Fig. 4
From: Y-chromosomes can constrain adaptive evolution via epistatic interactions with other chromosomes
Geotaxis maze. Seven mazes were constructed in identical fashion, using 36 PVC cross junctions, 13 PVC elbow joints, 49 1 ml pipette tips embedded in hot glue, and numerous pieces of 0.5 in. diameter vinyl tubing to connect the cross junctions. Hot glue was also used to block unwanted horizontal movement (designated by diagonal lines) and pipette tips created one-way passage into an adjacent cross junction. Vials filled with food were placed at the terminal exits to attract flies. This maze provided flies with a total of 6 up or down choices