barber: heredity in certain micro-organisms. 17 



room temperature and transfers were made at longer inter- 

 vals. At the end of this series, extending in all over sixty- 

 five days, cells having the character of the new race 

 reappeared in larger numbers at about the eleventh transfer 

 and continued to increase to the end. As a further test of 

 the persistence of the new race in the agar series, a transfer 

 was made from transfer No. 10 to glucose broth. The new 

 race appeared at once in a considerable proportion of cells, 

 and continued to increase proportionately to the end of a 

 broth series of six transfers. As controls, the parent type 

 and the new race, unmixed, were cultivated on agar and con- 

 tinued through seven transfers at the same intervals and 

 under the same conditions as the series just described. At 

 the end both were found to have retained their characteristics 

 unchanged. 



The original mixed broth culture was continued under the 

 same conditions as the agar series to the sixteenth subculture, 

 when the proportion of elongated cells was found to be as 

 large as in an unmixed new race culture kept as a control 

 under parallel conditions. From transfer No. 11 of this 

 mixed broth culture a transfer was made to agar and con- 

 tinued through six agar transfers under the same conditions 

 as the other agar series. The new race characteristics were 

 retained on the solid medium. 



In order to confirm the results above given, a second series 

 was begun, starting with mixed new race and parent cells, 

 each proceeding from single cells of the two types, as in the 

 first series. Cultures were continued on both glucose broth 

 and on glucose agar kept at room temperature and trans- 

 ferred six times, at intervals of about five days. In both 

 media the new race persisted as in the first series, 



• For further confirmation a third series was carried out, 

 this time not beginning with single cells but with a broth 

 culture to which five loopfuls of each type had been added. 

 Transfers were made to glucose broth, plain broth, and glu- 

 cose gelatin. These were grown at room temperature for 

 twenty-three days and transferred three times. Controls of 

 unmixed cultures of each type were carried through parallel 



2-Univ. Sci. Bull., Vol. IV, No. 1. 



