704 



Marine Microbiology 



Nereis diversicolor, being fed for fourteen days exclusively on 

 bacteria, did not perish; moreover, they increased in weight by 

 12.3 per cent of the original weight. 



Having made certain that microorganisms had been assimi- 

 lated in the intestine of analysed animals, we attempted to calcu- 

 late the twenty-four hours' consumption of bacteria from quanti- 

 tative data on tlie diminution of the number of bacterial cells 

 when the food mass passes from the fore-part of the intestine to 

 the mid-part. We calculated mass of digested cells from the data 

 of the cells' volume. Specific weight of microorganisms was taken 

 as equal to 1 ( Table 3 ) . It has been found that under conditions 

 of the northern part of the Caspian Sea and in the places where 

 the samples had been taken, the microorganisms supply from 1 

 to 10 per cent of the twenty-four hours' nitrogen requirement 

 of the sediment invertebrates. 



TABLE 3 



The Twenty-four Hours' Food Ration of 

 Invertebrates (in Damp Weight) 



* According to Karpevitch and Jablonskaya (9). 



It is more difficult to determine the quantitative role of mi- 

 crobial cells in the nutrition of planktonic forms. Although Daph- 

 nia magna was used in most of works where qualitative methods 

 were made use of, its small size greatly complicated the task of 

 obtaining quantitative data for this plankter. The method of 



