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current, break and flash


When a constant current is passed through a mass of noctilucas, the animals flash brightly at the make, continue glowing during the passage of the current, and cease to glow at the break, giving no flash, but sometimes they stay glowing after the break, and in this case the stronger the current the longer the glow lasts. If stimulated mechani cally while the current is passing, they respond by a flash, just as when no current is passing.

The light comes from all parts of the noctiluca and is not restricted to anode or cathode regions. No increase in luminosity could be observed on the cathode side nor decrease on the anode side of the animal comparable with the polar effects of the current on muscle.

The tentacle movement is also influenced by the passage of a con stant current. At the make, the tentacle coils up rather tightly, like a watch-spring, and at the break it uncoils, the process being repeated for a number of makes and breaks. This tentacle response is similar to the abnormal behavior of the sartorius muscle of a frog, which some times contracts on the make, stays contracted while the current is passing, and relaxes on the break. Spaeth (1916) similarly found that

the pigment cells of fish-scales contract on the make, stay contracted during the passage, and relax on the break.

When a mass of noctilucas is subjected to the induced currents of an induction coil they respond with a flash at the break, and at the make also, if the current is strong enough.

If subjected to an interrupted induced current for 45 seconds, the animals flash on the first shock and then remain glowing, but the luminosity becomes gradually fainter. If the current is now stopped for a moment and then passed again, there is again a bright glow. The animals therefore fatigue rather readily when stimulated electri cally, as they also do with mechanical stimulation.