The Embryo at the Wound 49
cells, telling them what to become, which genes to activate, what pro-
teins to make, where to position themselves? It's as if a pile of bricks
were to spontaneously rearrange itself into a building, becoming not
only walls but windows, light sockets, steel beams, and furniture in the
process.
Answers were sought by transplanting the blastema to other positions
on the animal. The experiments only made matters worse. If the
blastema was moved within live to seven days after it first appeared, and
grafted near the hind leg, it grew into a second hind leg, even though it
came from an amputated foreleg. Well, that was okay. The body could
be divided
into "spheres of influence" or "organizational territories,"
each of which contained information on the local anatomy. A blastema