428 



are considerably larger in Phelps Lake than in the other lo- 

 calities. 



The course of production in this lake, as has been shown, 

 is predominantly like that in the other localities. It frequent- 

 ly has similarly located pulses, though their amplitude, es- 

 pecially in late summer and autumn, is often much great- 

 er than elsewhere. Moreover, in the majority of instances the 

 direction of the changes in production in coincident or approx- 

 imate collections is also similar to that elsewhere. In a total 

 of 260 possible instances there is agreement in 169, or 65 per 

 cent. This excess of agreement over the demands of chance, 

 combined with its recurrence in successive years and its occur- 

 rence in the case of different localities, is confirmatory of the 

 view that it is the result of the operation of common factors 

 of the environment. The predominance of the disagreements 

 at times of greatest local differentiation or disturbance, as in 

 low water in summer or in rising floods, lends further support 

 to the suggestion. 



GENERAL COMPARISONS OF YEARS AND STATIONS. 



It is my purpose to summarize in the following pages the 

 results set forth in detail with respect to the individual locali- 

 ties in the several years, and to make the comparisons and draw 

 the conclusions which follow from such a summary regarding 

 the relative production in these different years and localities 

 and the factors operative in modifying production. 



The following table gives for the various localities the yearly 

 averages of plankton, silt, and total catch, and the number of 

 collections in each year. 



