NORTHWESTERN LAKES OF THE UNITED STATES. 89 
LOWER TWIN LAKE, IDAHO. 
Lower Twin Lake is a little deeper than Upper Twin and shows a true thermo- 
cline. The water in the upper stratum was slightly alkaline and supported a very 
large growth of algae. Other plankton forms appeared in small numbers, the 
Cladocera being the most numerous. (See Table 12, p. 128.) 
MEDICAL LAKE, WASH. 
The fact that Medical Lake was distinctly alkaline did not seem to affect 
the quantity or the vertical distribution of the plankton in any noticeable degree. 
It was well supplied with zooplankton. The amount of dissolved oxygen was 
somewhat smaller than in most of the lakes considered thus far, and it decreased 
toward the bottom of the lake. The thermocline was between 7 and 9 m. 
With the exception of Daphnia pulex and CeriodapJmia pulchella, the Crustacea 
were distributed throughout the depth of the lake, with the maximum number per 
cubic meter of water in the 0-4 m. stratum. (See Table 12, p. 128.) In the 0-4 m. 
stratum there were 38,000 Crustacea per cubic meter of water and in the 4-8 m. 
stratum 25,000; but in the 8-12 m. stratum there were only about 1,500. 
The nauplii had about the same distribution as the Rotifer a, with 11,590 per 
cubic meter of water in the 4-8 m. stratum and 3,640 above and 3,310 below this 
region. 
Rotifera were especially abundant at all depths. At the thermocline in the 
catch made between 4 and 8 m. there were 29,640 per cubic meter of water. Above 
this region there were only 4,640 and below it 1,490 per cubic meter of water. 
The algse seemed to be well distributed throughout the lake, but the numbers 
were small. In the 0-4 m. stratum there were 1,030 algae per cubic meter of 
water, in the 4-8 m. stratum 920, and in the 8-12 m. stratum only 130. The chief 
characteristic of this lake is the large quantity of zooplankton and the relatively 
small amount of algae. 
The large quantity of Crustacea and other animal life in Medical Lake ought 
to furnish an abundant supply of fish food, but because of the alkalinity of the 
water no fish will live there for any period of time. 
NEWMAN LAKE, WASH. 
Newman Lake is a small, shallow body of water, with 9 m. (29.5 feet) as the 
maximum depth. It shows no plankton distribution of unusual interest. The 
Protozoa were most abundant at the surface, and the nauplii were found in largest 
numbers at the bottom. There was no thermocline, and the water was alkaline 
from top to bottom. (See fig. 13.) 
PAYETTE LAKE, IDAHO. 
Big Payette Lake, Payette Lake, or Payette Lakes all apply to the same body 
of water, which is divided by a narrow neck into two basins. The southern basin, 
which is oval, is a little larger than the more irregular northern basin. It lies in 
northern Boise County, Idaho, and is reached by a 29 km. (18-mile) stage ride 
from New Meadows, Idaho. Its greatest length is 7.5 km. (4.6 miles). It is 4 
km. (2.5 miles) wide, and its elevation is 1;520 m. (4,987 feet). 
