CHAPTER IV 



TAXONOMY (continued}. 



The Systematic Position of Bacteria; Other low Organisms with 



Pathogenic Properties. 



A QUESTION often asked is, whether bacteria are animals or plants'? 

 Now the terms ' animal ' and * plant ' are collective terms invented by 

 laymen to describe familiar living things, insects and elephants, mosses and 

 oak trees, and they date from a time when such minute beings as bacteria 

 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 ' vegetable ' kingdoms among organisms for which these terms were 

 never intended. For this reason 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 Cyano- 

 phyccae 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 micro- 

 organisms or microbes, the bacteria belong. 



Another question almost as common as the first is, whether bacteria are 

 fungi, as the synonym Schizomycetes or fission-fungi would seem to imply. 

 As far as the processes of life are concerned the bacteria and fungi agree 

 in every detail, for, with very few exceptions*, the members of both groups 

 are unable to derive their nourishment from inorganic compounds. That is 

 to say both bacteria and fungi arc mctatrop/iic, are restricted in their food 

 to substances fabricated by the higher organisms. Some of them arc even 



* The saltpetre bacteria and others. 

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