706 LEPTOTRICHE.E AND CLADOTRICHEJE. 



berg (Spirillum sanguineum, No. 416). The red pigment produced by this 

 species is known as bacterio-purpurin. It is insoluble in water, alcohol, 

 chloroform, ammonia, or acetic acid, and is changed by hot alcohol into a 

 brown, and by chloroform into an orange-brown, substance. 



435. BEGGIATOA MIRABILIS (Colin). 



Found in sea water, upon the surface of putrefying animal and vegetable 

 substances, as a white layer; common upon the coasts of Denmark and Nor- 

 way (Warming). 



^Morphology. This species is distinguished by the considerable thickness 

 of the filaments, which may be as much as 30 n ; these undergo segmenta- 

 tion into cylindrical masses, which again break up into thin discs, and these 

 are supposed to divide into cocci-like elements such as Zopf has described in 

 the other species of this genus. The complete life history of this species has 

 not been determined. Like the other species described, the cells contain 

 granules of sulphur. 



436. PHRAGMIDIOTHRIX MULTISEPTATA (Engler). 



Found in sea water, attached to crabs 



Morphology. Filaments from 3 to 6 jit in diameter, made up of thin disc- 

 like segments, the diameter of which is four to six times less than the thick- 

 ness; these cylindrical segments undergo segmentation into halves and 

 quadrants, and finally into still smaller fragments which become rounded 

 and resemble cocci ; these probably are set free, but this has not been ob- 

 served; apparently they grow out first into very thin filaments which subse- 

 quently increase in diameter. The genus to which this species belongs is 

 distinguished from Beggiatoa by the absence of sulphur grains, and from 

 Crenothrix by the fact that the segments are not enveloped in an exterior 

 sheath, as well as by the comparative thinness of the cylindrical segments. 



LEPTOTHRIX BUCCALIS. According to Zopf, the leptothrix so common in 

 the human mouth presents the same variety of forms as has been ascribed 

 to the Beggiatoa and Crenothrix. We cannot accept this as established, and 

 have described Leptothrix buccalis among the bacilli (No. 395). "Vignal 

 claims to have cultivated this species, but, in view of the failure of Miller and 

 others to obtain it in cultures, it appears doubtful whether the microorganism 

 described by him under this name corresponds with the Leptothrix buccalis 

 of Robin (see page 683). 



437. CLADOTHRIX DICHOTOMA (Cohn). 



Found in stagnant and running water very common. It is frequently 

 associated with Beggiatoa and is common in the refuse water of factories, 

 especially of sugar factories. In Russia it is often found in abundance in the 

 water supply of towns. It may readily be obtained from the surface of pu- 

 trefying algae or animal substances immersed in river or swamp water. 



Morphology. According to Zopf, the cocci-like reproductive elements 



grow out into rods, and these into fine filaments, from which later pseudo- 

 ranches are given off. This apparent branching of the filaments is the dis- 

 tinguishing generic character of Cladothrix. Under a sufficiently high 

 power the branched appearance is seen not to be a true dichotomous ramifica- 

 tion, but to result from the growing out in a lateral direction of a detached 

 segment. These long filaments break up again into long rods, these into 

 shorter rods, and finally into cocci. The sheath of the filaments is often col- 

 ored yellow, rusty-red, olive-green, or dark-brown by oxide of iron. The 

 segments are forced from the free extremity of the common sheath by the 



