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 tomake 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 forthe various localities the yearly 
averages of plankton, silt, and total catch, and the number of 
collections in each year. 
