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The length, weight, calorific value and organic matter content of Calanus finmarchicus, Stage V, males and females, were measured in monthly samples taken from April 1962 to June 1963.There is considerable variation throughout the year and all stages had their maxima of weight and calorific value in spring, 1962, and winter 1962–63.The calorific value and weight are closely correlated so that, knowing the dry weight, the calorific value can be calculated from it. The correlation is closest in Stage V and, for these, only the dry weight need be known. Since the relation-ship is slightly different for males and females the sex of the adult must be known as well as the dry weight; curves showing these relationships are given.The calorific value obtained from organic-matter analysis at times deviates widely from the values obtained in direct bomb calorimetry, and it is concluded that in the method used not all the fat is accounted for.In weight, calorific value, and organic matter, but not in length, Stage V for a good part of the year show higher figures than adults.In comparing the weights with those of other years and other places, the annual pattern is found to vary considerably. The spring maximum seems to occur every year, but there may be either a maximum or a minimum in autumn and winter.

The heat content of copepods and other microcrustaceans and two species of algae in calories per gram varied from 4427 for immature crayfish to 5643 for the female Diaptomus siciloides. The algae, cladoceran, anostracan, conchostracan, and immature crayfish were all below 5000, whereas all the copepods were above 5300 (x 5467); thus copepods may contribute more energy to the food chain on a weight basis than other lower forms of crustacea.

Tho development of a Diaptomus ashlandi population and the simultaneous phytoplankton cycles in Lake Washington, Seattle, were studied in samples taken from October 1949 to October 1950. The lake is 8762 ha in area and 65.2 m deep in its dccpcst part.Tcmpernturc measurements showed that stratification began late in March, and the surface maximum of 22.2" C occurred late in August.Typically the epilimnion was 10 m deep, the thermocline 10 m, and hypolimnion 40 m. Chemical determinations showed the lake to be slightly alkaline usually, but during the summer months the pH was above 8.0. Alkalinity ranged from 0.246 to 0.524 millcquivalents/litcr.Phosphate determinations showed a winter maximum and summer minimum in the surface and 15 m water, with an accumulation in the bottom waters as summer progressed.Dissolved oxygen was abundant, but in the hypolimnion was depleted at the rate of 2.0 mg/cmz/month during the summer.

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