FIGURE 1. Maze-solving by Physarum polycephalum.

a, Structure of the organism before finding the shortest path. Blue lines indicate the shortest paths between two agar blocks containing nutrients: 1 (41 1 mm); 2 (33 1 mm); 1 (44 1 mm); and 2 (45 1 mm). b, Four hours after the setting of the agar blocks (AG), the dead ends of the plasmodium shrink and the pseudopodia explore all possible connections. c, Four hours later, the shortest path has been selected. Plasmodium wet weight, 90 10 mg. Yellow, plasmodium; black, 'walls' of the maze; scale bar, 1 cm. d, Path selection. Numbers indicate the frequency with which each pathway was selected. 'None', no pseudopodia (tubes) were put out. See Supplementary Information for an animated version of a–c .