THE SPIROCHETES 



i53 



progression may be compared with that of an eel, with the spiral 

 movement in addition. 



The structure of the membrane must now be mentioned in 

 some detail, and its relation to the mechanism of movement of 

 the organism. After appropriate staining, as by gentian violet, 

 iron haematoxylin, or Delafield's haematoxylin, this structure is 

 seen to be fibrillar in S. balbianii (fig. 2, a, c, d) and S. anodontce. 

 Modifications of the Romanowsky stain do not show this fibrillar 

 structure so clearly. Allowing for the spiral, sinuous character 

 of the membrane and parent organism, it is seen that these fibrils 

 are almost longitudinally arranged (fig. 2, a, d). It is necessary 

 to consider carefully the sinuosities and foldings of the mem- 

 brane in determining the direction of the fibrils, as they may 

 sometimes appear somewhat transverse (fig. 2, c). The fibrils 



numbr. 



periplast. 



chr masses. 



Fig. 3. — Diagrams of transverse sections of Spirochetes from an infected Lamellibranch 

 crystalline style. The membrane (jnembrS) is seen to be a lateral extension of the 

 periplast containing myonemes {my.), and a chromatic border. The membrane is 

 spirally wound, for a node of the membrane is passed through in c. (After Fantham.) 



are termed myonemes, and some of them also occur in the 

 periplast of the body of the organism. Two sets of myonemes 

 are seen in dividing forms (fig. 2, c, d). When the membrane is 

 closely contracted against the body, it may appear like a sheath 

 around it, as was once described for S. balbianii. However, it 

 is not a sheath, but a lateral outgrowth of the ectoplasmic 

 periplast, as is seen from a consideration of fig. 3. When 

 loose, the membrane is clearly seen to be spirally wound round 

 the body of the organisms (fig. 2, a, b, c, d), for its chromatic 

 border can be discerned in the troughs of the wave-like body 

 even under comparatively low powers. It is erroneous to state 

 that specimens of S. balbianii may occur devoid of a membrane. 

 Such specimens really possess a closely contracted membrane. 



