THE SPIROCHETES 159 



middle, which they regard as a nucleus, poor in chromatin- 

 They also consider that this organism possesses a Trypanosome 

 phase (T. hits), with a flagellar border and a "centrosome" 

 granule, and they bring forward certain observations in support 

 of the occurrence of sexual forms and conjugation. No internal, 

 spiral, chromatin body has been described as yet in Treponema 

 pallidum, and it does not appear to belong strictly to the genus 

 Spirochceta. Many other short papers have been written 

 concerning Treponema pallidum, but little of its life-history 

 is known with certainty. It would therefore seem inadvisable 

 or at least premature, to discuss this organism any further. 



5. pertenuis (Castellani), from "yaws" or " frambcesia," 

 is another spirochaetiform organism of doubtful systematic 

 position. 



On the whole, the protozoal characteristics of the Spirochetes 

 seem to preponderate over the bacterial, and the present writer 

 inclines to the view that they are lowly forms of Protozoa, 1 for 

 which a new (fifth) class may have to be founded, when our 

 knowledge of these very interesting organisms is fuller. At 

 present one can only definitely state that they are Protists. 



To summarise : the Spirochetes are characterised by a long, 

 thread-like body, a membrane, the absence of true flagella, 

 flexibility of the body, the ends of the body being either 

 rounded or prolonged into a stiff process, the nucleus con- 

 sisting of a spiral filament, the occurrence of longitudinal 

 division, and the presence of a probable chitinoid substance 

 in the boundary layer or periplast. These characters might 

 be cited for distinguishing such a fifth (Spirochaetacean) class 

 of the Protozoa ; but, considering the present state of our 

 knowledge, one must not push matters. Classification only 

 marks the state of knowledge for the time being, and arbitrary 

 boundaries, marked off by hard and fast lines, are not usually 

 found in nature. 



Before concluding, a suggestion might be put forward as 

 to the significance of the chromatin apparatus of the Spirochetes 

 and its relation to the condensed form of nucleus found in most 

 Protozoa and in the typical metazoan cell. Robertson (8), 



1 Since the above was written, Krzystalowicz and Siedlecki have published 

 a further memoir on Spirochceta pallida, at the end of which they suggest that 

 the Spirochetes should be placed in a distinct section of the Mastigophora, for 

 which they propose the name Spirillofiagellata (vide Bull.' Acad. Sci. Cracovie, 

 1908, No. 3, p. 231). 



