267 
OBSERVATIONS ON THE DIVISION 
OF SPIROCHAETES. 
By DORIS L. MACKINNON, B.Sc. 
(From the Quick Laboratory, Cambridge.) 
2 Text-figures. 
The morphology of the spirochaetes has proved in recent years a 
fruitful source of controversy. One has only to look through some 
of the vast literature on the subject to be convinced that the time 
has not yet come for drawing final conclusions, so varied and so 
contradictory are the observations by different well-accredited authors. 
Concerning even such an elementary point as the mode of division, 
opinion is far from unanimous. In the well-worn dispute—are the 
spirochaetes protozoa or bacteria ?—the supporters of the former view 
have almost all maintained that the division is longitudinal, while their 
opponents have as strongly insisted that it is transverse. One may be 
inclined to doubt whether the mere direction of division is really a point 
of very great value in such a discussion: as Schellack (1907) has 
recently pointed out, bacteria never divide by simple constriction as in 
all hitherto described cases of transverse division in spirochaetes 1 . 
Furthermore, it may be well to remember that transverse division is 
not the peculiar property of the bacteria but occurs among certain 
groups of protozoa also. 
But apart altogether from systematic considerations, it is of interest 
to determine the mode of division in this group of organisms. 
It was suggested to me that it would be useful to compile com¬ 
parative summaries of the opinions of various observers on certain 
1 Swellengrebel (1907) described the formation of a sort of cell-wall between the dividing 
halves of S. balbianii just as in a bacterium—his observation has so far received no con¬ 
firmation. 
