THE BIOLOGIC RELATIONSHIPS OF THE BACTERIA

Discussions of the affinities of bacteria with other organisms, their phylogenetic relations to the higher plants and animals and the principles of classification within the group itself have often resulted in much uncertainty and difference of opinion. While it cannot be said that general agreement on these topics has yet been reached, there is no doubt that recent investigations into the physiology of bacteria have effectually disposed of some speculations once current. The position which bacteria occupy with reference to other groups of living organisms is to-day better defined than ever before.

The value of morphologic characters as a basis for determining bacterial relationships is evidently not so great as that of the physiologic manifestations of these organisms. This is so, notonly because external structural characters are not easily studied in organisms that lie close on the borders of invisibility, but because internal—that is, physiologic or, perhaps more exactly, chemical—qualities