BACIJLLUS CO LI CO MM UN IS. 397 should be important evidence of their separate individ- uality. The author has no doubt that the Bacillus coli cotn- munis is not a single species of bacteria, but is a name applied to a group whose individual differences are thus far too similar to enable us to differentiate them. This opinion seems to be shared by other bacteriologists, some of whom have attempted to separate the bacillus into groups, types, or families. In order to establish a type species of the Bacillus coli communis, Smith l says: "I would suggest that those forms be regarded as true to this species which grow on gelatin in the form of deli- cate, bluish, or more opaque, whitish expansions with irregular .margin, which are actively motile when exam- ined in the hanging drop from young surface-colonies taken from gelatin plates which coagulate milk within a few days; grow upon potato, either as a rich-pale "or brownish-yellow deposit, or merely as a glistening, barely recognizable layer, and which give a distinct indol reac- tion. Their behavior in the fermentation-tube must conform to the following scheme: ^Variety a: "One per cent, dextrose-bouillon (at 37° C.)- Total gas approximately *4; HCO2 approximately */L ; reaction strongly acid. "One per cent, lactose-bouillon: as in dextrose-bouil- lon (with slight variations). "One per cent, saccharose-bouillon; gas-production slower than the preceding, lasting from seven to four- teen days. Total gas about %\ HCO2 nearly %. The final reaction in the bulb may be slightly acid or alkaline, according to the rate of gas-production. "Variety $\ " The same in all respects, excepting as to its behavior in saccharose-bouillon; neither gas nor acids are formed in it" 1 American Journal of the Medical Sciences, 1895, no, p. 287.