STUDIES IN ARTIFICIAL PARTHENOGENESIS. 329 



Some Cumingia eggs were placed in a 0.04 per cent, solution of 

 potassium cyanide, five minutes after they had been fertilized. 

 The solution was prepared by diluting 5 c.c. of 2 per cent. KCN 

 up to 250 c.c. with sea-water. Solution and eggs were kept in a 

 glass-stoppered weighing-tube to guard against evaporation of 

 the cyanide. Under these conditions practically all of the 

 fertilized eggs formed the first polar body. Actual count with- 

 out turning over the eggs, showed 24/50. 



On the other hand it might be thought that all types of cortical 

 change produce an increase of permeability. In recent years 

 various observers have claimed that the sea-urchin egg under- 

 goes an increase in permeability either after fertilization or 

 after artificial membrane elevation. These observers have en- 

 deavored to show: (i) An increased penetration of dyes, (2) a 

 drop in electrical resistance, (3) a more rapid passage of water 

 into or out of the cell. 



When fertilized sea-urchin eggs are placed in dilute solutions 

 of methylene blue, they stain more rapidly than do unfertilized 

 eggs, according to Lyon and Shackell, '10. Runnstrom, 'n, 

 obtained similar results with methylene blue although not with 

 neutral red. The experiments of Lyon and Shackell are fre- 

 quently cited and are always taken to indicate an increased 

 permeability after fertilization. 1 When unfertilized and fertilized 

 Cumingia eggs are placed in dilute solutions of methylene blue 

 or neutral red, the unfertilized eggs take up the dye just as 

 rapidly as do the fertilized eggs. 



Fertilized and unfertilized eggs were put into Syracuse dishes 

 containing methylene blue solutions of various strengths. From 

 time to time the eggs were examined over a light and over a dark 

 background, and under the microscope. The color of faintly 

 stained eggs can be much better observed with the naked eye 

 than with the microscope. A more accurate method of deter- 

 mination would involve the use of a colorimeter but the method 

 used was sufficient to show that no marked increase of permeabil- 

 ity occurred. The dilutions of the dye were made up from a 0.5 

 per cent, solution of Griibler's "Methylenblau rectif. nach 



1 They might however indicate nothing more than an increased affinity for 

 dyes on the part of the cytoplasm. Such changes in staining properties are 

 common enough, especially after changes in the colloidal state. 



