THE SPIROCHJETES 87 



though resembling the latter, and its reproduction 

 also differs. The chemical nature of the periplast is 

 not that of the bacteria. Lastly, the mode of trans- 

 mission by the agency of invertebrates is typical of 

 protozoal parasites, as the method of infection re- 

 sembling that of, say, a human subject with 5. duttoni 

 by Ornithodorus motibata, is apparently unknown for 

 bacterial diseases. The hereditary infection of suc- 

 cessive generations is also considered to be an argu- 

 ment in favour of the protozoal nature of the 

 spirochaetes. Thus the spirochaetes exhibit affinities 

 both with protozoa and with bacteria. They are, in 

 fact, intermediate to these two groups in many 

 respects, and are well termed border-line organisms 

 between animals and plants. In conclusion, we 

 think that the balance of evidence is somewhat in 

 favour of the inclusion of the spirochaetes among 

 the protozoa and of the adoption of the new class, 

 the Spirochaetacea, which was first set forth in 1907. 



