704 



LEPTOTRICHE^J AND CLADOTRICHE^E. 



tivating this microorganism in artificial media. It is aerobic. Genuine 

 spore formation has not been demonstrated. 



The BEGGIA.TOA are distinguished by the presence of grains of sulphur in 

 the vegetative cells; these are seen as highly refractive granules with a 

 dark contour. They are widely distributed, and are found both in salt and 

 fresh water containing decomposing animal or vegetable material ; in sul- 

 phurous waters they are especially abundant, and accumulate upon the 

 muddy bottom, or upon organic substances undergoing decomposition, as a 

 milk-white, gray, pink, or purple layer; the bottom of ponds or of small 

 bays is often colored red by an extended and abundant growth of these wa- 

 ter bacteria. Meyer has shown that they are able to decompose sulphate of 



FIG. 255. Fjo> 256. 



FIG. 255. CrenothrixKuhniana; a-e, cocci in various stages of division; /, zooglcea of cocci 

 (X 400); g, zoogloea of various forms (natural size); h, colony of short filaments, composed of 

 rod-shaped cells, and developed from a group of cocci; i-r, filamentous forms, partly spirally bent 

 and of different thicknesses. (Zopf .) 



FIG. 256.-Beggiatoa alba (x 400); a and 6, filaments having an evident difference between 

 base and extremity, being segmented and free from sulphur grains below; 2-5, fragments of 

 filaments of various thicknesses and containing a greater or less number of sulphur grains; 6-8, 

 filaments stained with methyl violet, showing segmentation into rods and cocci-like elements; 9, 

 cocci; 10, development of a rod, c, from a coccus, a (X 600). (Zopf.) 



soda in organic solutions suitable for their growth. Like the previously de- 

 scribed genus (Crenothrix), spherical, rod-shaped, filamentous, and spiral 

 forms are included in the life history of the species. The filaments show a 

 differentiation as to base and free, growing extremity, but, unlike the Creno- 

 thrix, the segments into which the filaments divide are not included in an 

 external sheath. The filaments are flexible and exhibit a gliding movement; 



