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Distribution of Photogen1n and Photophelein in the Firefly and Other Organisms

light, extract, photogenin, non-luminous and luminous

DISTRIBUTION OF PHOTOGEN1N AND PHOTOPHELEIN IN THE FIREFLY AND OTHER ORGANISMS.

While photogenin is found only in the luminous gland-cells of the firefly, photophelein is distributed throughout the body of the firefly. An extract of the non-luminous parts of the firefly will give light with photogenin, but only if tested immediately the extract is made. An extract 10 minutes old is found to contain no photophelein unless it has been previously boiled. After boiling the photophelein can be kept for many days without decomposition. There appears to be something in the extract of non-luminous parts of the firefly which causes the photophelein to disappear unless the former is destroyed by heat. That this is the case can be shown by adding unboiled extract of the non-luminous parts to photophelein, when the latter disappears from solution. Because of failure to boil the non-luminous firefly extract, I had for a long time overlooked the existence of photophelein in regions other than the luminous gland. Lack of oxygen retards but probably does not prevent the disappearance of photophelein from non-luminous parts. Note that just as photophelein disappears in contact with photogenin and oxygen with light-production, so it also disappears in contact with this substance in non-luminous parts, but without light-production. In this respect the firefly agrees perfectly with Cypridina.

Among non-luminous forms we find some whose extract will give light with photogenin, whether boiled or unboiled; others whose extract will give no light, whether boiled or unboiled. The first mentioned presumably contain photophelein not readily destroyed by standing, the second are similar to the firefly, and the third may contain no pho tophelein or some substance very quickly destructive to photophelein or an excess of acid or perhaps merely unstabile photophelein. The

exact reasons have not yet been worked out. The following extracts were tried : Note that the oxidases of blood or potato-juice will give no light with photogenin and that they also will give no light with photophelein, even if we add As we shall see later, although the oxidases can oxidize pyrogallol with light-production, they have nothing to do with light-production by animals (see p. 232).

As we have already seen (p. 182), Cypridina photophelein, if con centrated, will give a very faint light with firefly photogenin, and vice versa. Firefly photogenin and luminous bacteria prepared in the proper way (p. 214) or Watasenia seintillans photophelein (p. 223) also give a faint light, but the converse experiment fails to produce light. Cavernularia photophelein gives no light with firefly photo genin, but the converse experiment (p. 205) does. At most the light produced in any of these cross-experiments between distantly related species is very faint and again shows that photogenin and photophelein from different luminous forms possess a certain degree of specificity. As was to be expected the different combination mixtures of these substances in various genera of the Lampyridte all give light as well as the reciprocal combinations between Lampyridie and Elaterithe (Pyro phorus). Indeed, it may be found that the photogenins from different forms exhibit differences in light-giving power, depending on relation ship, similar to the differences in the hemoglobins, or similar to the specificity of the precipitin reactions of different animals.

Photophelein, on the other hand, will not give light with extracts of any non-luminous forms or with any chemical substances.