Ward— A Violet Bacillus from the Thames . 63 
in the liquid itself flecks of white and violet colonies were 
floating or sunk to the bottom (Fig. 8). In three or four 
months all the gelatine is liquefied, and dirty-violet flecks are 
floating in the liquid 
Closer examination shows that the violet- mass is composed 
of a complex folded and wrinkled zoogloea-form, and that the 
pigment is confined entirely to this, and does not diffuse into 
the liquefied gelatine in which the trembling jelly-like mass 
floats. These zoogloea-masses are found scooping out 
cavities in the otherwise solid gelatine, and lining them with 
the folded membrane. Later on, the liquefaction slowly 
spreads away from the zoogloea, but the pigment is confined 
to the latter. The same occurs, somewhat more rapidly, at 
20 0 C. On removing the zoogloea-membrane, these cavities 
are left apparently devoid of Bacilli ; but the microscope 
shows their presence in abundance, and in a few days those 
remaining have multiplied and again covered the concave 
surfaces with the membrane, which soon thickens, wrinkles, 
and obtains the violet colour as before. When the gelatine is 
completely liquefied, the violet colour is confined to the 
membrane at the surface, or to pieces of it which sink in : 
the non-oxygenated submerged Bacilli forming a precipitate 
at the bottom are buff or greyish-yellow, or even dirty-white. 
On agar, at 20° C., a thick white or slightly buff opaque 
streak forms in twenty-four hours or so, and in three days has 
a waxy appearance, often with raised margins. On the fourth 
day the purple colour begins to show here and there in the 
white, and in ten days the whole surface of the agar may be 
covered with an intensely deep purple, corrugated membrane, 
which is very tough and may be lifted off bodily from the 
medium. Underneath, the growth is still white, and the 
colour is confined to the zoogloea-mass — it never diffuses into 
the agar (Fig. 9). In feeble cultures the growth may be so 
slow as scarcely to extend beyond the path traced by the 
inoculating needle ; but here too, the deep, ink-like, purple- 
black drops soon appear as before. 
On potatoes, at 20°C. ; a thickish, dirty-white streak, tinged 
