Fig. 4. Heading angles (means + s.e.m.) of crayfish that did and did not follow walls for the middle and end releases along the straight wall, and the corner treatment. Crayfish that followed walls had larger heading angles and these were away from the wall (negative). Angles of zero degrees indicate heading parallel to the wall. Number of animals out of 10 that were followers is given in each bar. Asterisks indicate groups of crayfish that did not follow walls (Fisher's exact P<0.05; see text).