LIGHT BY LIVING ORGANISMS McDEEMOTT. 361 



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 ( 53a ) 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 -^V (Coblentz, 5a ) to T¥ V^ (Langley and Very, 39 ) of a candle power, 

 so we would need quite a higli "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. 



i Alcock, A., "A Naturalist in Indian Seas," Lond., 1902. 



2 Barber, H. S., Free. Ent. Soc. Wash., 1908, vol. 9, pp. 41-43. 

 2a Barnard, J. E., Knowledge, 1911, vol. 34, pp. 190-192. 



a Bongardt, J., Zeitschr. wissensch. Zool., 1903, vol. 75, pp. 1-45. 



* Coblentz, W. W., Physikal. Zeitschr., 1909, vol. 10, pp. 955-956. 



5 Coblentz, W. W., Electr. World, 1910, vol. 56, pp. 1012-1013. 

 &» Coblentz, W. W., "A Physical Study of the Firefly." Publication No. 164, Carnegie Inst., Wash., 

 D. C, 1912. 



e Coblentz, W. W., Canad. Entomol., 1911, vol. 43, pp. 355-360; Physikal. Zeitschrift, 1911, vol.12, pp. 

 917-920. 



feConroy, Nature, London, 1882, vol. 26, p. 319. 



i 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. 



3 Delepine, M., Compt. Rend. Acad. Sci., Paris, 1910, vol. 150, pp. 870-878; ibid., 1911, vol. 153, pp. 279-282. 

 "> Distant, W. L., Trans. Ent. Soc. Lond., 1895, p. 429. 



ii Dobbs and Moffatt, Irish Nat., 1911, vol. 20, pp. 124-131. 



w Dubois, R., Bull. Soc. Zool. France, 1886, vol. 11, pp. 1-275. 



13 Dubois, R., "Lecons de la Physiologie generale et compares," Paris, 1892. 



i< Dubois, R., Ann. Rept., Smithsonian Inst., 1895, pp. 413-431. 



18 Dubois, R., Compt. Rend. Soc. Biol., 1886, vol. 3, ser. 8, pp. 518-522. 



is Dubois, R., Compt. Rend. Acad. Sci., Paris, 1893, vol. 117, pp. 184-186. 



i? Dubois, R., Compt. Rend. Soc. Biol., 1900, vol. 52, pp. 569-570. 



18 Dubois, R., Compt. Rend. Assn. Franc. Av. Sci., Toulouse, 1910. 



