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 (zodplankton) 
portions of the plankton can be separately expressed in terms 
of acommon 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 
