Observations on the Behavior of the Pteropod Creseis Acicula Rang

Descent velocities of anesthetized and non-anesthetized specimens of the pteropod Creseis acicula Rang were compared. Anesthetized specimens with wings extended descended in a vertical position at a greater velocity than non-anesthetized specimens which invariably descended in a vertical position. Anesthetized specimens in which the animal was withdrawn into the shell descended in a horizontal position at a slow velocity. Non-anesthetized animals were observed to change their rate of descent. Rate of descent is probably controlled by the angle, pitch and horizontal breadth of the wings.