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 1.1 1 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. 3 per m. 3 ; 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- 



