THE IRON-BACTERIA 385 



more polar cilia. In a very exceptional case the writer has 

 observed these detached fragments assuming the form of spiral 

 threads after leaving the parent organism. Each fragment 

 was made up of a few rods enclosed in a common sheath. 

 Motility was effected by means of polar cilia, the fragments 

 also assuming a wavy structure (fig. 7, C). Without the use 

 of stains they could not have been distinguished from members 

 of the Spirillaceae. A still more remarkable occurrence in the 

 same culture was the lateral detachment of single rods, which 

 on liberation assumed a spiral form with cilia at both ends, 

 and swam off in the true spirillum manner (fig. 7, A). The 

 detachment of spiral fragments from Cladothrix threads was 

 noted by Zopf more than thirty years ago, but subsequent 

 observers have either ignored his announcement or doubted its 

 accuracy. These phenomena were observed in one, and only 

 in one, culture out of an extensive series of observations carried 

 out by the writer, and extending over eighteen months. The 

 theoretical importance of this fact is great, for it shows that 

 one and the same organism can produce both the bacillus and 

 the spirillum forms of bacteria, which at present are regarded as 

 being fundamentally distinct. A closer examination of the 

 rods with the help of staining reagents reveals a delicate, well- 

 defined membrane. In well-nourished cultures each cell has 

 granular contents. Further, the presence of oil and glycogen 

 can be demonstrated. As regards division, that process is 

 essentially the same as in the genus Bacillus. A delicate trans- 

 verse membrane is thrown across, this is followed by constric- 

 tion, with eventually the separation of the rod into two cells. 

 Each then grows until the mature form is reached. The dis- 

 tribution of this organism is very wide. As will be seen in the 

 discussion of the physiology of the Iron-bacteria, it is only 

 incidentally a member of the Iron-bacteria, for it is found in 

 many non-ferruginous waters where there is a slight organic 

 decomposition. Further, there can be little doubt that what 

 we call Cladothrix dichotoma is either a group of very closely 

 related species or else is one species capable of much pleo- 

 morphism in adjustment to the varied conditions of life. 



Clonothrix fusca (Schorler) 



The discovery of this organism by Schorler in the water- 

 works of Dresden added another member to the group of Iron- 



