168 J. COSSAR EWART. 



the spores. The spores may be found in the alimentary 

 canal of such mice, sometimes as if in process of development 

 into rods and filaments. 



Seeinoj that the rods are constantly dividing, and that the 

 spores divide into sporules, it is impossible to make any 

 definite measurement of either, and it is further scarcely 

 advisable to say that rods and spores apparently somewhat 

 smaller belong to a different species, seeing that the dif- 

 ference in size may be due to the change of habitat, the rods 

 of Bacillus anthracis b'^ing always longer, for example, in 

 Guinea pigs than they are in mice. 



The life history of Bacillus anthracis, from what has been 

 said, may be epitomised as follows : — To begin with the 

 well-known resting rod. This rod, if in living tissues, mul- 

 tiplies indefinitely by a process of transverse fission (Plate 

 XI, figs. 5 and 6j, but it never seems to lengthen ou^. into a 

 filament ; if, however, after death a sufficiently high tem- 

 perature be maintained and other conditions be favorable, it 

 may lengthen out into filaments the protoplasm of which 

 contracts into spores. 



On the other hand, if cultivated on the warm stage under 

 artificial conditions, it may become motile, though rarely ; 

 but after being alternately at rest and in motion for some hours 

 it lengthens out into an exceedingly long filament, probably 

 much longer than that found in natural conditions (Plate XI, 

 fig. 22). The protoplasm next divides into numerous segments 

 (Plate XI, fig. 9), which may again divide (Plate XI, fig. 11), 

 and then rapidly contract to form spores (Plate XI, fig. 12). 



The spores escape from the disintegrating filaments 

 (Plate XI, fig. 15), and may either at once germinate into 

 new rods or divide into four (Plate XI, fig. 2), not at all un- 

 like Protococcus. These sporules then germinate and form 

 rods similar to those with which we started (Plate XI, fig. 4). 

 Thus the cycle is completed. 



The most important morphological conclusion which 

 follows from these and other observations is that micrococcus- 

 forms, bacterium-forms, bacillus-forms, and spore-bearing 

 hyphae, are in nowise generically distinct, but that they are 

 simply phases of the same life history, a life history doubtless 

 common to all other bacteria. 



In the rarely occurring motile phase we find a condition 

 which we constantly find in ordinary bacteria; moreover, 

 the formation of a true aseptate mycelium closely resembles 

 Mucor, an analogy rendered closer when we reflect that the 

 spores of B. anthracis are really chlamydospores. 



