180 



Marine Microbiology 



Fig. 1. Glass-columns filled with .saiul for model experiments. The inside 



of the glass tubes were covered with a thin water-repelling film of paraffin 



before filling with sand. Lateral openings allow samples to be taken from 



different levels. Both ends of the tube are closed and airproof. 



During 48 h, a suspension of 10^-10^ cells /ml of one species 

 in seawater and fresh water respectively passed through the 

 columns at a speed of 2 ml/min. Thereafter, the columns were 

 washed with sterile water ( seawater and fresh water respectively ) 

 at 1 ml/min during eight days. The number of living cells in the 

 dropping water was determined by plate cultm-e on nutrient 

 agar, at intervals, smaller at the beginning of the experi- 

 ment and greater later on. The first cells appeared within 

 the first minutes. Transportation through the sediment was 

 influenced by shape and size of the cells, by the type of the 

 sediment and by marine/limnic conditions. 



The influence of physical factors,— size of grains of the sedi- 



