Fishes Pholohlcpharon and Anomalops. 53 



ing only if dried very rapidly and if tested with water within a 

 short time after they have been desiccated. 



DILUTION. 



Despite the fact that there is so little light-material in an organ 

 of these fish which can be dried, there is an amount in the fresh 

 glands which will give a visible light when distributed through an 

 immense amount of sea-water. In one experiment with Anomalops, 

 the light-organ was carefully cut out, ground with sand in a mortar, and 

 10 c. c. sea-water added; 5 c. c. of this briUiant emulsion was then 

 diluted with equal volumes of sea-water successively until the light 

 could no longer be seen. The organ distributed in 1,280 c. c. still 

 gave a good light and in 5,120 c. c. to 10,240 c. c. the light was just 

 visible. The organ measured 12.3 by 5.7 by 1.4 mm. and the organ 

 of the opposite side weighed (fresh) about 0.08 gram. This tissue, 

 therefore, gave light visible in, let us say, about 8 liters of sea-water, 

 or 1 part in 100,000 sea-water. 



A strong emulsion of the organ is milky in appearance, due to the 

 small, suspended particles. It resembles a suspension of luminous 

 bacteria in sea-water, and like them the luminous material passes 

 ordinary filter-paper readily. As no porcelain filter was obtainable, 

 I can not say whether the particles will pass one of these or not. 



DURATION OF LUMINESCENCE. 



A concentrated sea-water extract of the luminous organ of either 

 Anomalops or Photoblepharon allowed to stand will give only a very 

 faint light after 7 hours and no light after 8j hours. More dilute 

 extracts in sea-water give light for a shorter time, as do also extracts 

 in more dilute sea-water (1 part fresh water to 2 parts sea- water and 

 1 part fresh water to 1 part sea-water). These experiments with 

 diluted sea-water were tried in the hope of getting a medium more like 

 the blood of teleosts, which usually have a salt-content considerably 

 lower than sea-water. 



If the light of these fishes is of bacterial origin, the bacteria are 

 so dependent on cultural conditions within the Uving organ that 

 they will not live for more than 7 or 8 hours when removed. The 

 organ of Anomalops or Photoblepharon kept intact in sea-water or 

 in the dead fish will also give no Hght if ground in a mortar after 

 a period of 8 hours. These experiments were performed at 29° C. 

 temperature. 



Once the light has disappeared from an extract of luminous organs 

 on standing, it can not be regenerated in any way. In this respect 

 the extract of these fish differs from those of pennatulids and jelly- 

 fish, which again give light upon addition of fresh water, and from 



