Imaginal Discs

How embryos “self-assemble” has fascinated thinkers for millennia. Among the ancient Greeks, Aristotle (384–322 bce) made copious observations and coined the term “morphogenesis,” which is still in use today. For the past century, the science of “developmental mechanics” has hammered at this problem relentlessly, but it is only in the last decade that the core mysteries have finally cracked. The deepest secrets have come from a fairylike fly named Drosophila melanogaster, probably the same species of “gnat” that Aristotle himself noticed hovering over vinegar slime. Unfortunately, these insights can only be fully appreciated in the arcane language of fly genetics. Hence this book full of runes and rules.

This book concerns cuticular patterns, the cellular machinery that makes them, and the genetic circuitry that runs the machinery. Although it is mainly a survey, it is also a narrative that traces the roots of our knowledge. The story that it tells – albeit in condensed form – rivals the Iliad in scope (legions of researchers devoting decades to attacking thousands of genes) and the Odyssey in wonderment (monstrous mutants posing riddles that challenge even the most clever explorer-heroes). Indeed, truth is often stranger than a fairy tale in the realm of the fly. Believe it or not, there are even remote islands where giant drosophilids with dappled wings and feathery legs have been spied dancing and fighting in the misty forests.