On the Growth of certain Fresh-ivater and Soil Protista. 165 



The ease with which Prowazekia can be grown in culture media containing 

 tyrosin suggests the possibility of investigating its distribution in various 

 types of soil. Experiments in this direction are at present very incomplete, 

 but as far as they go they tend to show that rich manure soil or leaf mould 

 contains a considerably greater number of the minute flagellates than less 

 rich soils. This is well seen in Table II. (Compare ISTos. 4-9 with 

 ISTos. 10-15.) 



In summing up the points observed in the cultures of soil flagellates we 

 notice the following facts : — 



(a) As compared with Euglena they are able to live in cultures to which 

 organic compounds of very varying natures have been added. 



(b) This comparative impartiality is the result of the holozoic mode of 

 nutrition, the development of the flagellates being absolutely dependent on 

 the bacterial growth. 



(c) The presence of the Miquel salts in the solution is necessary for the 

 growth of the soil flagellates and for the proper development of the bacteria 

 upon which they feed. 



(d) The flagellates can feed upon a variety of different types of bacteria. 



DESCRIPTION OF PLATE. 

 Soil Flagellates from a Culture containing a Mixed Bacterial Flora, showing 

 various Types of Ingested Bacteria, x 2000. 



Figs. 1-2. — Two individuals containing ingested bacilli. 

 „ 3-6. — Individuals containing cocci of two kinds. 

 „ 7-8. — Two individuals containing partially digested bacteria. 



