THE PERMEABILITY OF THE EGG MEMBRANE. 387 



longed in the absence of calcium salts and especially in a medium 

 of Na.,So 4 . 



6. These experiments and those of Loeb and Morgan seem to 

 indicate that the relative surface tension of the egg and of the 

 sperm is one important factor governing fertilization. 



MARINE BIOLOGICAL LABORATORY, 



WOOD'S HOLL, MASS., August, 1905. 



