The Body Electric - Micro-ondes

36 The Body Electric
A HYDRA REGROWS ITS MOUTH AND TENTACLES
A PARTIALLY SPLIT HYDRA'S BODY GROWS TWO "HEADS"
the egg, for example. When scientists examined the newly laid egg,
there wasn't much there except two liquids, the white and the yolk,
neither of which had any discernible structure, let alone anything resem-
bling a chicken.
There were two opposite theories. The older one, derived from Aris-
totle, held that each animal in all its complexity developed from simple
organic matter by a process called epigenesis, akin to our modern con-
cept of cell differentiation. Unfortunately, Trembley himself was the
first person to witness cell division under the microscope, and he didn't
realize that it was the normal process by which all cells multiplied. In an
era knowing nothing of genes and so little of cells, yet beginning to
insist on logical, scientific explanations, epigenesis seemed more and
more absurd. What could possibly transform the gelatin of eggs and
sperm into a frog or a human, without invoking that tired old deus ex
machina the spirit, or inexplicable spark of life—unless the frog or per-
son already existed in miniature inside the generative slime and merely
grew in the course of development?
The litter idea, called preformation, had been ascendant for at least
fifty years. It was so widely accepted that when the early microscopists
studied drops of semen, they dutifully reported a little man, called a
homunculus, encased in the head of each sperm - a fine example of sci-