Qua?ititativc Significance of Microorganisms in Nutrition 703 



(Fig. IC), the rate of this diminishing noticeably slackening as 

 food enters into the hind-gut. The same regularity was established 

 in another representative of the family Cardidae, Adacna plicata. 

 ZoBell and Feltham (31) extracted from the intestinal tissue of 

 the molluscs a fennent which provokes lysis of 28 strains of sea 

 water bacteria. Yong (29) mentions that small particles of food, 

 including bacteria, can be digested intercellularly by means of 

 phagocytes, which exist in the fore- as well as in the mid-part of 

 the intestine of molluscs. Digestive ferments are secreted on the 

 border of the oesophagus and the stomach, where the uptake of 

 digested food takes place by the special organs-diverticules. 

 Hence, microorganisms are digested in the intestine of molluscs as 

 well as in the intestine of Articidata identically, that is, when the 

 food passed the fore-part of the intestine and entered its mid- 

 part. No further multiplication of survived bacteria takes place 

 because of the acid reaction of the medium, whicli reaches pH 

 3 in the intestine of molluscs (29, 30). 



The fact that bacterial cells are digested cannot be regarded 

 as proof that they are assimilated. Digestive ferments could have 

 effected the lysis of bacterial cells. The ability of the newly 

 hatched young of Nereis diversicolor for assimilation of bacterial 

 cells was tested experimentally. Worms were offered food of 

 different composition (table 2). It was found tliat the young of 



TABLE 2 



Results of Growing Young Nereis diversicolor Fed 

 ON Various Food-materials 



Food Initial Total Increase 24 Hours Food 



Materials Weight of in Weight in Increase in Coefficient 



Worm in mg Course of the Weight 

 Experiment 



In %% from the initial weight 



Vegetable 49^0 22^5 13 27^3 



Yeast 45.7 91.2 6.0 4.9 



Bacteria 74.8 12.3 0.9 15.5 

 Control (animals 



were not fed) 60.0 -18.4 -1.3 — 

 Natural sediment 



(Jablonskaya and 



Belyaev) — — 4-7 142.1 



