256 Ellis . — The Life-history of Bacillus hirtus. 
vegetative cell soon protrudes and divides to form a two-celled individual. 
Immediately after germination one-celled and two-celled individuals are 
almost exclusively found. 
Motility commences very soon after germination and persists till the 
cytoplasm is removed by the act of forming spores. 
On Nutrient-Agar after fifteen hours is found a uniform lightish- 
grey growth, extending either after this period or at furthest after twenty- 
four hours over the surface of the condensed water. In the healthy 
condition, when consisting only of one-celled and two-celled individuals, the 
length varies from 2*5 [x to 4 \x and the breadth is almost uniformly about 
1-25 j jl (Fig. 21), but later the cells usually become somewhat longer, up to 
about 8 [x (Fig. 22). The breadth remains the same in all stages of growth. 
Normally spore-formation commences after three days. 
Gelatine plate cultures. Colonies first make their appearance as minute 
grey specks. Sooner or later the gelatine is liquefied. The colonies, 
however, often show stratification with a £ nucleus ’ at the centre, and some- 
times exhibit zig-zag outgrowths from the surface. 
Agar-plate cultures . Whitish colonies appear on the surface after 
twenty-four hours, sometimes in less time. The colonies may reach a 
diameter of 2-2 i m.m. in twenty-four hours, or may have spread over the 
whole surface of the Agar-plate. Sometimes the Agar gives the appear- 
ance as if it were partially liquefied. Occasionally the culture takes on a 
deep bronze colour. Formation of spores very plentiful. 
Gelatine-stab cultures. Growth appears as a light grey fleck on the 
surface of the gelatine. This grows larger, may or may not cover the whole 
surface of the gelatine. Gelatine is liquefied. When liquefaction takes 
place there is present a whitish-grey sediment at the bottom of the 
liquefied part. The liquid is yellowish-brown in colour and turbid. 
Growth in liquid media. Grows in the following liquid nutrient media. 
(See text.) 
O. Strong growth. Thick pellicle on surface. Strong acid reaction. 
Spore-formation postponed. 
I. Strong growth. Thick pellicle on surface. Strong acid reaction. 
Spore-formation postponed. 
III. Slightly weaker growth. Thick pellicle on surface. Gelatinous 
or mucinous precipitate. Strong alkaline reaction. 
VI. Weaker growth. Thin pellicle on surface. Acid reaction. 
