Abstract
Though all workers have agreed that the respiration of Arbacia eggs increases about 5 times on fertilization, there is disagreement as to the absolute values. Since some theoretical importance attaches to these magnitudes, it seemed desirable to resolve the discrepancies. The most recent determinations by Tang 1 and Tang and Gerard 2 and by Whitaker 3 all utilized the Warburg manometrie technique, yet apparently differed by a factor of nearly 2. Expressed as cubic millimeters of oxygen used per 10 cu. mm. of eggs per hour (at 21 °C), the former observers obtained for resting eggs, 0.8; the latter, 0.4-0.5. Differences in technique included: securing the eggs and preparing the suspension; shaking in the manometers; determination of egg volume; and experimental temperature. All these points have been checked by direct comparison of the 2 techniques at each step. The figure obtained in the present series is 0.9.
The results show that whether eggs are obtained by picking out ovaries or allowing the eggs to shed from the gonopores of the half shell is immaterial. Likewise, mild hand centrifuging or filtering through cheese cloth has no effect. Further, both the shaking rates used permitted an adequate oxygen supply without injury to the eggs.
A major difference appeared, however, in the techniques for evaluating egg volume. The egg volume determined by centrifuging a given amount of suspension to constant egg mass was regularly about 80% greater than that calculated from the egg diameter (determined with ocular micrometer) and cell count (with haemocyt-ometer). That the centrifuge method is in error, due to imperfect packing, egg jelly, etc., was further shown by examining an egg mass in the Harvey centrifuge-microscope. During strong centrifuging individual eggs remained widely separated, often by a full egg diameter. Applying this correction to Whitaker's figures, they are in essential agreement with ours and Tang's. Of especial interest was the influence of temperature on egg respiration. The temperature coefficient for fertilized eggs was slightly under 2, between 11° and 30°C, essentially as reported by Loeb and Wasteneys. 4
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