In case you needed more convincing that the design of urban rail systems follows some supreme natural order comes this item in The Atlantic Cities. John Metcalfe spotlights the work of "protist-obsessed" scientist Atsushi Tero, who has led research into "the path-finding ways of Physarum polycephalum, the "many-headed slime," which survives by sending out tendrils in all directions in the quest for food."
In one stunning experiment, "researchers arranged little oat flakes on a gel in the same pattern of real cities near Tokyo in the Kanto region. Then they stimulated a slime mold to grow from the center outward, connecting with all the delicious Oatvilles in a highly precise and unappetizing game of connect-the-dots. The whole process took just over a day, and at the end there was the environs of Tokyo, outlined in ooze. (Abstract and study.)"
Researchers that have been working with slime molds believe they, "can create much more effective networks than even the most advanced technology that currently exists," and argue that, "molds will one day serve in place of human brains and computers when it comes to designing networks, whether for public transit or power lines or something else."