2 Lectures on Bacteria. [ i. 



harm they occasion, that is, we must study their vital processes 

 and the effects which these produce on the objects outside of 

 themselves. 



We begin with the first question, and we will first of all bestow 

 a moment's consideration on the name. 



Bacteria, meaning rod-shaped animalcules or plantlets, from 

 the rod-like form which many of them exhibit, are also termed 

 Fission-fungi or Schizomycetes. The two expressions are not, 

 strictly speaking, of the same import. 



The reason of this is that the word Fungi is used in two 

 senses. In the one it is the name for those lower flowerless 

 plants which are devoid of chlorophyll, the green colouring 

 matter of leaves, and hence exhibit certain definite peculi- 

 arities in the process of their nutrition. We shall speak of 

 these peculiarities at greater length in succeeding lectures; 

 at present we will only make the preliminary observation, 

 that all organisms devoid of chlorophyll require already formed 

 organic carbon-compounds for their nutrition, and cannot obtain 

 the necessary supplies of carbon from the carbon dioxide which 

 finds access to them. The construction of organic compounds 

 from this substance is bound up with the presence of chlorophyll 

 and analogous bodies. 



Fungi in this sense are therefore a group characterised by 

 definite physiological peculiarities the mark of which is the 

 absence of chlorophyll, somewhat in the same way as birds and 

 bats may be grouped together under the head of winged 

 creatures. 



In the other sense, that of descriptive taxonomic natural 

 history, the term Fungi denotes a group of lower plant-forms 

 distinguished by definite characteristics of structure and develop- 

 ment, and recognised at once when we see a mushroom or a 

 mould. The members of this group are all as a matter of fact 

 devoid of chlorophyll, but they might contain chlorophyll and 

 yet belong to this group, just as a bird may have no apparatus 

 for flight and yet be allowed to be a bird. To these Fungi, as 



