“How would you try to determine whether two spiderwebs had been spun by spiders belonging to the same species? Would you try to identify individual vertices which correspond exactly, thereby setting up an exact map of one web onto the other, vertex by vertex, fiber by fiber, perhaps even angle by angle? This would be a futile effort. Two webs are never exactly the same; yet there is still some sort of "style", "form" what-have-you, that infallibly brands a given species' web.”