IODINE AS A PARTHENOGENETIC AGENT.' 



359 



near the close of the breeding season, when the eggs vary greatly 

 in their fertilizing power and their sensitiveness to reagents. 

 It is probable that the strength found best for this season will 

 prove too great for the more sensitive eggs in the height of the 

 season July, for instance. 



Table II. is a summary of Table I., giving the average number 



TABLE II. 



SUMMARY OF TABLE I. 



of cleavages plus membranes obtained by each method of treat- 

 ment. A number in italics is the result of one experiment, 

 rather than the average of several. There is a remarkable uni- 

 formity in the percentages obtained by treating the eggs for 

 varying periods of time. For instance, whether exposed for 

 two and one half or fifteen minutes, or for some intermediate 

 period, to one eighth saturated iodine, the eggs gave percentages 

 between 26 and 28. The indication is that the iodine enters the 

 egg immediately and affects it immediately to its full extent. 

 One would expect this result if it acted by combining chemically 

 with something in the egg. While length of exposure has no 

 effect, varying the strength of iodine used causes great variation 

 in the result. This indicates a secondary, non-initiatory or 

 injurious effect due to the excess. The optimum results usually 

 followed treatment of 2 c.c. eggs in sea-water with 2 c.c. of one 

 fourth or one eighth saturated iodine solution. While hyper- 

 tonic after treatment was nearly always beneficial, in most cases 

 the effect was so slight as to be negligible. 



It may be recalled that membrane formation and subsequent 



