1. The eyes of the crab follow the movement of the sun if stationary landmarks, which would arrest the eye movement, are obscured.
2. Therefore, even if the eyes do not move when the crab is in a normal environment, the sun's movement is certainly seen by the crab.
3. The eye movements in response to tilting the whole animal only partially compensate for the body tilt. Therefore an obvious contrasting object such as the sun is not absolutely stabilized on the retina in tilting.
4. This sensory ability of the crab could form the basis of a compass response with a minimum latency of 10 sec.