330 L. V. HEILBRUNN. 



Ehrlich." Five minutes after fertilization some fertilized eggs 

 were placed in dishes A2 to 2 containing o.i per cent., 0.05 

 per cent., 0.025 per cent., 0.0125 per cent., 0.00625 per cent, 

 methylene blue respectively. At the same time some unfertilized 

 eggs were placed in dishes Ai to El containing similar concentra- 

 tions of the dye. After ten minutes had elapsed, the eggs in 

 Ai and A2 were navy blue, those in Bi and 62 pale blue, those 

 in Ci and C2 scarcely colored and those in Di and D2, El and 

 2 not colored at all. Obviously there was no difference between 

 the two sets of eggs. After fifteen minutes eggs in Ai and A2 

 were navy blue, those in Bi and 62 light navy blue, those in Ci 

 and C2 light blue, the unfertilized eggs in Di were a very pale 

 blue, the fertilized eggs in D2 uncolored, in El and 2 eggs were 

 still uncolored. The eggs were observed at various times, but 

 no marked changes could be observed. After an hour I thought 

 I might be able to detect a slightly deeper color in the fertilized 

 eggs in A2, 62, C2 than in the unfertilized eggs subjected to the 

 same concentrations of dye in Ai, Bi, Ci, but this was probably 

 due to the fact that the fertilized eggs were slightly more numer- 

 ous. If entrance of stain is a test of permeability, then certainly 

 there is no sharp difference in the permeability of fertilized and 

 unfertilized Cumingia eggs. The concentrations of stain used 

 in the above experiment were not injurious. Even in the most 

 concentrated of the solutions used the eggs proceeded in their 

 development and became motile larvse. A similar experiment 

 was tried with neutral red. A saturated solution of the stain 

 and 1/2, 1/4, 1/8, 1/16 saturated solutions were used. In no 

 case could any difference in permeability between fertilized and 

 unfertilized eggs be noted. 



McClendon, '10, and Gray, '16, have maintained that following 

 fertilization there is a drop in the electrical resistance of the sea- 

 urchin egg. They have interpreted this as indicating an increase 

 of permeability, although of course various other explanations 

 might be given. In the sea-urchin egg the normal process of 

 cortical change is membrane elevation, which would interfere 

 with the experiment. McClendon and Gray therefore were 

 obliged either to \vait until the eggs lost their power of under- 

 going membrane elevation or to so treat the eggs that they lost 



