x.] BACILLUS. 113 



occurs in pond-water containing decomposing organic matter. 

 It consists of long whitish threads fixed on chlorophyll -con- 

 taining algae. The threads when fresh appear smooth, pale, 

 occasionally granular, and on staining they are seen to be 

 composed of shorter or longer bacilli just like the leptothrix 

 form of bacillus subtilis ; but they are thicker than the 

 bacillus subtilis. Occasionally the ends of the threads are 

 seen not as linear series of bacillar rods, but like bacillus 

 anthracis and the bacillus of blue milk (see below) as 

 chains of torula-like spherical elements. From the threads 

 single motile bacilli are seen to come off. The threads are 

 only apparently branched, since the branches are threads 

 merely stuck on to other threads sideways at an acute angle. 

 A bacillus may be seen to stick to a thread and then to grow 

 out by continuous divisions into a long chain of bacilli, thus 

 forming, as it were, a side-branch. Some of the threads are 

 wavy and curved; most of them are, however, straight. 

 Zopf 1 claims to have observed that the threads of the 

 cladothrix gave rise to micrococcus, bacterium, bacillus, and 

 spirillum ; and states that each of these is again capable of 

 growing into the threads of the cladothrix. But these 

 observations were not made after exact methods. 



(e) Beggiatoa. In stagnant water, particularly in sulphur- 

 containing water, peculiar oscillating colourless threads are 

 met with of the thickness of o'oooi to 0-016 mm.; they 

 contain highly refractive granules, which Cohn (Beitrdge zur 

 Biol. d. Pfl. i. 3) has shown to be composed of sulphur. 

 After dissolving these granules it is seen that each thread is 

 septate, being composed of a sheath and transverse septa at 

 regular intervals, by which the threads appear made up of a 



1 Zur Morphologic der Spaltpfianzen^ Leipzig, 1882 ; see also 

 Cienkowski. 



