AEROBIC SPORE-BEARING NON-PATHOGENIC BACTERIA 303 



the spore-bearing bacteria and has been found in dust, soil, 

 milk, water, and as a laboratory contamination. The present 

 description applies to cultures obtained from the Krai collection, 

 and from the American Museum, and to over a hundred of our 

 own isolations. 



Morphology. These are the largest of the spore-bearing 

 organisms. On plain agar in young cultures, from 8 to 24 hours 

 old, they are long and thick with homogeneous or shghtly granu- 

 lar protoplasm, measuring 0.75 to 1.25 by 3 to 9 microns. On 

 glucose agar they are even thicker measuring 1.25 to 1.5 in 

 width. On both media long forms occur but especially on glu- 

 cose agar. These may measure 30 to 45 microns in length and 

 may show homogeneous protoplasm without evident segmen- 

 tation. The protoplasm of the organism is at first homogeneous, 

 but by the end of 24 to 48 hours it is converted into a mass of 

 globular bodies resistant to the stains. These globular bodies 

 are clear, highly refractile, bulge the organism somewhat, and are 

 quite numerous six to eight appearing in each rod. They thus 

 give the organism a peculiar and characteristic appearance. 

 They show most markedly on glucose agar but are also present 

 on plain agar where they can best be demonstrated by decoloriz- 

 ing an over-stained preparation. Their nature is not clear as 

 they do not take any special bacterial stains. Shadow or 

 transparent forms appear in Bacillus megatherium early, both 

 on plain and glucose agar. These measure 1.125 to 1.5 by 4 to 

 10 microns, take the stain very faintly and show peculiar bodies 

 of agglomerated protoplasm at the sides or sometimes at the 

 ends. These transparent forms are often thicker and longer 

 and may even measure 2 by 40 to 45 microns. Occasionally 

 they are distinctly oval with rounded ends measuring about 

 1.5 by 4 microns and show a small bunch of cytoplasm at the 

 side. When these forms are in chains they are exactly like the 

 original pictures of De Bary. (Figures 31, 32, 33, 34, 35, 36, 37). 



Motility. Active progressive and rotatory motility in young 

 cultures. 



Stainifig properties. Gram-positive. 



Spore formation. Spores are formed abundantly on plain 



