April 1, 1921] 



SCIENCE 



315 



unite to a reservoir whicli opens to tlie sea 

 water by a pore. The pores are quite regu- 

 larly arranged over the outer surface of the 

 organ from which the light emerges. 



Despite the general appearance of an organ 

 of external secretion, no luminous material 

 is excreted to the sea water by the living fish. 

 This rather unusual fact has, I believe, its 

 meaning. If the organ is tested in sea water 

 and examined under the microscope, in- 

 numerable motile rod-shaped bacteria, some- 

 times forming spirilla-like chains, can be 

 seen. Smears of the organ, which I obtained 

 in Banda, have been very kindly stained for 

 me by Professor Dahlgren, of Princeton Uni- 

 versity, and show the bacteria nicely. 



In chemical respects an emulsion of the 

 organ behaves just as an emulsion of luminous 

 bacteria and differs in one or another way 

 from extracts of other luminous animals. 

 These various characteristics may be summar- 

 ized as follows: 



1. The light organ is extraordinarily well 

 supplied with blood vessels and the emulsion 

 fully as sensitive to lack of oxygen as are 

 luminous bacteria. Light ceases very quickly 

 in absence of oxygen. 



2. If dried, the'organ will give only a faint 

 light when again moistened with water. This 

 is characteristic of luminous bacteria. The 

 luminous organs of most other forms can be 

 dried without much loss of photogenic power. 



3. Luciferin and luciferase can not be 

 demonstrated. 



4. The light is extinguished without a pre- 

 liminary flash by fresh water and other cyto- 

 lytic (bacteriolytic) agents. 



5. Sodium fluoride of 1 to 0.5 per cent, 

 concentration extinguishes readily the light 

 of an emulsion of the gland. 



6. Potassium cyanide has an inhibitive effect 

 on light production in about the same con- 

 centration as with luminous bacteria. 



To these observations must be added the 

 very suggestive fact that the light of Phoio- 

 plepharon and Anomalops continues night and 

 day without ceasing and quite independently 

 of stimulation. This is a characteristic of 

 luminous bacteria and fungi alone among 



organisms, and very strongly suggests that 

 the light is actually due to symbiotic lumi- 

 nous bacteria. The organ becomes, then, an 

 incubator for the growth and nourishment of 

 these forms and we may perhaps look upon 

 the pores mentioned above as a means of 

 exit for dead bacteria. Otherwise their exist- 

 ance would be inexplicable in an organ which 

 certainly does not produce an external 

 secretion. 



Actual proof that the bacteria found in the 

 organ are luminous can only come when these 

 are grown artificially. My attempts in this 

 direction have failed. Good growths of bac- 

 teria were obtained on pepton-agar but they 

 produced no light. One might expect that a 

 symbiotic form would require rather definite 

 food materials to produce light and it is, 

 perhaps, not surprising that culture experi- 

 ments have failed. We have Giard and Billet's 

 experience with the form infecting sand fleas. 

 This could be grown artificially but only pro- 

 duced light when infecting the sand fleas 

 themselves. Certainly, the ocular and chem- 

 ical evidence, if not the cultural evidence, 

 supports the view that the light of these living 

 fish is bacterial in origin. A complete ac- 

 count of the fish will appear shortly in the 

 Carnegie Institution Publications. 



E. Newton Harvey 

 Princeton University, 

 March 1, 1921 



THE AMERICAN ASSOCIATION FOR 



THE ADVANCEMENT OF SCIENCE 

 SECTION L— HISTORY OF SCIENCE SESSIONS 



The growing aad widespread interest in the his- 

 tory of science, in this country, was very evident 

 during the Convocation Week (December 27- Jan- 

 uary 1), when two learned national organizations 

 held meetings in Washington, D. C, and Chicago. 

 Each of these organizations held sessions upon the 

 history of science. 



During the same week in 1919, The American 

 Historical Association inaugurated the movement 

 by holding at its Cleveland meeting, a most inter- 

 esting and successful conference.i This same asso- 



1 Science, N. S., Vol. LI., pp. 193-194, February 

 20, 1920. 



