The Same Halt

Film this halt twice, but do not let both takes chase the octopus. On coral rubble at night, an octopus crawls across a bottom mottled with light and dark, then slows, the tips of its arms reaching into a rock crevice. Just as locomotion shifts into halting and probing, a dark band splits from the rear end of the mantle toward both sides of the body, meets at the head, and continues toward the dorsal arm tips. It is not the whole skin darkening at once, but a motion with a leading edge and a path: beginning at the rear, taken up by the two sides of the body, arriving at the arm tips only at the end. The existing continuous footage preserves this path very clearly, but it does not describe the octopus as beginning to change color only after coming fully to rest every time. Slowing, probing the crevice, and propagation across the skin are squeezed into the same brief interval; if any one verb gets there first, it may invent causality for a function that has not yet been measured.

The first take keeps filming in a direction that might track the octopus. Take comparable halts with and without a pulse, give the footage to observers to watch frame by frame, and ask only that they mark the frame in which the octopus has already stopped. The motion-camouflage claim thereby gets a test it can fail: if the dark band is still continuing the motion of the crawl that just occurred, the two judgment times should be stably offset; if they are not offset, then even if the dark band appears at the same time as the halt, it has not produced the perceptual consequence required by that explanation. The clips used for comparison must also have similar movement profiles; if one stops abruptly and the other slows gradually, the displaced frames only show that the materials were not fair. The camera here is not responsible for proving whom the octopus deceived. It only waits for a moment the original footage never measured.

The dark band appeared thirty-three times in the original footage, but all thirty-three instances came from the same octopus, in the same recording. The number looks large enough to establish a pattern, but what has in fact been repeatedly added is still the skin trajectory from one camera position: it has not added an observer, nor has it recorded when the halt was perceived. It can pin down the association of this octopus’s actions on this night, but it cannot secure the consequence needed for a function. Rewind the film to the frame where the arm tip has just entered the crevice.

The second take no longer follows the octopus away. The camera stays on the crevice mouth the arm tip has probed, compares probing with and without a pulse, and records whether any body hidden inside begins to move before or after it. If the dark band is startling prey, the crucial action will not take place on the most conspicuous skin; the more faithfully the camera follows the octopus, the more likely it is to leave that result behind. Even if a body in the crevice really does move, it still has to be compared with footage in which there is no pulse but the same crevice-probing occurs; otherwise what startled it may simply have been the entering arm tip. Staying has its own cost: the octopus will move out of frame, there may be no prey in the crevice, and even if there is, it may not move. A shoot that has not yet been carried out cannot put flight into the scene in advance, nor can it count quiet as a negative finding.

So the second take does only this foolishly specific thing. The arm tip withdraws, the octopus moves toward the next piece of rubble, and the camera no longer corrects the composition, no longer retrieves the subject back to the center. It keeps watch on the same narrow crevice, preserving a short interval before and after the pulse. After the dark band reaches the arm tip, the camera remains on the rock crevice and keeps timing.