MORPHOLOGY OF BACTERIA. 77 



hanging drop of gelatin or agar, and (if necessary, 

 with the aid of warming apparatus or in a well-heated 

 room) to observe and draw definite individual cells 

 uninterruptedly. 



Motile varieties always come to a standstill (ac- 

 cording to A. Fischer) before the formation of spores, 

 but they do not cast off their flagella. Certain varie- 

 ties first grow into long filaments, which at the be- 

 ginning are unsegmented. This variety includes the 

 bacillus anthracis, whose sporulation will be selected 

 as an example (vide Plate 40, Figs. VI. and III.). 



The previously homogeneous bacteria first exhibit 

 a delicate, cloudy opacity ; then, according to Bunge, 

 the very finest granules are replaced by a smaller 

 number of somewhat coarser granules, which coalesce 

 until small, rounded spores are situated at regular 

 intervals (Plate 40, Fig. VI.), and are converted grad- 

 ually into the oval, strongly refracting, ma'ture spores 

 (Plate 40, Fig. III.). 



When sporulation is complete, we find in the bac- 

 terial filament a delicate septum between two spores 

 (Plate 40, Fig. IV.). Not all segments which have 

 begun the development of spores by the formation of 

 spherical preliminary stages mature these spores. 

 Indeed, certain varieties, as the result of various con- 

 ditions of culture, gradually suffer a permanent loss 

 of the power of producing mature spores and form 

 only preliminary stages, which are physiologically 

 valueless (Roux, K. B. Lehmann). 



According to Lud. Klein (C. B., VII., 440), spor- 

 ulation is entirely different in five usually motile, an- 

 aerobic forms of bacilli (bacillus De Baryanus, Solm- 

 sii, Peroniella, macrosporus, limosus), which were 



