2IO SULPHUR BACTERIA 



riibruni is sensitive to sodium chloride, and also to ammonium 

 chloride. But if, in Pfeffcr's experiment, the water in the 

 capillary tube contains both i/iOO sodium chloride and l/iOO 

 ammonium chloride, and if the bacterial suspension outside 

 the capillary tube contains l/iOO sodium chloride, there is no 

 attraction. The presence of sodium chloride has destroyed 

 the efficacy of ammonium chloride. Similarly ammonium 

 chloride neutralizes the efficacy of sodium chloride. The same 

 held true for other combinations of salts, for example, potassium 

 sulphate and ammonium sulphate. 



Buder's Researches. 



[a] Ciliary Movements of the Sulphur Bacteria. — -Very 

 interesting results were obtained by this investigator in 



Fig. 56. — Positions of the cilium of a spirillum moving forward with the 

 ciliiim attached behind. For explanation see text. 



his examination of the cilia and the movements of Thio- 

 spirilhmi jenense (see p. 161), and a species of Chromatium. 

 Buder found that the single cilium shows a rotary movement. 

 The positions of the cilium when the organism is moving 

 forward with the cilium behind are shown in Fig. 56. 



The shaded parts show a section of the space enclosed 

 during the revolution of the cilium. It will be seen from the 

 diagram (Fig. 56) that the shape of this space is, during move- 

 ment, continuously undergoing alteration, and that the 

 alteration takes place in a definite order. In No. 4 of the series 

 the cilium is rotating almost at right angles to the spirillum. 

 This is the position which it assumes prior to that indicated in 



