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Temperature

heated, light and cypridina

TEMPERATURE.

Lund (s) finds that in

Cypridina squamosa (?) and Cyclopina gracilis the light from the luminous secretion disappears at 50° and if heated above 50° (as high as 70° but not above) it will again reappear at 50°. The time factor is always involved in determining the critical points in the effects of temperature, and I find that the concentration of the light-producing substances is also involved. Therefore the exact tem perature of destruction of photephelein and photogenin depends upon their concentration and the time of heating. I find that cypridinas dried over ground, and the powder suspended in sea-water give a beautiful light which disappears when heated to 56°, but returns on cooling. If heated to 65° and cooled, the light also returns, but does not return if heated to 70° and then cooled. A very concentrated mixture of photogenin and photophelein may be heated above 70° and whole cypridinas heated to boiling will occasionally give a faint light when cooled. The light from the normal secretion of Cypridina dis

appears at 52° to 54°, and returns on cooling, so that we may regard this as the inhibition temperature and something above 70°, depending on the concentration, as the destruction temperature. These results are in good agreement with those of Lund.

The time necessary to destroy photophelein at 100° depends also upon its concentration. In dilute solution (1 Cypridina to 25 or 50 c.c. water) boiling for 1 minute is sufficient, but in concentrated solution (1 Cypridina to 1 c.c. water) 5 minutes' boiling is necessary.

In Pholas dadylus (a) photophelein (luciferin) is destroyed above 70°, whereas in the firefly (both Photuris and Luciola) it may be boiled for 10 minutes without destruction.

The luminous material of Cypridina, like that of most luminous organisms, is unaffected by cold and will glow brilliantly at 0° C.