Fishes Photoblepharon and Anomalops. 55 



TEMPERATURE. 



The temperature of the water in which these fish normally live 

 varies but Httle from 27° C. the year around. If a sea-water extract 

 of the luminous organ of Anomalops is made and gradually heated in 

 a test-tube, the light dims at 38° and disappears at 41° to 42°. If 

 cooled quickly, the light returns and the heating and cooling can 

 be repeated several times with alternate disappearance and reap- 

 pearance of luminescence. If heated to about 50° and cooled quickly, 

 there is no return of the light, but there is some recovery on heating 

 to 48° and cooling quickly. 



An extract of Photoblepharon behaves in just the same way as 

 Anomalops on heating under similar conditions, except that the light 

 dims at 40° and disappears at 43° to 44°. Heating to the neighbor- 

 hood of 51° likewise extinguishes the light permanently. 



It should be noted that there is no marked increase in brightness 

 on slight heating, so characteristic of extracts of pennatulids and jelly- 

 fish. The sudden brightness in these forms I would interpret to be 

 a heat cytolysis of cells containing luminous material or perhaps 

 a granulolysis of hght-producing granules. In the absence of this 

 heat-effect these fish again resemble luminous bacteria. The temper- 

 ature of extinction is significant, lying as it does in the neighborhood 

 of 40°. This is the general region for extinction of the hght of lumi- 

 nous bacteria, whereas Cypridina, Cavermdaria, and several other 

 luminous forms which produce light are affected only by much higher 

 temperatures. 



SPECTRUM AND INTENSITY. 



Steche reported the intensity of the light of Photoblepharon to be 

 0.0024 meterkertze. This value was arrived at by determining in 

 Banda that he could just read his watch easily by the luminescence 

 of the fish at a distance of 2 meters, after a 5-minute dark adaptation 

 of his eyes. On arrival home, Steche prepared an illuminated slit 

 giving about the same intensity and color as the light of Photo- 

 blepharon, and found he could read his watch at a distance of 1.75 

 meters after a 5-minute dark adaptation. The intensity of the slit 

 was therefore 0.75 of that of the luminous organ, and in comparison 

 with a candle the slit was found to be 0.0018 meterkertze. Hence 

 the intensity of one light-organ of a fish was four- thirds of 0.0018 

 meterkertze or 0.0024 meterkertze. I have made no measurement 

 of the intensity of the light of these fishes, but may remark in passing 

 that it is extraordinarily bright and the living fishes present a remark- 

 able sight as they swim through the water flashing their lanterns — 

 so large in proportion to the body — like great electric torches. 



To my eyes the color of the light of both Anomalops and Photo- 

 blepharon is greenish blue. In lamplight it looks green, as does an 



