NUTRITION AND METHODS OF FEEDING 187 



is no longer valid. As already hinted, however, Putter's 

 views are not generally accepted by authorities in this country. 

 The opinion of Benjamin Moore and others (19 12) is that 

 neither the dissolved organic matter nor the average amount 

 of suspended plankton is sufficient to account for the 

 nutrition of the larger of the marine forms. The large 

 animals either distribute themselves along pathways, 

 and in situations, where the supply of food is above the 

 average, or follow up actively richer growths of minute 

 organisms. Or, again, they may capture animals of greater 

 size than those of the minute plankton, which animals, in 

 turn, feed upon microscopic plankton, or upon vegetation 

 occurring along the sea-shore or upon the sea-bottom. 



Bacteria in the Sea. — ^When plants and animals die the 

 substances which compose their bodies do not pass out of 

 circulation, but by a series of changes (putrefaction, fermenta- 

 tion, etc.) are split up into their ultimate constituents and 

 again made available for life. This work is effected by the 

 agency of certain micro-organisms : bacteria, yeasts, and 

 moulds, the importance of which in the economy of nature 

 is fundamental. We are on familiar enough ground here, 

 but it is important to remember that, until quite recently, 

 our knowledge of these organisms in the sea was very scanty. 

 Thus, even in 1908, all that could be said of fermentative 

 bacteria in the sea was that they " doubtless exist . . . though 

 we have little knowledge of their distribution " (Johnstone, 

 op. cit.). Fischer, in 1894, was the first to carry out a really 

 extensive investigation of marine bacteria. Keutner and 

 Keding first signalled the occurrence of nitrogen-fixing 

 bacteria {Clostridium and Azotohacter) in the sea in 1895-6 

 and the discovery of marine denitrifying bacteria was made 

 almost simultaneously by both Baur and Gran in 1898. 

 Thanks to these and similar researches, it is now definitely 

 known that there occur in the sea putrefactive and fermen- 

 tative organisms of the same nature as those previously known 

 elsewhere. In addition, there are also present in the sea : 

 nitrogen-fixing bacteria capable of utilising atmospheric 

 nitrogen for the formation of proteids ; denitrifying bacteria 



