NORTHWESTERN LAKES OF THE UNITED STATES. 
101 
LAKE PADDEN, WASH. 
Lake Padden is one of the small, shallow lakes with the maximum amount of 
net plankton per cubic meter of water concentrated in the surface stratum. Biap- 
tomus oregonensis and Diaphanosoma brachyurum predominated, and nearly 90 per 
cent of each species was found in the 0-3 m. stratum. All of the Daphnia longispina 
var. hyalina, Bosmina longispina, and Chydorus sphsericus were confined to the 0-3 
m. stratum. 
The maximum number of nauplii per cubic meter of water was also in the sur- 
face stratum. Over 92 per cent was found in this stratum. (See Table 12, p. 129.) 
The rotifers, too, were most abundant near the surface. All of the Conochilus, 
85.7 per cent of the Polyarthra platyptera, and 69.5 per cent of the Mastigocerca were 
in this region. Notholca longispina was found in the 3-6 m. stratum. 
Fairly large numbers of Ceratium and Anabsena were found at all depths, with 
the maximum number per cubic meter of water in the 0-3 m. stratum. Likewise, 
Anabsena was found at all depths in fairly large numbers, with the maximum num- 
ber per cubic meter of water in the 0-3 m. stratum. Ccelosphserium was obtained 
in the 3-6 m. stratum. Asterionella was the only diatom found in the lake. It 
occurred most abundantly between 3 and 6 m. 
PARADISE LAKE, WASH. 
The maximum number of Crustacea per cubic meter of water in Paradise 
Lake, which is only 8 m. deep, was in the 0-2 m. stratum. About 90.9 per cent of 
the Epischura nevadensis, 67.5 per cent of the Cyclops bicuspidatus, and 73.7 per 
cent of the Daphnia longispina were found in this stratum. (See Table 12, p. 129.) 
The absence of free oxygen at the bottom of the lake accounts for the scarcity of 
Crustacea in the 6-8 m. stratum, only a few Cyclops being found there. 
The largest number of nauplii, or 73 per cent of the total number, was in the 
0-2 m. stratum of the lake. None was found between 6 and 8 m., where there was 
a very small amount of dissolved oxygen. 
The rotifers were most abundant, also, between the surface and 2 m., with 
none at the bottom of the lake. Polyarthra platyptera comprised 36.8 per cent, 
Anursea aculeata and brevispina 24.6 per cent, Notholca longispina 36 per cent, and 
Conochilus and Asplanchna 2.5 per cent of the total number of rotifers. 
The maximum number of algae per cubic meter of water was found in the 0-2 
m. stratum. 
LAKE SAMISH, WASH. 
The thermocline of Lake Samish was between 8 and 12 m., and over three- 
fourths of the Crustacea were above this region. This was due to the fact that 
nearly all of the Biaphanosoma leuchtenbergianum and 70.3 per cent of the Cyclops 
bicuspidatus were above 8 m. 
Over half of the nauplii were below the thermocline, with 28.1 per cent 
between 16 and 20 m. Many nauplii were found at the bottom of the lake, where 
only a small amount of free oxygen was present. 
The maximum number of rotifers per cubic meter of water was in the 0-4 m. 
stratum. Mastigocerca comprised 87 per cent of the total number of rotifers and 
