Hydra's Heads and Medusa's Blood 35
even more wondrous feats. When cut lengthwise, each half of the stalk
healed over without a scar and proceeded to regrow the missing tenta-
cles. Trembley minced some polyps into as many pieces as he could
manage, finding that a complete animal would regrow from each piece,
as long as it included a remnant of the central stalk. In one instance he
quartered one of the creatures, then cut each resulting polyp into three
or four pieces, until he had made fifty animals from one.
REGENERATION
BY A HYDRA CUT IN HALF LENGTHWISE
His most famous experiment was the one that led him to name his
polyp "hydra." He found that by splitting the head lengthwise, leaving
the stalk intact, he could produce one animal with two crowns of tenta-
cles. By continuing the process he was able to get one animal with seven
heads. When Trembley lopped them off, each one regrew, just like the
mythical beast's. But nature went legend one better: Each severed head
went on to form a complete new animal as well.
Such experiments provided our first proof that entire animals can re-
generate, and Trembley went on to observe that hydras could reproduce
by simple budding, a small animal appearing on the side of the stalk
and growing to full size. The implications of these discoveries were so
revolutionary that Trembley delayed publishing a full account of his
work until he'd been prodded by Reaumur and preceded in print by
several others. The sharp division between plant and animal suddenly
grew blurred, suggesting a common origin with some kind of evolution;
basic assumptions about life had to be rethought. As a result, Trem-
bley's observations weren't enthusiastically embraced by all. They in-
flamed several old arguments and offended many of the old guard. In
this respect Trembley's mentor Reaumur was a most unusual scientist
for his time, and indeed tor all time. Despite his prominence, he was
ready to espouse radically new ideas and, most important, he didn't steal
the ideas of others, an all too common failing among scientists.
A furious debarte was raging at the time of Trembley's announcement.
It concerned the origin of the individual - how the chicken came from