Comparison of Portable and Dark Room Autokinetic Movement

A portable apparatus for producing autokinetic (AK) movement is described and compared with the standard dark room method. Use of the portable apparatus results in a smaller amount and expanse of apparent movement, but the test-retest reliabilities are of the same order of magnitude as in the dark room method. The portable apparatus provides several advantages to the AK researcher. It is easy to handle; it can readily be disassembled; it eliminates the ventilation and light-proofing problems inherent in achieving a totally darkened room. This apparatus automatically measures the latency of onset of AK movement. The importance of controlling or measuring the latency of onset of AK movement is demonstrated.

Experimental Determination of Food Consumption of pike, Esox lucius, for Growth and Maintenance

Under laboratory conditions simulating those in the field, there were seasonal changes in both growth and in maintenance requirements of pike (Esox lucius), which were to some extent independent of temperature. The peak maintenance requirement of about 45 mg of minnow (Phoxinus phoxinus) per gram of pike occurred in late June, followed by a decline through August and September until a fairly steady state of about 25 mg/g was reached in October. Maintenance continued at this level until April when there was a gradual rise to the June peak. The maintenance coefficient was 1.385 g per gram per annum, and there was no apparent decrease with size. Growth also reached a peak in June then declined through the rest of the summer and fall until it ceased in midwinter. Growth resumed in March, the rate gradually increasing until the June peak was reached. After maintenance requirements have been met, 1 g food produces.437 g pike when feeding is ad libitum. The maximum value of the coefficient of utilization is.485, at a level of feeding below that of maximum intake. The efficiency of utilization at the maintenance level is.476. Comparing the results with those reported for other species shows that pike have relatively low maintenance requirements and relatively high values for the conversion of food to pike substance.

Consumption of Food by the Resident Population of Pike, Esox lucius, in Lake Windermere

The annual consumption of food, the annual production, and the yield of pike in Windermere are determined from equations devised by Beverton and Holt (1957). The determination of the various population parameters is described and these are combined with the results obtained from the experimental determination of food consumption to provide numerical solutions. Prior to the start of heavy exploitation in 1944 the biomass is estimated to have been 8182 kg with an annual consumption of 22,124 kg. After 10 years of fishing the biomass has been reduced to 4349 kg with a consumption of 16,563 kg; this represents a 47% reduction in biomass for a 25% reduction in consumption. These results are discussed in terms of cropping the annual production of the lake.

Temperature Regime of Deep Lakes

New data concerning the temperature of maximum density of fresh water under pressure have been obtained in Great Bear Lake, in the Northwest Territories of Canada. Previous theoretical determinations are discussed; Strom's empirically determined figures are in agreement with these data.

Arteritis in Rheumatoid Arthritis

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