BARBER: HEREDITY IN CERTAIN MICRO-ORGANISMS. 25 



from the beginning with characteristics differing from those 

 of the type. These variations are apparently independent of 

 the immediate conditions of cultivation. 



3. New races arising from these variations are character- 

 ized morphologically by cells abnormally elongated and tend- 

 ing to adhere in groups, and by a partial loss of the power 

 of producing spores. 



4. These morphological characteristics have persisted in 

 cultures continued through three years and five months in 

 a great variety of media, and a new race successfully com- 

 petes with the parent stock when mixed with it in cultures. 



5. Selection in the direction of further modifying the new 

 races or of bringing them back to the type have alike failed 

 to permanently alter the new characteristics. 



6. There is evidence that the new races have a greater 

 power of resisting heat and drying, a slightly greater power 

 of fermenting sugars and a somewhat less power of liquefy J 

 ing wort gelatin than the type. 



II. EXPERIMENTS ON BACTERIA. 



1. Bacillus coli communis. 



In July, 1904, experiments were begun to determine whether 

 the long filaments commonly seen in cultures of Bacillus coli com- 

 munis transmit this character to offspring. A culture kindly 

 supplied by Doctor Fernbach, of the Pasteur Institute, where 

 this part of my work was begun, furnished material for the ex- 

 periments. In order to secure absolute purity, a single 

 normal cell was isolated at the beginning and experiments 

 were conducted with the progeny of this cell. 



A number of long filaments were isolated and failed to 

 grow, but finally one was obtained which began to develop 

 soon after isolation, and gave rise to a race differing morpho- 

 logically and culturally from the type. 



This July, 1904, race will be indicated by the letter A. 

 The principal morphological characteristic of race A is its 

 tendency to form long filaments in a much larger proportion 

 than the type. (See photomicrographs, plate III. Figures 1 

 and 2 represent the parent type and the new race, re- 

 spectively, both grown in bouillon under similar condi- 

 tions.) Under some conditions the culture consists nearly 



