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BULLETIN OF THE BUREAU OF FISHERIES. 
stein’s Physical Chemistry Tables. Hamberg (1911) copies the above-mentioned 
table and concludes that we should have many examples of temperatures below 
4° C. in the deep fresh-water lakes. As he says, 10 m. of water adds, roughly, 
one atmosphere of pressure. When this is considered, together with the table that 
gives the temperature of maximum density at 10.5 atmospheres as 3.4° C., 41.6 
atmospheres 3.3° C., 93.3 atmospheres 2° C., one would expect even much lower 
temperatures than those found in Crater Lake. Hamberg then gives the tempera- 
tures of several Alpine lakes, the bottom water of which is below 4° C., but in no 
case is the temperature as low as those given in the above table for the same pressure. 
NET PLANKTON. 
The limnetic zooplankton consisted almost entirely of Daphnia pulex. Bosmina 
longispina was found between 100 and 150 m. The largest number of Daphnias per 
cubic meter of water was found in the 60-80 m. stratum of the lake in August and in 
the 50-60 m. stratum in September. In August no Daphnias were found above 40 
m., but in September a few were found between 30 and 40 m. There seemed to be 
more Daphnias in September than in August. (See fig. 19.) 
No nauplii were found. 
The Rotifera consisted largely of Asplanchna, with a few Notholca longispina 
and Anursea aculeata. The maximum number of Rotifera per cubic meter of water 
was found in the 60-80 m. stratum in August and in the 80-100 m. stratum in 
September. No Rotifera were found above 30 or below 200 m. 
A very small filamentous alga, probably Mougeotia, was found in fairly large 
numbers in Crater Lake. It was similar to the predominant alga found in Lake 
Tahoe, Calif. Its vertical distribution, also, was very much like that of Lake Tahoe 
alga, with the maximum number per cubic meter of water below 60 m. in both 
lakes. In Crater Lake the maximum number per cubic meter of water was between 
60 and 80 m. in August and 100 to 150 m. in September. 
Asterionella was the only diatom found in the lake. In August the maximum 
number per cubic meter of water was found between 150 and 200 m.; in Septem- 
ber, between 100 and 150 m. 
As a whole, the limnetic plankton was rather limited in supply. Around the 
shores of Wizard Island swarms of Daphnias were seen, and this may account to 
some extent for the fact that most of the trout were caught along the shores of the 
island. 
FALLEN LEAF LAKE, CALIF. 1 
Fallen Leaf Lake, a small beautiful mountain lake, is situated just south of 
Lake Tahoe, into which it empties through a stream that is now dammed for power. 
The lake is 6.5 km. long in a north and south direction by 2 km. east and west and 
has an elevation of 1,939 m. (6,360 feet), which places it 42 m. above Lake Tahoe. 
It lies just at the east slope of Mount Tallac, from which it receives a number of 
small mountain streams. It also receives a large amount of water from the moun- 
tains that lie to the south of it. 
1 We visited Fallen Leaf Lake during a rain that raised the level of the lake 15 cm. This may have reduced the clearness 
and changed the composition of the surface water. 
