219 
plankton pulses of 1897 (Pl. XLVI.) in the warm months of 
May.and September, but the increases noted with the pulses of 
plankton in the winter in the Illinois River are not apparent 
in the case of the pulses of February and December in this 
stream, though no decrease appears as in the summer months. 
In Quiver Lake in 1898-99 (Pl. XLVIII.) a seasonal move- 
ment in the albuminoid ammonia and the organic nitrogen is 
evident, though it seems to accompany the access of sewage- 
contaminated waters of overflow, as appears on comparison 
with the chlorine curve. This seasonal movement is evident 
as a depression of the curves during the warm and low-water 
months, and as an elevation during the colder months of the 
flood period. As in Illinois and Spoon rivers, the plankton 
pulses in Quiver Lake of the warm period, in May and June, are 
attended by a temporary decrease in these nitrogenous sub- 
stances. A still more marked decrease in both albuminoid 
ammonia and organic nitrogen attends the winter pulse of 
plankton in February, 1899, while that of the preceding De- 
cember appears with an upward movement of the organic 
nitrogen and a downward one in the albuminoid ammonia. 
The correlation between the movement of albuminoid am- 
monia and organic nitrogen and of the plankton is thus in this 
instance (predominantly, at least) similar to that noted else- 
where in the warmer months. The very slight ripples in the 
plankton curve in July, August,and September attend minor 
increases in these nitrogenous substances, a feature noted else- 
where in colder months. 
In Thompson’s Lake (PI. L.) the albuminoid ammonia, the 
organic nitrogen, andthe plankton are all more abundant and ex- 
hibit greater fluctuations than they do in Quiver Lake. These 
conform in a general way to the tendencies noted in other 
localities. The amounts present during the colder months, 
October to May, are a trifle greater than in the intervening 
warmer period. There is also a temporary decrease in those 
nitrogenous matters attending plankton pulses in the warm 
months. This appears with the pulses of June, July, and 
