538 C. CLIFFOIM) nOP.KLF,. 



But the same might be said of many other Protista. Two 

 most important charactei's of the Bacteria — the formation of 

 endospores and the possession of fiagella — are not encountered 

 in the Spiroch^ets. The structure of the cell, especially as 

 regards the nucleus, in Cristispira and Spirochasta is 

 ([uite different from that of Spirilla. With regard to the 

 latter, I would refer the reader to my work on the cytology 

 of the Bacteria (Dobell, 1910a). There is, in fact, no real 

 reason for regarding Spirochfets as Bacteria, 



There seems to be a curious tendency on the part of many 

 workers to reason thus : Spirocliasts are not Protozoa, there- 

 fore they are Bacteria; or conversely, they are not Bacteria, 

 therefore they are Protozoa. The premisses are both correct, 

 I believe, but the deductions are both wrong. Spirochaits 

 are neither Protozoa nor Bacteria ; they are a group of Protista 

 which stands alone. They certainly have a few characters in 

 connnon with Bacteria, but the differences greatly outweigh 

 these. 



In conclusion, I will summarise the results to which my 

 work has led me. They are as follows : 



The organisms commonly called Spirocha?ts may be con- 

 veniently collected into a single group, for which I propose 

 the name Spiroch^toidea. This group comprises three 

 different sets of forms, which may be correspondingly classified 

 in three different genera — Spirochasta, Treponema, 

 Cristispira. These three groups of organisms, whilst 

 showing certain resemblances to one another, possess no 

 definite relations with Protozoa, Bacteria, or Cyanophycea). 

 The Spirocha3toidea should therefore be regarded — for the 

 present — as a group of Protista which stands apart. 



Imperial College of Science and 

 Technology, London. 

 Novemher, 191(1. 



