504 
the question whether there is in this fluviatile environment a 
normal regimen of production. Is there in the course of pro- 
duction an orderly sequence, of any sort, of sufficient stability 
and of sufficient frequency in occurrence in successive years to 
justifiy its designation as a normal regimen? 
A cursory inspection of the planktographs in the plates, of 
the data in the plankton tables, and of the table of monthly 
means following page 342 reveals at once an apparent state of - 
chaos that accords well with the instability of most of the en- 
vironmental factors of the plankton, notably the hydrographic. 
For example, the production in the same month in different 
years or in the different localities examined by us is exceeding- 
ly variable. Taking at random the month of August, we find 
that the mean production for this month in the years of exam- 
ination ranges in the channel from .91 to 9.67; in Spoon River 
from .002 to .652; in Quiver Lake from .22 to 2.46; in Dogfish 
Lake from 1.11 to 3.91; in Flag Lake from .03 to 3.74; in 
Thompson’s Lake from 1.08 to 19.40; and in Phelps Lake from 
8.80 to 139.85 cm.’ per m.*; and, furthermore, that the extreme 
range in these means—.002 to 139.85— is found coincidentally 
in the same year, 1898 (see table following p. 342). This does 
not afford a very satisfactory basis for predicting the probable 
August production in cubic centimeters of plankton in any of 
these localities. It is evident that there is little regularity in 
the actual amplitude of production in a given season and locality 
in successive years. 
If the problem be approached from the standpoint of rela- 
tive production in different localities at the same time, or in 
the same locality at different times, more semblance of order 
is traceable, though not equally so in all localities or in all 
months of the year. The relative rank of each locality in mean 
monthly production, as seen in the table following page 342, 
is tabulated below. For example, in the case of the Illinois 
River in the total of 51 monthly means there were 5, 6, 16, 12, 
4,10, and 1, instances when its production attained first to sev- 
enth rank respectively among the seven or less localities repre- 
