IODINE AS A PARTHENOGENETIC AGENT. 



ALVALYN E. WOODWARD AND FLORENCE S. HAGUE. 



In the course of some experiments with Arbacia eggs at Woods 

 Hole last summer, it was noted that, if a little iodine was added 

 to the eggs in sea-water, regular fertilization membranes appeared 

 on a large number. This led to an attempt to find the optimum 

 conditions for the use of this reagent in parthenogenesis. 



The stock solution used was made by dissolving iodine crystals 

 in sea- water to the point of saturation. This stock solution 

 was diluted with sea-water as shown in the tables. 



Some of the females were stimulated to shed their eggs into 

 watch glasses. In other cases, the ovaries were removed and 

 shaken in sea-water to loosen them. Whichever method was 

 followed, the eggs were washed and allowed to settle. The 

 supernatant water was poured off, the eggs evenly mixed in 

 fresh sea-water, and 2 c.c. of the mixture put into each of a 

 series of watch glasses. To each of these an equal volume of 

 iodine solution was added, for a given length of time. Some of 

 the eggs were then put into finger-bowls containing about 50 

 c.c. of sea-water. Others were treated for 20 minutes with 

 hypertonic sea-water (50 c.c. sea-water + 8 c.c. 2.5 N NaCl). 

 At the end of that time, the solution was drawn off and the eggs 

 transferred to finger bowls of sea-water. With each lot of eggs, 

 three controls were made, one fertilized with sperm, one unin- 

 seminated, and one uninseminated but treated with hypertonic 

 sea-water. 



Table I. shows the percentage of membranes and cleavages 

 produced by varying the strength of the solution and the length 

 of exposure. To obtain these averages, over two hundred eggs 

 were counted in each case. 



It will be noted that there is great variability in the results 

 with different batches of eggs. This may be explainable from 

 the fact that the experiments were carried on during the last 

 two weeks of August and the first week of September, a period 



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