68 STORRS AGRICULTURAL EXPERIMENT STATION. 
while Groups I. and II. include the anaerobic or facultative 
anaerobic bacteria, that grow very scantily upon the surfaces of 
media. | 
Frequently acid colonies are found that seem to belong to 
none of these three groups. This is due sometimes to species 
different from any of those above mentioned; but more com- 
monly it is attributable to the fact that some colonies do not 
show their typical characters. This is especially the case when, 
because of liquefiers, the plates must be studied before they are 
old enough. ‘his lack of differentiation of course introduces 
an error in the results. In our tables these colonies are in- 
cluded in the column headed acid, species undetermined. Most 
of the bacteria there listed would be properly placed in Groups 
I., II., or III., if a perfect differentiation had been possible, 
although some probably belong to Group V., and some perhaps 
belong elsewhere. 
Group IV. Streptococcus group. ‘This group is less sharply 
differentiated and is in general of a neutral character as relates 
to milk. It includes colonies with no particular characteristic. 
They are never acid and rarely alkaline in reaction; they are 
commonly rather opaque, small, round colonies while under 
the surface of the gelatin, but may spread over the surface to 
form a white colony a millimeter in diameter. They are separ- 
ated from others in the study of the gelatin plates by lacking 
any distinctive characteristics; and it is to be suspected, there- 
fore, that they comprise a number of species. We have 
isolated and studied a large number of the colonies tabulated 
in this column from many different samples of milk, and have 
thus far found them to consist of four species of milk bacteria. 
Of these the majority are streptococci, from which we have named 
the group, No. 229. Some of them are bacilli agreeing with 
the streptococci in most of their characteristics—No. 194. A 
third species is a rare fluorescent, bacillus No. 90, while Nos. 
205 and 224 of our list are occasionally grouped here. Although 
this group is, then, a miscellaneous collection, the colonies are 
all neutral in their action. None of them produces any visible 
effect on milk; none of them produces enzymes; and none of 
them produces any signs of putrefaction. So far as we have 
been able to determine, they are of no significance in the milk, 
Experiments not here reported have shown us that they come 

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