D. L. Mackinnon 
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jerky, bat it did not change its position much. The thin portion 
became finer and liner, till its presence could scarcely be suspected, but 
for the simultaneous tugging movements of the separating halves. 
Finally the connecting thread broke, and the daughter-spirochaetes 
departed in different directions. 
6. A long spirochaete was seen, in which the two halves were 
separated by a finely drawn out middle portion. 
7. A spirochaete with a thinner median portion was observed for 
20 minutes. During that time the middle portion became longer and 
finer till scarcely visible. Death occurred before complete separation 
took place. 
8. A long spirochaete was noticed that showed very marked 
bending at a slightly narrower portion half-way along its body. This 
portion was watched thinning out till the connection between the 
daughter halves became scarcely perceptible: they died after 20 
minutes, and before they had completely separated. 
9. A long spirochaete with a weak central point was followed for 
about 10 minutes, during ’which time the median portion had thinned 
out considerably. 
10. A long spirochaete—about 14 curves—was followed for 30 
minutes. During that time the rather narrower median portion 
became still thinner, till the two halves were widely separated, though 
still attached by a fine protoplasmic bridge. At this point the spiro¬ 
chaete became gradually immobile and died. 
11. A long individual was kept in sight for about 25 minutes. 
Shortly after the beginning of the observation, a median thin portion 
became visible: division at this point went forward rather rapidly and 
the two halves separated. (Fig. 2 a, b, c, d, e, f.) 
Conclusions. 
In two cases apparent longitudinal division was seen in Spirochaeta 
recurrentis : in eleven cases the division was apparently transverse. It 
is not possible to say with absolute certainty, except in one instance, 
that these transverse divisions were not the final act in a longitudinal 
division. I am nevertheless inclined to think that both forms of division 
may take place , transverse being the more common. Breinl, and Dutton 
and Todd have expressed the same opinion with regard to S. duttoni, 
and Fantham also states that in S. balbianii both modes of division 
occur. 
