Ward . — Some Thames Bacteria . 303 
4.30 the diffluent walls had softened and dissolved, and the 
imprisoned swarmers escaped, and were swimming about as 
actively as any of the other free rods. 
These observations were confirmed several times — as soon 
as the temperature rises to about 23-5 to 25 0 active swarming 
begins. 
In some cases a pair of recently divided rodlets behave 
in a peculiar manner, and this I have seen not once, but 
several times. Each is capable of movement on its own 
account, but in some cultures (gelatine) the newly-separated 
rodlets separate by backing away in a straight line, and then 
come together again, end on, and remain a few seconds as 
if they had never separated at all Thus, in Fig. 13 I have 
sketched the relative positions of one of these pairs at four 
stages of their oscillations. At first they Were closely applied 
pole to pole in a straight line ( a ), then they suddenly darted 
asunder ( b ), till separated by about three times the length 
of either : after a few seconds they flew together again 
(< c ), and then again flew apart ( d ) ; and this went on for at 
least half an hour. 
It is quite a common event to find the rodlets swarming 
in this way, though the pairs do not invariably approach 
and recede in the same straight line. It was noticed that 
in one and the same case the movements in either direction — 
separation or flying together — might concern both, or only 
one, or sometimes one and sometimes the other, and by no 
means equally. If we call the rodlets A and B, sometimes 
they darted apart five or six times the length, equally distant 
from the point where their poles joined, and next time 
A would dart off and leave B quiescent, or A would move 
twice or three times as far as B : similarly on darting together. 
I could find no rhythm about this phenomenon, and do not 
understand its meaning. At one time I thought the darting 
together might be due to an elastic cilium which they were 
tugging at, but it seems improbable. 
In most cases, however, the swarming is in and out 
irregularly when several are concerned, and it seems to 
