505 
RANK IN PLANKTON PRODUCTION. 
eas . Thomp- ‘ 
Illinois | Spoon | Quiver | Dogfish Flag 2P-| Phelps 
Rank River River Lake Lake Lake Lal = Lake 
ake 
De cceesiivsess 5 fe) 4 2 4 13 28 
3 Se POAT 6 I 2 2 II 27 4 
LS ree Sere 16 I 14 10 I 38 I 
Premises eee 12 I 14 8 5 3 I 
Gia weneurics ees 4 12 15 2 z ° I 
Gitar nnislacoa ers 10 5 4 fe) fo} ° I 
“ASA OT oe I 8 fe) fo) fe) fe) fo) 
Otal ye. Joa <s 51 28 53 24 23 51 36 
Average rank 3.9 5.6 -4 353 2.6 2. ELS 
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 table. 
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 relations of production 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 
