As the plane touched down in Barcelona on a Saturday afternoon in September 1998, Alejandro Sánchez Alvarado was excited to see the runway pavement slick from a recent rainfall. Rain would have filled up the abandoned fountains in Parc de Montjuïc where he and Phil Newmark hoped to trap their quarry.

The two hurried in a cab to the nearest butcher for a slab of sheep’s liver, their target’s preferred dinner, and then went straight to their hotel room to fashion traps by stuffing the liver bait into empty bottles. They needed to set the traps in half a dozen of the park’s fountains before nightfall. They had only a long weekend and they were taking a big gamble that their traps would lure swarms of what they hoped would be developmental biology’s next important model organism: the planarian flatworm, Schmidtea mediterranea.

Transforming the planarian worm from a fountain-dwelling, biology classroom novelty—cut one in quarters, get four worms—to a workhorse of molecular developmental biology was an adventure both inside and outside the laboratory. The quest took Newmark and Sánchez Alvarado—and later Peter Reddien—to art stores, to amputation assembly lines, and into the genome that controls one of the most robust abilities to regrow body parts anywhere in the animal kingdom.

Illustration: Jason Holley