MORPHOLOGY OF THE GENUS BEGGIATOA 279 



said gas, which is indispensable to its continued existence, then the threads 

 begin to break up (Fig. 71), the contents except a thin coating attached to the 

 walls vanish, and they finally perish. No success has attended the search for 

 spore formation in the Beggiatoa. The most abundant species of this genus is 

 Beggiatoa alba, the threads of which are 2.8-2.9 (j. in thickness, whilst the length 

 of the individual members varies between 2.9 and 5.8 p, the shortest of them 

 being thus symmetrical. A second species, with a diameter of 1.6-1.7 /*, the 

 length of the separate cells being 4-8.5 /.i, has been named Beyglatoa media ; and 



. 



FIG. 71. Beggiatoa alba. 



Moribiind through lack of H 2 S. Thread falling 

 apart into its short members, which thereupon 

 assume a rounded form. Magn. 900. (After 

 Winogradsky.) 



FIG. 70. Beggiotoa alba. 



The same portion of thread under different 



conditions of existence. 



. in a medium rich in H 2 S ; the thread is densely 

 packed with sulphur granules ; b. after twenty- 

 four hours' sojourn in a liquid devoid of HgS ; 

 only a few sulphur granules remain ; c. at the 

 end of a further forty-eight hours ; sulphur 

 totally disappeared, transverse walls now visible, 

 contents of individual cells granulated. Magn. 

 900. (After W'inofjradsky.) 



FIG. 72. Terminal portion of ihreads of (x) 

 Beggiatoa media and (y) B. minima. 

 Magn. 900. (After Winogradsky.) 



a third kind, whose diameter is only 0.8 p, is called Beggiatoa 'minima. Both 

 these species are shown in Fig. 72, magnified to the same extent as the first- 

 named species. In addition to these there is still a large number of species 

 whose threads vary in diameter between the above limits. Compared with all 

 these the Beggiatoa mirabilis noted by COHN (XII.), Warming, and Engler, but 

 not yet more minutely examined, the threads of which are said to attain a 

 breadth of 30 p, is gigantic. According to Winogradsky, the breadth of the cells 

 of any given species is to emphasise this point once more unalterable. 



The growth of these Schizomycetes is very slow, a thread requiring at least 

 twenty-four hours to double its length. They are extremely susceptible, even 

 merely the grip of the forceps being fatal. For this reason they have to be 

 sucked up by means of a small tube, for purposes of examination, and protected 

 from the pressure of the cover-glass by introducing splinters of glass, &c., into 

 the liquid. 



