Fig. 1. (A) Transverse section of the right efferent ctenidial vein of Haliotis iris filled with amaranth-stained gelatin. Haemocoelic spaces (haem.) and `lymphoid' tissue (lymph.) are marked, along with the depth (D) and width (W) dimensions. (B) Velocity flow profile with respect to probe depth range from a representative animal, showing a parabolic distribution. Points are mean flow velocities expressed as a fraction of the peak measured velocity.