98 
BULLETIN OF THE BUREAU OF FISHERIES. 
The maximum number of nauplii per cubic meter of water was found just 
below the thermocline, or in the 6-9 m. stratum, and just above the region having 
a very small amount of oxygen. 
The largest number of rotifers per cubic meter of water occurred in the 0-3 m. 
stratum. The lower stratum of the lake between 9 and 12 m. was entirely devoid 
of them. Polyarthra platyptera comprised 83.2 per cent of the rotifers, and over 
three-fourths of this number were in the 0-3 m. stratum. A few Anuraea coch- 
learis were found between 6 and 9 m. Noiholca longispina was found above 9 m., 
with the maximum number per cubic meter of water between 3 and 6 m. 
Mallomonas was found between 3 and 9 m. 
Anabsena was obtained in the 0-3 m. stratum and Microcystis in the 3-9 m. 
stratum. The diatoms showed an irregular vertical distribution. 
COTTAGE LAKE, WASH. 
The maximum number of Crustacea per cubic meter of water in Cottage Lake 
was found between 2 and 5 m. Eighty-six per cent of the Cyclops bicuspidatus 
and a very small number of Diaphanosoma leuchtenbergianum were in this stratum. 
All of the Epischura nevadensis, which composed one-fourth of the Crustacea, were 
in the 0-2 m. stratum. 
Almost three-fourths of the nauplii were in the 0-2 m. stratum. A few were 
found below the thermocline. 
Among the rotifers, all of the Polyarthra platyptera and Anuraea aculeata were 
in the surface stratum. About 73 per cent of the Notholca longispina and all of 
the Mastigocerca were in the 2-5 m. stratum, which contained the maximum num- 
ber of rotifers per cubic meter of water. (See Table 12, p. 125.) 
Epistylis, Dinobryon, and Ceratium were found in the upper 2 m. 
Aphanocapsa was noted only between 0 and 2 m., and Anabsena was obtained 
at all depths. The diatom Cyclotella was noted in the 0-2 m. catch and Asterio- 
nella in the 2-7 m. stratum. 
COW LAKE, WASH. 
Over three-fourths of the Crustacea in Cow Lake were above the thermocline, 
or above 8 m., with the maximum number per cubic meter of water in the 0-4 m. 
stratum. All of the Bosmina longirostris and Epischura nevadensis, which together 
composed about two-thirds of the Crustacea, and 85 per cent of the Daphnia longi- 
spina var. hyalina were in the 0-8 m. stratum. There were no Crustacea between 
16 and 20 m., but a few Cyclops modestus occurred in the 20-24 m. stratum. 
The nauplii, also, were confined largely to the region above the thermocline, 
with the maximum number per cubic meter of water in the upper 4 m. Eighty 
per cent of the nauplii were above 12 m., with 27.8 per cent in the 0-4 m. stratum. 
The maximum number of Rotifera per cubic meter of water was found in 
the epilimnion, especially in the 0-4 m. stratum of the lake. 
Specimens of Ceratium and Dinobryon were secured between 4 and 12 m. 
They were not found above or below this stratum. 
Asterionella was the only diatom found in Cow Lake and was confined entirely 
to the 0-4 m. stratum. 
