104 
BULLETIN OF THE BUREAU OF FISHERIES. 
SWAN LAKE, WASH. 
Although many Crustacea were found at all depths in Swan Lake, the maximum 
number per cubic meter of water was found in the 0-3 m. stratum. Over half of 
the Crustacea were above the thermocline. This was due chiefly to the large 
number of DiapJianosoma leuchtenbergianum, and Epischura nevadensis in this 
stratum. 
Although a few nauplii were found above the thermocline, by far the largest 
number was below this region, with the maximum number per cubic meter of water 
in the 9-12 m. stratum. 
Several species of rotifers were obtained in this lake. Conochilus was most 
abundant in the 0-3 m. stratum. The other species were rather uniformly dis- 
tributed throughout the depths of the lake. 
LAKE TAPPS, WASH. 
The vertical distribution of the Crustacea in Lake Tapps was peculiar in that 
the organisms were abundant at the bottom of the lake, between 20 and 24 m. 
There was a large number of Crustacea, also, in the surface stratum, with relatively 
few organisms between the surface and bottom strata. Daphnia longispina var. 
Jiyalina and Diaptomus eiseni composed about 84 per cent of the total number of 
Crustacea in about equal proportions. It is interesting to note in this connection, 
also, that 82.6 per cent of the Daphnia were in the 0-4 m. stratum and 84 per cent 
of the Diaptomus in the 20-24 m. stratum. 
The nauplii, also, were most abundant in the surface and bottom strata. 
The rotifers, likewise, had the same general distribution as the Crustacea and 
nauplii, with the maximum number per cubic meter of water in the surface and 
bottom strata and a decided decrease in number between these regions. 
Dinobryon and Ceratium were most abundant in the upper 8 m. 
Microcystis and Aphanizomenon were most numerous in the 0-4 m. stratum. 
The maximum number of diatoms per cubic meter of water was found in the 0-4 m. 
stratum. Below 4 m. only a limited number was found. Asterionella was by far 
the predominant diatom in the lake. 
LAKE WASHINGTON, WASH. 
Lake Washington lies partly within the city limits of Seattle. It is a long 
narrow body of water extending 32 km. on a north and south line with a width of 
7 km. The lake has been sounded and marked by the United States Geodetic 
Survey (Lake Survey, 1841-1881) which reports a depth of 37 fathoms. On account 
of the strong wind we were unable to locate this place, and our deepest sample was 
taken at 60 m. (32.9 fathoms). A canal was completed in 1916 that connects the 
lake and the sound and lowers the lake 3 m. 
The climate in this section is so mild that Lake Washington never freezes over, 
so it would be of interest to carry out determinations similar to these throughout 
the year. 
This lake showed a larger number of Crustacea per cubic meter of water than 
any other lake included in these studies. Although a certain amount of net plank- 
ton was found at all depths, over 65 per cent of the zooplankton was above 10 m., 
or above the thermocline. (See Table 12, p. 134.) 
