226 



A third reason for the absence of proportional correlation 

 between the movements of the organic nitrogen and the fluc- 

 tuations of the plankton lies in the cumulative nature of the 

 latter as contrasted with the non-cumulative character of 

 changes in the chemical substances at whose expense it 

 increases. Growth and reproduction of organisms is funda- 

 mental in the plankton pulses, and there is nothing comparable 

 to either of these in the chemical changes of non-living 

 matter. 



It remains only to discuss the correlations that do appear 

 between the albuminoid ammonia and total organic nitrogen, 

 on the one hand, and the plankton, on the other. The two 

 diverse tendencies noted in the preceding pages, the one for 

 the plankton pulses of warm months to coincide with a 

 decrease in these nitrogenous matters, and the other for the 

 pulses of cold months to coincide with an increase in these 

 substances, or at least in the organic nitrogen, will be fully 

 accounted for only when the changes in the different elements 

 included under these common designations, the dissolved por- 

 tion, the silt, and the plankton, shall be differentiated, and when 

 the changes in the different kinds of organic nitrogen shall be 

 separately unraveled, and, furthermore, when the fluctuations 

 of the synthetic (phytoplankton) and analytic (zooplankton) 

 portions of the plankton can be separately expressed in terms 

 of a common unit. It is evident that the available chemical 

 analyses and volumetric and statistical determinations of the 

 plankton do not afford such comprehensive data. The incom- 

 plete data at hand throw some light, however, upon the nature 

 of the correlation, and suggest the probable explanation for 

 the two divergent tendencies noted and the numerous excep- 

 tions thereto. 



As has been previously shown, plankton pulses are usually 

 coincident, or nearly so, with an upward or a downward move- 

 ment in the nitrogenous substances, organic and inorganic. 

 The upward movements of the albuminoid ammonia and 

 organic nitrogen and the downward movement in the nitrates 



