ON CEISTISPIIJA VEXEKIS NOV. SrEC. 53o 



C-ristispira aiul its allies, l)eing- flexible and not rigid 

 organisms, show affinities with the Protozoa and not witli the 

 Bacteria in consequence. I do not know who is responsible 

 for the original statement that all Bacteria are rigid organisms, 

 but it: is certain that sncli a statement cannot be accepted. 

 Many Bacteria of large size are flexible to a considerable 

 extent. I have shown this to be the case in Bacillns f lex i lis 

 (Dobell, 1908) and a number of allied forms (Dobell, 1910a). 

 It is therefore manifest that flexibility cannot be used as a 

 criterion for judging whether the Spirocha?ts are to be ranked 

 among Protozoa or Bacteria. 



Conjugation. — The organisms described as "gametes" 

 by Perrin and others, and the stages said by thetn to repre- 

 sent conjugation stages, are all quite arbitrarily so designated. 

 I believe there is absolutely not a vestige of evidence that 

 conjugation occurs in these organisms. Neither Swellen- 

 g'rebel, nor Schellack, nor Gross, nor myself could find any 

 indication of sexual plieuomena in this group. Both Schellack 

 and Gross have discussed the matter more fully, and I am in 

 complete agreement with their conclusions. 



Encystment. — AVhether Cristispirje encyst or not is a 

 point which is still undetermined. I believe the "cysts" 

 described by Perrin and others are really to be regarded as 

 the results of degeneration or plasmoptysis. Schellack and 

 Gross both appear to be of the same opinion. At all events, 

 it may be said with justice, I believe, that no clear case of 

 eucj'stment has yet been described in Cri sti spirte. 



Affinities and Classification. 



Having now briefly noted the more important features in 

 the structure and life-cycle of the Cristispirge, it is possible 

 to discuss the affinities and classification of these most 

 remarkable organisms. 



At the present moment it is customary to assemble under 

 the common name " Spirochsets " three different gi-oups of 

 unicellular organisms. These are (1) the Cri stispira?. 



