498 Marine Microbiology 



variety of the microbial forms lixiiig in the depths of seas and 

 oceans. 



The microbiologist has now at his disposal: the "bathy- 

 sphere" which allows him to look into the deepest localities of 

 the oceans; the method of ultrafiltration, on membrane filters of 

 considerable amounts of water, compared with the size of a bac- 

 terial cell (in the ultrafiltration of 15-20 mis the microbial pop- 

 ulation is studied in a volume of water some 10^^ times greater 

 than the mean volume of a bacterial cell ) ; as well as the applica- 

 tion of the submerged slides method. These allow one, as it were, 

 to descend with a microscope to the required depth and to be- 

 come acquainted with its microbial population. Such "descents" 

 first carried out in tlie Black Sea, Caspian Sea and Sea of Okhotsk, 

 in the Pacific and Arctic Oceans, revealed an entirely new world 

 of microscopical organisms which, so far, have been unknown. 

 Tentative studies with the use of the electron microscope sug- 

 gest that, together with the smallest microorganisms, there exist 

 ultramicroscopic noncellular forms of life in the seas and oceans. 



Naturally, the study of the biology of the common fonns of 

 microorganisms in seas and oceans is one of the direct tasks of 

 marine microbiology. Tlie difficulties here are great when we 

 take into account tlie poor progress made in the development of 

 methods for culturing microorganisms living in nature. The de- 

 velopment of the ecological and physiological aspects of a study 

 of microbial species in their natural environment would over- 

 come these difficulties. 



It is necessary to intensify, in every possible way, marine 

 microl:)io]ogical investigations in order to satisfy the demands 

 placed upon them by the field of oceanography and general mi- 

 crol3iology. 



Without a wide participation of microl:)iologists it is im- 

 possible to study the basic oceanographical problems, and con- 

 sequently to realize the regularities underlying the productivity 

 of tlie waters of seas and oceans in the interests of practical 

 human activities. 



