NORTHWESTERN LAKES OF THE UNITED STATES. 
103 
LAKE SPANAWAY, WASH. 
This lake is very much the same as Lake Steilacoom, but it has a very much 
smaller amount of plankton. The largest number of Crustacea per cubic meter 
of water was in the 0-2 m. stratum. Almost two-thirds of the Crustacea were 
Epischura nevadensis, and 65 per cent of this number were in the surface stratum. 
Diaphanosoma leuchtenbergianum was confined to the upper 4 m., and Bosmina 
longirostris to the upper 2 m. 
The nauplii, likewise, were most abundant in the surface stratum. About 80 
per cent of them had congregated in this region. (See Table 12, p. 131.) 
Only two species of rotifers were found in this lake, and the maximum number 
was in the 2-4 m. stratum. Notholca longispina comprised almost three-fourths of 
the total number of rotifers, and about 60 per cent were in the 2-4 m. stratum. 
In addition to the Notholca, a few Anursea cochlearis were found between 4 and 
7 m. The maximum number of algse per cubic meter of water was noted in the 
0-2 m. stratum. 
LAKE STEILACOOM, WASH. 
This lake is very shallow. The maximum number of Crustacea per cubic 
meter of water was obtained in the 0-2 m. stratum. The Crustacea consisted of 
57.9 per cent Epischura nevadensis , 17.3 per cent Ceriodaphnia reticulata, 20 per 
cent Bosmina longirostris, and a few Diaphanosoma leuchtenbergianum and Daphnia 
longispina var. hyalina form galeata. 
Seven-eighths of the nauplii were in the 0-2 m. stratum also, and three-fourths 
of Notholca longispina were in this same region. 
No diatoms were found in the limnetic catches. Mougeotia and Anabsena 
were the only algae found. A very large number of Anabaena was found in the 
surface stratum, and Mougeotia was found between 2 and 5 m. 
LAKE STEVENS, WASH. 
The Crustacea in Lake Stevens had a rather uniform distribution with the 
maximum number per cubic meter of water in the 0-5 m. stratum. This was 
due to the large number of Epischura nevadensis in this region and to the fact that 
all of the Diaphanosoma leuchtenbergianum were confined to this stratum, too. 
Cyclops bicuspidatus was well distributed throughout the lake, with the maximum 
number per cubic meter of water between 5 and 10 m., or in the region of the 
thermocline. 
Nauplii were found mainly in two separate regions of the lake, namely, above 
10 m. and between 35 and 45 m., with the maximum number per cubic meter of 
water in the bottom stratum. About one-half of the nauplii were above 10 m., 
and 43.9 per cent in the 35-45 m. stratum. 
Notholca longispina and Anursea brevispina comprised over two-thirds of the 
rotifers. Notholca was most abundant in the surface stratum, Anursea in the 
bottom stratum. All of the Triarthra and Polyarthra platyptera were found in the 
upper water. Mastigocerca was distributed throughout the entire lake, with the 
maximum number per cubic meter of water in the 0-5 m. stratum. 
The maximum number of algse per cubic meter of water was found in the upper 
10 m., but a relatively large number was found at all depths. 
