CHAPTER II. 



BACTERIA AND THEIR PLACE IN NATURE. 



Bacteria. Bacteria are minute unicellular, living or- 

 ganisms generally accepted as belonging to the vegetable 

 kingdom.* They are placed among the lowest of the Thal- 

 lophytes. Naegeli called them "fission fungi" or Schizo- 

 mycetes, because they usually reproduce by transverse divi- 

 sion or fission. Under favorable conditions they mul- 

 tiply very rapidly. Bacteria do not possess chlor- 

 ophyl. Their structure seems to be very simple but their 

 functional activities are exceedingly varied. Although 

 microscopic, they differ in size, form and properties to such 

 an extent that several families, many genera, and hundreds 

 of species have already been recognized and described. The 

 part of biology which deals with the distribution, morpho- 



* The relation of bacteria to the animal kingdom on one side 

 and to the vegetable kingdom on the other has been contested by 

 several workers. The question is often asked, Are bacteria animals 

 or plants? As Fischer has so admirably pointed out, "The terms 

 'animal' and 'plant' are collective terms invented by laymen to de- 

 scribe familiar living things, insects and elephants, mosses and oak 

 trees, and they date from a time when such minute beings as bac- 

 teria were quite unknown. It is therefore as superfluous as it is 

 futile to attempt, as many have done, to detect the distinguishing 

 characters of the 'animal' and the 'vegetable' kingdoms among or- 

 ganisms for which these terms were never intended. For this rea- 

 son Haeckel and others have proposed to establish a third domain, 

 that of the Protista, which shall include all those forms in which 

 differentiation has not been pronounced on the lines of either animal 

 or plant development. The new group would take up Radiolarians, 

 Flagellata, and Infusoria from the animal side, and the Cyanophy- 

 ceae as well as some low forms of Algae and Fungi from the plants. 

 The border line between protista on the one hand and plants and 

 animals on the other, is, it must be confessed, artificial. To these 

 protista, which embrace approximately all those forms of life we 

 commonly call microorganisms or microbes, the bacteria belong." 



