26 KANSAS UNIVERSITY SCIENCE BULLETIN. 



entirely of these long filaments. The tendency to elonga- 

 tion is more marked in newer cultures than in old, and 

 is at its maximum a few hours after inoculation of tubes. 

 After the culture is a day or two old, whether in hanging 

 drops or test-tubes, its difference from the type becomes less 

 marked, and is evidenced often only by the greater propor- 

 tion of long filaments, which may be relatively few as com- 

 pared with those of younger cultures, and, in some cases at 

 least, by the greater length of the shorter filaments as com- 

 pared with the normal. Young cultures of the race show 

 less motility than the type, due probably to the greater length 

 of filaments. Staining for flagella showed that the new race 

 possesses flagella much like those of the type. 



The new race is characterized by macroscopical peculiari- 

 ties also, especially in plain bouillon cultures at room tem- 

 perature. These cultures tend to become flocculent, the 

 flocculi often adhering to the sides of the tubes or settling to 

 the bottom, and leaving a comparatively clear liquid in the 

 part of the culture between the pellicle and the sediment. 

 In this respect the new race cultures present a striking con- 

 trast with the uniform cloudiness of the check tubes. Cul- 

 tures of the new race on agar or in glucose bouillon show to 

 the naked eye few or no differences from the type. 



On gelatin the characteristics of the new race are strik- 

 ingly different from those of the parent type. (See plate IV. 

 Figures 3 and 4 represent colonies of parent stock and race 

 A, respectively, grown in gelatin under similar conditions.) 

 The race colonies often show an outgrowth of long filaments, 

 New subcolonies are often formed on these outgrowing fila- 

 ments forming an irregular group of colonies connected with 

 a larger central one. 



Both old and nevv races readily form pellicles. The pelli- 

 cles are essentially alike on each, though in some cultures 

 the new race formed pellicles which seemed slightly thicker 

 than those of the type. 



The stability of race A has been determined by a long 

 series of subcultures on a great variety of media and under a 

 considerable range of temperature. The filamentous char- 

 acter is more marked in liquid than on solid media, and at 



