. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 108 HANS BOREI AND SIGVAR LYBING EXPERIMENTAL DATA The experiments have been performed with Cartesian diver micro-respiration technique, suitable for measurement of the oxygen consumption of '—• 100 eggs at a time. Concerning material and methods, corresponding-chapters (; ; ) in Borei (1948a) should be consulted. Diver charge type I (Borei, 1948b) was used throughout. The temperature range was 10-21° C. The maximum temperature for normal larval development of Psammechinus inillaris has been studied by S. Ru
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 108 HANS BOREI AND SIGVAR LYBING EXPERIMENTAL DATA The experiments have been performed with Cartesian diver micro-respiration technique, suitable for measurement of the oxygen consumption of '—• 100 eggs at a time. Concerning material and methods, corresponding-chapters (; ; ) in Borei (1948a) should be consulted. Diver charge type I (Borei, 1948b) was used throughout. The temperature range was 10-21° C. The maximum temperature for normal larval development of Psammechinus inillaris has been studied by S. Runnstrom (1927), who found it to be 22° C.; the minimum temperature was found by this author to be 8° C. For measure- ments at lower temperatures, the cooling coil of the diver apparatus thermostat was fed with refrigerated salt-\vater of approximately +5° C. The desired temperature was obtained by counteracting the cooling device by operating a thermostatically controlled electric heating bulb. In order to obtain more comparable values, measurements were only performed on the flatter part of the declining respiration curve of the unfertilized egg (cf. Borei, 1948a, Chapter ). Thus the time of actual measurement usually ran from three to six hours after removal from the ovary. This means that the con- stant part of the respiration is dominant during the measurements, whereas the "rap- idly declining" part characterizes the preceding hours, during which the eggs were kept at 16-18° C. The eggs were, on an average, placed in the diver hours after removal from the ovary. The diver was then immediately placed in the thermo- stat at the experimental temperature and left there for a half hour for temperature equilibration before starting the measurements. Usually two diver thermostats were operated simultaneously, thus allowing measurements at two different tempera- tures. The time schedule of the experiments may be seen from Figure 1. LJ LJ 52
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