.662 CONTItlBUTIONS TO OUR KNOWLEDGE OF SOIL-FKRTlLrrV,vi., 



garden soil, liad been seeded into a bean-infusion, and, after a 

 time, a rich growth of ama'bsc was found. The suspension was 

 centrifugalised, and the sediment rapidly washed with 0-2% saline. 

 The amcebic were suspended in saline, a part of which was heated 

 for 10 minutes at 62° to 64°. To each 20 grm. portion of soil, 

 4 c.e. of suspension were added. This contained, in the case of the 

 unheated suspension, (5,089 living motile amoob^e, no motile ciliates, 

 many cysts, presumably of the lattei", and many bacteria. 



Experiment ii. — The Addition of Amceb.*;. 



The experiment was repeated and conlirmed at a later date, with 

 a poor sandy soil. The tests wei'e contained in small bottles closed 

 with wooden eoiks, tlu'ough which jiassed glass tubes furnished 

 with open capillary ends of approximately 1 mm. bore. The 

 evaporation from the soil was very small, the loss being equal to 

 only 0-37% in 73 days at 22°. Each test received four c.c. of a sus- 

 pension of Amoeba Umax in 0"2% saline. This quantity contained 

 2,720 moving and 800 encysted amoebae, together with a mixed 



pairs of bacteria cease their motion as the protozoal arm touches them, but 

 ill a few seconds they are as active as ever. I liave seen an amoeba, in 

 moving forwards, touch a rod-shaped microbe which adhered to the 

 surface, sliding over but still maintaining its position in the field, until 

 the terminal was readied. Tliere it remained attached. Meanwhile, 

 another microbe was similarly treated, but somehow became detached 

 from the terminal. In its circumambient wandering, the ama-ba touched 

 the same bacterium, and both became fixed to the terminal tuft of barely 

 visible slime, until a fragment of debris, encountered by the protozoon, 

 proved too weighty, and fragment and bacteria were left behind. Mouton 

 [Ann. de I'lnst. Past., xvi., p.476] seems to have seen, in this entangle- 

 ment, an agglutination of the microbes by an agglutinin secreted by the 

 pulsating vacuole. 



