182 THE MICHIGAN ACADEMY OF SCIENCE. 



A thin, grayish, firmly adherent film or zooglea formed upon the surface. 

 On account of the marked adherence of the growth to th'e medium it 

 could be transferred only with diflQculty. When the gelatin was melted, 

 the growth floated as a more or less folded, tenacious film which could 

 not be broken up by shaking. 



Gelatin was not liquefied. Two per cent, glucose agar and 5 per 

 cent, glycerin agar gave but little if any growth, whereas plain agar 

 was very good. In the latter case the appearance of the growth was 

 the same as that on gelatin. 



On plain potato no growth was obtained. No better results were 

 secured when the potato in Koux tubes was moistened with alkali solu- 

 tion of different strength, with or without the addition of salt. A slight 

 growth and a faint phosphorescence were obtained upon potato which 

 had been boiled in 5 per cent, sodium chloride 'solution. 



Bouillon cultures, in twenty-four hours, showed a faint, difl'use cloudi- 

 ness with little or no tendency to form a deposit. 



The organism is aerobic. Notwithstanding numerous attempts to 

 secure an aerobic culture the result was invariably negative. More 

 over, it may be stated in this connection that the light production was 

 dependent upon the free supply of air. When a phosphorescing culture 

 was sealed, the light decreased and disappeared within forty-eight hours. 

 If the sealed tube was subsequently opened, the phosphorescence re- 

 turned even after the lapse -of a week. 



With reference to the influence of temperature it may be said that at 

 37° C. no growth could be obtained. A fairly rapid groAvth and moderate 

 light production was secured at 20° to 25° C, but the best development 

 and the maximum phosphorescence occurred between 5° and 10° C. Even 

 at 0° C. the organism grew slowly and produced some light. 



The composition of the medium, and more especially its reaction, was 

 found to exert a marked influence upon light production. The fish ex- 

 tract gelatin, containing asparagiu, which is very serviceable for the 

 phosphorescing bacteria obtained from sea water, did not give as good 

 results as those given by the ordinary nutrient gelatin or agar. The 

 latter was found to be preferable for producing phosphorescence. 



The organism would not grow upon acid or extremely alkaline media. 

 The optimum reaction for the production of light was obtained when 

 the medium was decidedly alkaline. In the case of agar the amount of 

 alkali needed was relatively greater than when gelatin was used. The 

 same is true of the addition of sodium chloride, though it may be said 

 that this constituent is of secondary importance. 



Ordinary nutrient agar containing twenty-five grams of sodium chlor- 

 ide, and 2S to 35 c.c. of normal NaOH per liter, gave the best result. 

 Almost equally good results were obtained with a nutrient gelatin con- 

 taining twenty grams of salt and from 40 to 50 c.c. of normal NaOH per 

 liter. 



In the preparation of the media, it was found advantageous to add at 

 first just enough alkali to make the liquid neutral. The liquid was then 

 boiled to coagulate the albuminous constituents, after which the re- 

 mainder of the alkali was added, and upon short heating the liquid was 

 filtered and placed in tubes or flasks. In this way the desired alkalinity 

 was assured, whereas if the total amount of alkali was added in the be- 

 ginning the result was not as satisfactory, owing to the alterations 



