ISABEL MULFORD. 235 
At first the zoogloea has scarcely more coherence than 
water, but in a short time it becomes so viscid that it 
may be drawn out in delicate threads more than half a 
metre in length. Prof. Trelease says that it makes a 
very adhesive paste. 
These changes follow one another in rapid succession. 
In about two weeks from its first appearance, the folds 
of the surface disappear, and the mass becomes some- 
what deliquescent and glistening ; not infrequently it 
flows in a thick stream over the sides of the culture. 
Under the microscope, this gelatinous mass is seen to 
be filled with rod-like cells, which are sometimes isola- 
ted, sometimes united in short filaments. A delicate 
cell-wall has been demonstrated. These cells have the 
power of motion when placed in water, but flagella 
have not been seen. The measurements are 1.6-7 by 
6-8. 
Bacterium aurantiacum, Trelease. In my cultures of 
last year, B. aurantiacum was one of the first species 
to attract my attention. At first appearing as a light 
yellow film, the zooglwa gradually increases in thick- 
ness and consistence until it has a smooth, wavy ap- 
pearance and a bright, orange color. This color is 
maintained for some time, but the old zoogl@e change 
to a dull, dark brown. The cells are single or con- 
nected in chains. They have arapid motion. The old 
cells often have a condensation of protoplasm at either 
end. In size they are considerably smaller than those 
of B. candidum ; they measure 1-2u by .4-.5u4. The 
cells are not readily stained by the ordinary violet fluid. 
Bacterium luteum, Trelease. This also is a very com- 
mon and avery persistent species. Itsfirst appearance 
is quite similar tothat of B. aurantiacum. The zooglaa 
is semi-fluid, and though at the very beginning of 
erowth it is nearly transparent, it soon shows a light 
yellow coloration. 
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