78 



Papers from the Department of Marine Biology. 



VARIATIONS IN JELLY LAYER. 



With India-ink solutions as used by F. Lillie, the jelly layer surround- 

 ing the egg is rendered distinctly visible and the eggs with the thick 

 jelly coating may be readily distinguished from those with either very 

 thin coats of jelly or no jelly. Table 3 gives the percentage of eggs 

 with jelly envelope for each female. Counts of not less than 100 eggs 

 were made. The number of eggs with jelly layers is usually very large: 

 8 out of 14 females had over 90 per cent with jelly layers; in experiment 

 6/28, both females had 100 per cent; in experiment 6/27 they varied from 



Table 3. — Variation in size and jelly of eggs of different feinalcs of Hipponoe and Arhacia. 



Hipponoe. 



Date. 



No. 



Age 



of 

 eggs 



Diameter of eggs in eye-piece micrometer readings. 



21 20.5 20.0 



19.5 19.0 18.5 18.0 17.5 17.0 16.5 



Percentage 



of eggs 

 with jelly. 



6/25 



6/26 



6/27 



6/28 



Total. 



hours. 

 2 

 2 

 5 

 

 

 

 

 

 3 

 3 

 3 

 3 



10 

 3 



7 

 1 

 1 

 4 

 6 

 3 

 10 



12 

 11 

 5 

 6 

 1 

 5 



100 

 63 



100 

 86 

 95 

 99 

 90 

 96 

 89 

 83 

 80 

 100 

 100 



34 



72 



54 



16 



Arbacia. 



8/17 

 8/10 

 8/11 



8/28 



89 

 72 

 59 

 81 



80 to 96 per cent; in experiment 6/25 one female had 100 per cent, the 

 other as low as 63 per cent. It will later be shown that these varia- 

 tions in size and jelly layer in different females also serve as indices 

 of the physiologic condition of the eggs. 



Similar results were obtained for Arbacia. It became manifest that 

 one must be cautious in interpreting the results, for with high concen- 

 tration of sperm the percentage of jelly envelopes was often reduced. 

 For example, in one experiment high concentration of sperm reduced 

 the percentage of jelly by 22 per cent, 13 per cent in another, and 3 per 

 cent in a third. 



