417 
the main representative of the plankton of the lake. Of the 67 
collections, 32 were taken from water which in the deepest part 
of the neighborhood of collections was less than 14 inches. 
Owing to the roiling of the water caused by our movements, it 
was necessary to dip from considerable areas in order to secure 
the desired volume for straining. 
Since a separate report on these collections is being pre- 
pared I shall only deal in this connection with those aspects of 
the data most intimately connected with the phenomena of 
the channel plankton. 
PLANKTON PRODUCTION, 
1894. 
(Table IX.) 
A single collection on June 8 yields a volume of 24.17 em. 
per m.*, an amount 7-fold that of the same season in 1896, al- 
most equaled in 1897, and more than doubled in 1898. 
1896. 
(Table IX., Pl. XL.) 
There are 29 collections in this year, extending from Jan. 
8 to Noy. 17—when only a few scattered pools remained. This 
is the most fully represented year of our series in this lake. 
The yearly average is 13.17 em." per m.*, with a vernal maxi- 
mum of 54.80 on Apr. 16, and an autumnal one of 51.60 on Oct. 
15. This is the earliest vernal pulse recorded in our work, and 
should be correlated with the early rise in temperature in these 
shoal and protected waters. Thus, in Phelps Lake on Apr. 16 
the surface temperature was 77° and the average for April 68.4° 
to-7L° (Apr. 17) and 62.6° (average) in Quiver Lake, and to 66.5° 
(Apr. 17) and 63.2° in the Lllinois River. This: lake was thus 
apparently 5° to 6° warmer on the average than these other 
localities, and the vernal pulse is accordingly accelerated. 
Owing to the elevations of the lake and its outlet, run-off 
from this area into channel waters practically ceases when 
river levels fall below 8 ft. In 1896 there were but 114 days of 
