinite variety of pattern, but the
number six rules them. In the world of living things we cannot be so
sure of ourselves. Life introduces something indeterminate and
incommensurable. It makes use of both odd and even, though undoubtedly
odd numbers generally prevail. Leaves that are in lobes usually have
three or five lobes. But the stems of the mints are four-square, and the
cells of the honey bee are six-sided. We have five fingers and five
toes, though only four limbs. Locomotion is mechanical and even numbers
serve better than odd. Hence the six-legged insects. In the inorganic
world things attain a stable equilibrium, but in the living world the
equilibrium is never stable. Things are not stereotyped, hence the
danger of dogmatizing about living things. Growing Nature will not be
driven into a corner.