Distribution and Function of Marine Bacteria 41 



in the food chain, microorganisms-neieids-fisli. Tlie application of 

 the author's submerged shde method wliich allows one, as it 

 were, to descend with a microscope to the required depths, has 

 revealed organisms previously unknown. Electron microscope 

 studies suggest that ultramiscroscopic non-cellular forms of life 

 exist in the seas and oceans. 



The second paper was given by Dr. Shewan ( Chapter 47 ) of 

 the Torrey Research Laboratory on the troublesome question of 

 how to separate marine genera of Pseudomonas, Achromohacter, 

 Aeromonas, Vibrio and Flavohacter. Shewan described his 

 scheme, evolved over a number of years, for rapid diiferentiation 

 of these groups. 



Anthony ( Chapter 48 ) has conducted counts on the bacteria 

 of marine sediments with the object of determining the precision 

 of replicate estimates, and whether sediments of different regions 

 could be distinguished from one another on the basis of mem- 

 brane filter counts. The expression of accuracy was one wliich had 

 been developed for lake counts, namely the condition under 

 which four trips are made, and upon each trip, four sediment 

 cores are taken, and from each of the cores, four filters are pre- 

 pared for counting. With lakes, the standard error of the mean 

 had been about ±35 per cent, but in the marine habitat, it was re- 

 duced to something like % of that value. An encouraging feature 

 was that sediment samples could be frozen and held at — 20 C for 

 over 6 months without change in the counts; this may be of some 

 advantage for sea cruises, where rough weather makes certain 

 techniques difficult. Direct counts, made with the acridine orange 

 fluorescence technique of Strugger, were not in satisfactory agree- 

 ment with the membrane filter results. On the basis of filter 

 counts, three regions proved to differ significantly in the bacterial 

 counts of their sediments. Maximal was a strait where the water 

 is warmed through to the bottom in summer, and drains a good 

 farming area. Coastal waters draining inhospitable granite-slate 

 areas were appreciabb' lower. Finally, the continental shelf waters 

 were only about 1/10 those of the strait. It should be noted that 

 all counts were so low as as to constitute near sterilitv. 



Sieburth ( Chapter 49 ) reported on Antarctic microbiology, a 

 topic on which there are relatively few studies. He suggested that 



