168 TEXT-BOOK OF BACTERIOLOGY. 



volution forms, to degenerate; it seems almost as if a continued 

 nutrition with our usual food media did not agree with this micro- 

 organism. The cells, originally so distinctly rod-shaped, swell and 

 become deformed and assume irregularly-rounded forms; the cell- 

 divisions, so clearly visible in the healthy forms, disappear, the con- 

 tents become quite turbid, and one might be tempted to suppose 

 that a new variety had arisen, were it not always easy to breed 

 normal cells again from these monstrous and crippled forms by 

 employing a more suitable culture medium. 



This micro-organism possesses a marked inclination to form 

 groups of cells; as a rule, two or more are found connected, but 

 long threads are not unusual. 



Its locomotion is not very lively; it usually moves in a peculiar 

 crawling manner, which reminds one of the amceboids. 



It often bears spores, and the alteration in the appearance of 

 the cells before mentioned, the granulated arrangement, has been 

 referred to the process of sporulation. Yet we must state that 

 Ernst's method for displaying the sporogenic granules within the 

 bodies of certain bacteria does not bear out this view. Either, 

 therefore, Ernst's method must be defective, or these appearances 

 have nothing to do with sporulation. It is certain, however, that 

 when a cell begins to sporulate, this is indicated by a special ar- 

 rangement and separation of its contents. A portion of these 

 contents contracts and becomes denser, flows to a definite spot, in- 

 creases its power of refraction, takes a definitely-circumscribed 

 shape, becomes covered with a capsule of its own, and thus becomes 

 a fully-developed spore. This spore is, in the case of Bacillus mega- 

 terium, about as long as the spore-bearing cell, but much narrower, 

 and the latter does not alter its form during the whole process. 



Later the ripe spore becomes free. When it, in turn, prepares 

 for germination, the spore-membrane breaks at the middle, and the 

 young bacillus at first drags about with it the remains of the rup- 

 tured membrane, in the form of a cap at either end. 



Bacillus megaterium thrives best at a temperature of about 20° 

 C, but it can also support the temperature of the incubator. It is 

 strictly aerobic, and is quite dependent on oxygen for its existence. 

 It takes the ordinary anilin stains well, yet the granulation of its 

 cells often remains visible in the stained preparation, the separate 

 granules appearing now darker, now lighter, than the rest of the 

 cell-contents. The fully-formed spores are easily made conspicuous 

 by the ordinarj' process of spore-staining. 



On the gelatin plate Bacillus megaterium grows -with moderate 

 rapidity and requires a certain time for its full development. 



