Fig. 6. Percentage of newts swimming upstream to the site of 10^–5 mol l^–1 arginine or stream water (control) release. Inert silicon gel was applied either to the forehead (control) or to the nares of newts to block the nasal cavities. Asterisk denotes a significant difference between newt responses to arginine and control (stream water) solutions, using a Fisher exact test (P<0.01).