Fig. 1. Feeding in Aglantha digitale. (A) A specimen floating upside down in feeding posture, tentacles extended (photograph by Claus Nielsen). (B) Cyclical sink-fishing of Aglantha. The animal sinks passively, tentacles extended (i); at the bottom of the cycle swimming ensues (ii); the animal swims upwards with tentacles contracted (iii); then it stops swimming, turns over and starts sinking again (after Mackie, 1980).