BARBER: HEREDITY IN CERTAIN MICRO-ORGANISMS. H 



days' beef-broth culture of the same new race. In plate II, 

 figures 1 and 2 represent respectively the parent stock and a 

 new race derived from it, both glucose agar cultures, about ten 

 days old, and grown under the same conditions. The new 

 race represented in plate II was originated about November 

 1, 1903, two years and four months before the time of photo- 

 graphing.) 



This new race has persisted three years and five months, 

 and constantly exhibits its new characteristic on a great va- 

 riety of media, and under very diverse conditions of tem- 

 perature and amount of oxygen. Some of the media tested 

 were beef-peptone broth, ordinary, and modified by the ad- 

 dition of various sugars, in amounts varying from one-half 

 to ten per cent., plain agar, and agar in combination with 

 glucose or glycerin, wort, wort gelatin, acid and alkaline, 

 glucose gelatin, Loeffler's blood serum, prune juice, and 

 Hansen's fluid medium for yeasts. Both acid and alkaline 

 liquid media were used. 



The new characteristics persisted at all temperatures em- 

 ployed, varying from low room temperature to 37i degrees 

 C, and they were found in cultures of all ages, though they 

 were less marked in cultures a few hours old. The tendency 

 to produce very elongated forms is more marked on gelatin 

 than in liquid cultures, and more pronounced in acid broth 

 than in alkaline. 



The tendency of the new race to form elongated cells is 

 well shown on gelatin or agar plate cultures, where the par- 

 ent type cultivated under these conditions shows for the 

 most part colonies with smooth outlines, while new race 

 colonies show ragged outlines, the irregularities being due to 

 outgrowing, filament-like chains of cells. (See photomicro- 

 graphs, plate IV. Figure 1, colonies of the parent type grown 

 in glucose gelatin ; figure 2, colonies of a new race of the same 

 age and grown under similar conditions.) A new race showed 

 this peculiarity over two years after its origin in as marked a 

 degree as at first. 



Colonies of both race and check were obtained in a recep- 

 tacle from which oxygen had been exhausted by the combus- 

 tion of phosphorus. These colonies were restored to air, 



