702 



Marine Microbiology 



solely sucking. Hence, it is quite understandable, that the number 

 of microbial cells sharply diminishes as the food passes from the 

 fore-to the mid-gut. It is obvious that the number of digested 

 microorganisms represents the difference between the respective 

 numbers of cells in the fore- and mid-gut. The hind-gut contains 

 no ferments, and here the multiplication of undigested microbial 

 cells takes place. As proof thereof, the results of observations by 

 Winogradsky's technique, of the micro colonies consisting of a 

 few bacterial cells, showed that the number of bacterial cells in- 

 creases from the mid- to the hind-gut in Nereis diversicolor. 



Nereis 

 diversicolor 



Pontogammarus 

 maeaticus 



Monodacna 

 edentula 



PARTS OF INTESTINE 



Vig. 1. The change in number of microorganisms in 1 gm. of intestine 



content. 



The character of digestion of bacterial cells in the intestine 

 of Pontogammarus maeoticiis is analogous to that which was 

 found in Nereis, that is, the total number of cells diminishes in 

 passing from the fore- to the mid-gut and increases in the hind-gut 

 (Fig. IB). This phenomenon coordinates well with the facts of di- 

 gestion in Crustacaea. Digestive ferments in the representatives of 

 this group are secreted on the border of the fore- and mid-gut 

 (29). Uptake can take place only in the mid-gut, the fore- and 

 hind-gut being chitinized. 



In the molluscs (Monodacna edentula), imlike the represen- 

 tatives of Articulata, we observed the uninterrupted diminishing 

 of the number of microbial cells all along the digestive tract 



