334 



L. V. HEILBRUNN. 



In hypertonic solutions fertilized Cumingia eggs lose more 

 water than do the unfertilized. The water does not merely 

 leave the eggs more rapidly, more of it passes out and the osmotic 

 equilibrium is different in the two cases. This is shown by an 

 experiment in which fertilized and unfertilized eggs were placed 

 in solutions prepared by adding i part of 2 M MgSO 4 to 2 parts 

 of sea-water. Measurements were made as in the previous 

 experiment. The results are given in Table III. 



TABLE III. 



DIAMETERS OF FERTILIZED AND UNFERTILIZED EGGS IN 30 c.c. 



2M McSOj + 60 c.c. SEA-WATER. 

 Average Diameter of 10 Unfertilized Eggs in Sea-water 6i.~4 n- 



The above table requires a little explanation. Some of the 

 eggs, usually the unfertilized ones, became slightly flattened at 

 one pole while in the hypertonic solution. These eggs therefore 

 had a slightly smaller volume than their diameter would indicate. 

 In order to show the extent of the flattening a second measure- 

 ment was taken from the flattened pole to the opposite pole of the 

 egg. This second measurement is in every case shown in 

 parentheses. Another point also needs explanation. The ferti- 

 lized eggs measured in the second column had lost so much water 

 in the hypertonic solution that their cytoplasm was coagulated 

 and had in most cases begun to shrink away from the vitelline 

 membrane. This shrinkage was most pronounced in the third 

 and fourth eggs measured and this accounts for the very small 

 size of these eggs. 



