230 BACTERIA. 
tures. Before making fresh cultures, glasses were care- 
fully washed in hot water, and treated with a solution 
of corrosive sublimate. My knife and needle point were 
brought to ared heat, before cutting a potato or making 
an inoculation. Although this method does not always 
insure as pure cultures as the sterilized test-tubes 
plugged with cotton-wool, used in bacteriological labora- 
tories, it is a tolerably certain one, and it has the advan- 
tage of showing how one form may follow and overpower 
another. ; 
While engaged in this work, I took daily notes of the 
color, form, and texture of the zoogle@z as well as of 
their microscopic characters. Slides were frequently 
prepared. In these, the bacteria were stained with 
aniline violet and mounted in benzol balsam. The micro- 
scopical work was done with a Zeiss one-eighteenth 
homogeneous immersion objective, and an Abbé con- 
denser. 
The following is simply a réswmé of my observations : 
I have not ventured to give names to the forms for 
which I find no adequate description, but for the present 
will designate them as species a, b, c, etc. 
Micrococcus candidus, Cohn. I first met with this 
species in my Cambridge cultures, and it appeared 
quite frequently during my recent work. Its first ap- 
pearance was in very minute milky dots which in a short 
time became confluent in milk-white mammillated 
masses. These afterward became dry, dull, and chalky. 
Occasionally a growth was seen coming through a small 
break in the skin of the potato. This was very dry, 
light, and powdery, and presented an appearance much 
like the efflorescence of a salt. The growth of the 
zoogloea is never very rapid, but it is persistent and 
seldom yields its place to other forms, even though 
their growth may be much more luxuriant. The cells 
are readily stained, are quite large, and show interest- 
114: 
