THE METABOLISM OF EGGS, I 59 



Cleland (ig^oa) was unable to observe any decline in O^ uptake 

 with time after removal from the ovary, in unfertilized oyster eggs, 

 in Warburg manometers. But sooner or later, being shaken in 

 manometers has an injurious effect on unfertilized eggs, which is 

 reflected in pathological increases in O2 uptake. Alternatively, the 

 apparent increases in the O2 uptake of unfertilized eggs may be 



Si 



o» 

 o 



I 



POST-FERTILIZATION RATE 



PRE -FERTILIZATION RATE 



400 



Minutes after removal from ovary 



500 



FIG. II. — Comparison of pre- and post-fertilization O2 uptake of eggs of Psani- 

 mechinus miliaris, after Borei (1949). The asymptotic O., uptake of the un- 

 fertilized eggs, 5-10 ~ * /Ltl02/hour/egg, is only about yth of the O^ uptake in 

 Fig. 13- 



due to the growth of bacteria in the suspension, though, admittedly, 

 it takes some while for this effect to become significant. Tyler et 

 al. (1938) carried out some interesting experiments, Fig. 12, com- 

 paring the respiration of unfertilized eggs of Arbacia punctulata in 

 sterile and non-sterile media. The experiments show that con- 

 tamination of cultures with bacteria and the metabolism of the 

 latter are factors which require careful attention in experiments of 

 this sort. Some of these factors may explain Cleland's results; but 



