492 



ALVALYN E. WOODWARD 



formed on these eggs were remarkable in resembling the mem- 

 branes on eggs fertilized with sperm more closely than those on 

 the usual parthenogenetic eggs — another reason for the belief 

 that iodine reacts with the normal inhibitor and so permits the 

 normal activator to function. 



Arbacia eggs, like those of Asterias, become resistant to ferti- 

 lization toward the close of the breeding season. Their fertility 

 may likewise be increased by allowing them to stand in dilute 

 iodine solution ten minutes before insemination. It should be 

 noted that iodine treatment, like any other form of 'doctoring,' 



TABLE 16 

 The parthenogenetic effect of iodine 



does not improve eggs that are already fairly normal, like those 

 in the last column of table 17. 



In this connection it is interesting to recall the experiment of 

 E. P. Lyon and L. F. Shackell (10). They found that iodine, 

 as indicated by the starch reaction, disappeared more rapidly 

 from sea-water in the presence of unfertilized eggs than of eggs 

 which had been fertilized. From this they concluded that the 

 unfertilized eggs are more permeable to iodine than the fertilized. 

 In the light of my own experiments, it seems more probable that 

 the unfertilized eggs contained more unsaturated fatty acid with 

 which the iodine might combine. 



