LIGHT BY LIVING ORGANISMS—McDERMOTT. 3861 
It seems to the author that the question of the relation of the 
photogenic function to the lives of the creatures possessing it has 
not had the attention it deserves. Reliable and definite observations 
are scattered, and sometimes conflicting, and there is much ground 
that has not been covered that would form an inviting field for some 
extremely interesting biologic studies. 
Moore (**) has made the interesting observation that certain 
luminous marine organisms show a diurnal periodicity of light- 
emission, even when kept in complete darkness for several days; 
this periodicity shows itself by the appearance of light at approxi- 
mately the same time in the evening and its cessation at about dawn, 
even though the creatures are kept away from light during the whole 
time of observation. 
CONCLUSION. 
We can not say now what possibilities lie before us in the discovery 
of the “‘secret of the firefly,” particularly as to the kind of ‘‘oil’’ he 
uses in his little lamp. Perhaps it will be discovered and turned to 
practical account. The emitted light of the firefly is far from being 
a good light for general illumination, in spite of its high luminous 
efficiency, on account of the very limited range of color effects pos- 
sible under it. <A single firefly has been variously estimated to give 
from #5 (Coblentz,) to 44455 (Langley and Very,**) of a candle power, 
so we would need quite a high “firefly power” to light our homes 
and streets by biophotogenic light. There are still many gaps in our 
knowledge of this interesting subject, in spite of the large amount of 
work that has already been done, but one by one we hope to close 
these up and discover the secret of the cheapest form of light. 
REFERENCES TO THE LITERATURE. 
1 Alcock, A., ‘‘A Naturalist in Indian Seas,” Lond., 1902. 
2 Barber, H. S., Proc. Ent. Soc. Wash., 1908, vol. 9, pp. 41-43. 
2a Barnard, J. E., Knowledge, 1911, vol. 34, pp. 190-192. 
3 Bongardt, J., Zeitschr. wissensch. Zool., 1903, vol. 75, pp. 1-45. 
4 Coblentz, W. W., Physikal. Zeitschr., 1909, vol. 10, pp. 955-956. 
5 Coblentz, W. W., Electr. World, 1910, vol. 56, pp. 1012-1013. 
6a Coblentz, W. W., ‘‘A Physical Study of the Firefly.’’ Publication No. 164, Carnegie Inst., Wash., 
D. C., 1912. 
6 Coblentz, W. W., Canad. Entomol., 1911, vol. 48, pp. 355-360; Physikal. Zeitschrift, 1911, vol.12, pp. 
917-920. ’ 
6a Conroy, Nature, London, 1882, vol. 26, p. 319. 
7 Dahlgren and Kepner, “Principles of Animal Histology,” chap. x, pp. 122-140,N. Y., 1908. 
8 Davy, H., Beddoes Contr. Phys. and Med. Knowledge, 1799, p. 143. 
9 Delépine, M., Compt. Rend. Acad. Sci., Paris, 1910, vol. 150, pp. 876-878; ibid., 1911, vol. 153, pp. 279-282. 
10 Distant, W. L., Trans. Ent: Soc. Lond., 1895, p. 429. 
11 Dobbs and Moffatt, Irish Nat., 1911, vol. 20, pp. 124-131. 
12 Dubois, R., Bull. Soc. Zool. France, 1886, vol. 11, pp. 1-275. 
18 Dubois, R., “‘Lecons de la Physiologie generale et comparée,” Paris, 1892. 
14 Dubois, R., Ann. Rept., Smithsonian Inst., 1895, pp. 413-431. 
16 Dubois, R., Compt. Rend. Soc. Biol., 1885, vol. 3, ser. 8, pp. 518-522. 
16 Dubois, R., Compt. Rend. Acad. Sci., Paris, 1893, vol. 117, pp. 184-186. 
17 Dubois, R., Compt. Rend. Soc. Biol., 1900, vol. 52, pp. 569-570. 
18 Dubois, R., Compt. Rend. Assn. France. Av. Sci., Toulouse, 1910. 
