505 



RANK IN PLANKTON PRODUCTION. 



sented in the months concerned. An examination of this table 

 shows that in relative production (see table following p. 342) 

 the localities tend to arrange themselves in a sequence which 

 is represented by the average rank. As shown in the above tables 

 this is as follows: Phelps Lake (1.5), Thompson's Lake (2.), 

 Flag Lake (2.6), Dogfish Lake (3.3), Illinois River (3.9), Quiver 

 Lake (4.), Spoon River (5.6). This is essentially the sequence 

 in relative production represented by the averages of all collec- 

 tions and of the monthly means (see table following p. 342), 

 except that Flag and Thompson's lakes are transposed. From 

 the points of view either of average rank or of average produc- 

 tion the rehifions of pyodudion in the 7 localities examined by 

 us are, it appears, essentially similar. A considerable measure 

 of stability in this respect may therefore be expected. 



If we inquire if these relations in production expressed in 

 terms of rank are equally constant for all localities and at all 

 seasons, we find that there are departures from the average in 

 all localities, and that different localities show different de- 

 grees of stability of relative production varying to some extent 

 with the season. This appears in a comparison of the ranks of 

 Phelps Lake and the Illinois River in the table above given. 

 In the case of Phelps Lake (average rank, 1.5) 32 of the 36 

 months rank first or second, while in the Illinois (average rank, 

 3.9) but 28 of the 51 rank third and fourth. Obviously the 

 divergences from the expected rank in production are greater 



