56 H. B. FANTHAM. 
probably through forms like T. ziemanni, and on the other 
hand with the Bacteria through forms lke the Spirilla in 
which Swellengrebel (10) says there is a periplastic appendix. 
However, this classification is perhaps a little premature, for 
probably enough is not yet known of Spirochetes, and other 
allied organisms which might be included therein, to warrant 
the institution of such a class at the moment. Considering 
the present state of our knowledge, then, one must hesitate 
to push matters further. 
The characters which could be cited for distinguishing 
such a class are: 
(a) Elongate, thread-like body. 
(b) The presence of a membrane—the so-called “ undula- 
ting ”? membrane. 
(c) The absence of flagella. 
(d) The flexibility of the body, which is bounded by some- 
what soft (compared with Spirillum), yet definite, periplast. 
The body is not contractile, since it retains its dimensions, 
that is, there is a constant ratio between its length and 
breadth. 
(e) The ends may be rounded or prolonged into a stiff 
process. This last characteristic concerning the ends is 
variable, but in the type species 8S. plicatilis the ends are 
rounded. 
(f) The occurrence of longitudinal division. 
(g) The presence of a probable chitinoid substance in the 
periplast. 
(h) The nucleus consists of a spiral filament, on which are 
arranged transverse bars or rodlets of deeply staining 
chromatin. 
Schaudinn (21), in 1905, discovered the presence of an 
undulating membrane in the type species, and emphasised 
this as a characteristic of the genus Spirocheta. 
The question of the difference between pointed ends and 
flagella is rather a fine one, but is decided on the grounds of 
the stiffness and lack of motility of a process, and the pos- 
session of flexibility and motility by a flagellum. 
