LIFE HISTORY OF BACILLUS ANTHRACIS. 165 



of filaments containing spores have always square or irre- 

 gular ends. When the filament remains entire, its exist- 

 ence through time can only be inferred by the spores 

 retaining exactly the same position as they occupied when 

 first formed. 



Let us now consider the changes through which the 

 spores pass in order to form rods. As a rule the spores 

 begin to escape from the filaments on the third day of 

 cultivation, and only the debris of the filaments is visible 

 on the fifth day. When they escape they are motionless, 

 bright, refractive, oval bodies, surrounded by a thin hyaline, 

 gelatinous-looking envelope, and measuring, according to 

 Cohn,^ -alwt of ^^ iiich in their long diameters (Plate XI, 

 fig. 1). 



The spores when free, according to previous observers, 

 at once grow into rods, and according to Koch at least, the 

 rod is formed out of the gelatinous-looking envelope sur- 

 rounding the spore. My observations lead me to believe 

 that the spoie does not always at once grow into a rod, but 

 that it divides into four sporules by a process of division, 

 in which the envelope, as well as the spore, takes 

 part. This division I have even seen beginning before the 

 spore escaped from the filament (PI. XI, figs. 17 and 24), and 

 that it is not a degeneration is certain, for I have watched the 

 sporules thus formed lengthen into rods. This free cell 

 formation I have had verified by many competent observers. 

 It is best seen at a temperature of 20° to 25° C, and may 

 even be seen at ordinary temperatures, and it is generally 

 found when the cultivation has been continued for seven or 

 eight days in the same drop of aqueous humour. 



This process of cell division exactly corresponds to 

 what takes place in other cells, that is, the spore elongates 

 (Plate XI, fig. 2), then becomes dumb-bell shaped, and lastly 

 divides into two round bodies, which are at first small and 

 touching each other, and enclosed by a capsule still single. 

 As they increase in size and separate from each other, the 

 capsule also becomes constricted and ultimately divides, and 

 thus we have two perfectly round, bright bodies, surrounded 

 by a thin hyaline capsule, developed from the original oval 

 spore. Each of these round bodies now undergoes the same 

 process, thus producing four sporules, all at first closely 

 adhering to each other, but soon becoming free ; and after 

 dancing about in the fluid along with others formed in a 

 similar way, settling down to form a colony (Plate XI, fig. 3), 



' ' Beitrage zur Biologic der Pflanzen,' ii, 2, 1876, p. 264. 



