546 '^h^ Philippine Journal of Science im 



pure blue, which had been carried through 11 daily transfers 

 on bouillon, gave all typical blue cultures with secondary 

 colonies. 



This experiment indicates: First, that with daily transfer in 

 broth the pure types remain pure; and, secondly, that in com- 

 petition with the blue the red tends to gain the upper hand, 

 although in 1 tube the blue predominated and in 2 tubes the red 

 and blue persisted side by side. 



After the one-day incubation, all broth tubes of this series 

 were kept at room temperature. In order to ascertain the 

 varying proportions of the red and the blue strains at different 

 stages of the experiment, samples were taken from the first, 

 fourth, and eighth transfers of A, and put into broth to get 

 actively growing cells. From these, single cells were isolated 

 and their descendants tested on maltose agar. Of 13 cells of 

 the first transfer, 7 gave blue and 6 red cultures. Of 7 cells 

 from the fourth transfer, 6 gave blue and 1 red cultures. Of 

 15 from the eighth transfer, all gave blue. 



For confirmation, a second mixed series in ordinary broth was 

 undertaken. Here 4 tubes were given equal mixture^ by the 

 method described above and 1 by simply adding a loopful of 

 each type. Two pure red and 2 pure blue cultures were added 

 to the series, and daily transfers and daily tests made as in 

 the previous experiment. The same batch of maltose agar was 

 used in all tests. On account of an enforced absence from the 

 laboratory, the experiment had to be interrupted two weeks, 

 between the first and second transfers, but all were kept in the 

 refrigerator during the interval, and in a comparative experi- 

 ment this interruption ought not to vitiate the results. 



The blue and the red controls retained their characteristics 

 after 10 transfers; and, of the mixed ones, 3 became acid at 

 the fifth; 1, the tube inoculated with the loop mixtures, at the 

 seventh; and 1, B, showed mixed red and blue at the tenth 

 transfer. Twenty-one single-cell isolations from B gave 19 blue 

 and 2 red cultures. Nineteen isolations from A, a tube which 

 had received an equal mixture of the blue and red strains and 

 had become red, gave 19 all red cultures. 



In a third mixed series, all were passed through daily 

 transfers in three kinds of broth — plain, maltose, and mannite. 

 The sugar broths were made by adding to water 1 per cent 

 peptone, 0.5 per cent salt, and 1 per cent of mannite and maltose, 

 respectively. The bacterial mixtures were made by adding to a 

 broth tube equal quantities (about 0.25 cubic centimeter) of each 



