20 
Growth of Bacilli 
clean field, should be chosen. After a little experience it is generally 
easy to decide whether a given organism is going to divide or not. An 
organism which is likely to divide is usually larger and better defined 
and more opaque than one which is apparently dead. Moreover in 
some species the living healthy bacterium, if carefully watched, shows 
slight changes in outline at intervals, suggesting some plasticity in the 
bacterial walls. 
5. Method of recording the observations. 
After the preparation had been placed on the stage of the microscope 
and a suitable organism focussed, the time was recorded and the 
organism drawn and labelled 1. The specimen was then carefully 
watched, and any changes noted. Usually a long period of time, up to 
an hour or more, elapses before any change occurs. In most species 
the first important change to be seen is an increase in length, accompanied 
by a slight bending. Later a segmentation interval appears in the 
middle of the organism, dividing it into two more or less equal portions. 
These two parts are labelled 11 and 12 respectively in the drawings. 
After this division, or fission, the behaviour of the organism differs 
according to the group to which it belongs, but in all cases various 
movements take place to which the term “ post-fission movements ” was 
applied by Hill. The two new organisms (11 and 12) grow and again 
divide, and ultimately numerous organisms are produced and form a 
colony. For the purposes of identification the organisms arising from 
the division of 11 were labelled 111 and 112, and those from 12 were 
labelled 121 and 122 and so on 1 . 
The time at which each division or other well marked change 
occurred was also noted. 
6. Photographic records. 
Photographic records were also obtained, showing the mode of multi¬ 
plication of a typical member of each group. When a suitable bacterium 
had been found the microscope was removed from the thermostat and 
clamped in a horizontal position on a Zeiss camera. Illumination was 
obtained by means of limelight or a mercury vapour lamp, and the 
organism focussed on a clear glass screen. The magnification varied 
1 The genealogical relationships of the new cells are indicated by Hill’s (1901, p. 84) 
modification of Rickard’s (1901) system for culture record. The modification consists 
merely in omitting the decimal point and all figures to the left of the point. 
