EGG SECRETIONS OF ARBACIA AND ASTERIAS 



493 



On the other hand, if the eggs be allowed to settle in test-tubes 

 and only the supernatant fluid be tested, it will be found that the 

 liquid above the unfertilized eggs combmes less readily with io- 

 dine than does that above the fertilized eggs. The first inference 

 from this was that the fertilized eggs had excreted unsaturated 

 fattj^ acid into the sea-water. If, however, we add to the water 

 poured off from unfertilized eggs an amount of sperm suspension 

 equal to that present in the other tube, we find that iodine is ab- 

 sorbed in equal amounts from each. Therefore, the results were 

 due to the presence of sperm in the water above fertilized 

 eggs, rather than to unsaturated acid excreted at the time of 

 fertilization. 



TABLE 17 

 The effect of iodine on resistant or overripe Arbacia eggs 



1. 10 cc. eggs + sperm, control 



2. 10 cc. eggs + 1 drop saturated iodine 10 minutes + 

 sperm 



3. 10 cc. eggs -r 2 drops j saturated iodine 10 minutes + 

 sperm 



4. 10 cc. eggs + 1 drop j saturated iodine 10 minutes + 

 sperm 



5. 10 cc. eggs + 1 drop | saturated iodine 10 minutes -{- 

 sperm 



24 



28 

 36 

 50 



29 

 39 

 44 

 48 

 31 



81 

 40 

 62 

 61 



Neither Asterias nor Arbacia lipolysin seems to combine with 

 iodine. The chemical parthenogenetic agents, however, react 

 with the fatty inhibitor, and, as we saw, the egg secretion, one of 

 the three physiological activators, also combines with it to produce 

 a compound soluble in water. 



According to this view, then, the resting egg contains enzymes 

 which control metabohsm, unsaturated fatty acid which inhibits 

 enzyme action, and lipolysin, which reacts with the unsaturated 

 fatty acid to make it innocuous. We can conceive that the rela- 

 tive amounts of these substances may change from time to time 

 in the same egg and may differ in different eggs. If there is more 

 than sufficient fatty acid present to combine with all the lipolysin, 

 the surplus will inhibit the action of the enzymes and the egg 



