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The sea snails that make them, also known as whelks, can be found in most oceans. At the peak of their reproductive cycle between October and December, female whelks release their eggs by laying them inside capsules that look like thick coins. Some whelk species string their eggs together along a common strand so that the finished product looks like a spiraling stack of poker chips. Just before the eggs are laid, a process of particular interest to Rapoport takes place within the whelks' reproductive gland, and the egg capsule transforms into an epoxy-like material.

Some whelk species anchor the encapsulated eggs to rocks or other undersea creatures, often in intertidal zones where the embryos must endure months of turbulent conditions before hatching. In that time, the capsules allow nutrients to reach the embryos from the water but keep harmful pathogens out.

Given such an environment, the capsules need a certain amount of toughness and resilience, and they also need to stretch but not retract so quickly that the recoil damages the delicate embryos. Waite, now a professor at the University of California, Santa Barbara, and his son had been fascinated to see that the capsules indeed stretched like rubber bands then returned to their original shape—very slowly.

"This is the adaptive stroke of genius that the egg capsules profit from," Waite said. "The waves are going to come in and beat the hell out of the capsule. You don't want that energy to damage the embryos, and you don't want the elastic energy to slingshot against them."