186 STORRS AGRICULTURAL EXPERIMENT STATION. 
&. coli is very common in milk, as would be expected from the frequency of 
fecal contamination. The distinction between this and the last type is not 
sharp, and perhaps should not be recognized as marking separate types. The 
organisms which we have called aerocoli seem to be in a measure intermediate 
between aerogenes and coh, a fact further suggested by the study of some cul- 
tures sent me by Weigmann and labeled aerogenes. These were distinctly motile 
and peritrichic when studied by us, suggesting that either the presence of fla- 
gella has not always been regarded as diagnostic for separating coli and aero- 
genes, or that a non-flagellate type may later: develop flagelli. The typical 
characters of this group are as follows: 
B. coli communis. 
Morphology.—Size, 1v-1.6u x .4u-Iu. No chains, no spores, no capsules. 
Gram stain negative. Flagella peritrichic. : 
Gelatine colony.—A rather thin, spreading colony, umbonate, with a smooth 
center, granular edge, lobate. Litmus gelatine shows a dense white colony, 
which is decidedly acid, and may show gas bubbles. 
Gelatine sta#—A filiform needle growth, with a spreading, moderately thick 
surface growth. 
Agar streak,—Filiform, raised, smooth, sometimes lobate, opaque, white, 
moist. 
Fermentation tubes,—All three sugars are rendered acid and develop gas. 
They also show growth in closed arm. The amount of gas is somewhat varia- 
ble, and the proportion of hydrogen and carbon dioxide is approximately two 
to one, but quite variable. 
Bouillon.—An abundant turbidity, a sediment, and’ commonly a ring-formed 
pellicle. 
Milk.-—Is rendered acid and curdled. The curdling is not absolutely con- 
stant, however. Sometimes the milk does not curdle till after it is boiled. 
There is never any digestion, but a whey may separate from the curd. 
Potato.—A moderate, smooth, gray-white growth, sometimes luxuriant. 
Grows both at 20° and 37°, but better at 37°. Aerobic. Indol is produced. 
Variety A, Agrees with the type except that it fails to produce gas in sac- 
charose or lactose. 
Variety B. This differs from the typical coli chiefly in its action on milk, 
which it turns acid with a viscous coagulum. This is extremely slimy. Its 
colony is umbonate and tenacious, and can only be removed from the gelatine 
as awhole. In other respects it agrees with coli. Harrison regards it as 
aerogenes, but since it is motile, it must be grouped here, 
Ps. coi communis n. s. A gas-producing, non-liquefying Pseudomonas. 
This organism and two sub-varieties were all found in cheese made at this 
place. They are probably physiological varieties of the same organism. Vari- 
eties C and D came from the same colony and are interesting, therefore,. as 
showing a possibility of physiological variations from the same culture. 
Morphology.—Size, 1u-1.54 x .84-.94. No spores, no chains, no capsules; 
Gram stain negative. 
