OCTOBEB 21, 1910] 



SCIENCE 



565 



Professor Edward Hull, of England, and Dr. 

 Fridjof Nansen, of Norway. 



J. W. Spencer 

 Stockholm, 

 August 24, 1910 



SPECIAL ARTICLES 

 ' THE PERMEABILITY AND CYTOLYSIS OP EGGS 



The question as to whether cells may 

 change in their permeability to various sub- 

 stances and the bearing of these changes on 

 vital phenomena, in particular the develop- 

 ment of the egg, has excited much discussion 

 of late. My own experiments (at Tortugas 

 and Woods Hole) have been directed toward 

 determining the permeability of sea-urchin's 

 eggs for some one substance and the effect of 

 certain substances in altering the permeability 

 of the egg for this substance. Sodium hydrate 

 was chosen for the purpose because its en- 

 trance may readily be indicated after staining 

 the cells in neutral red. This dye, red in 

 neutral and acid solution, becomes yellow in 

 alkaline solution. 



Since the classic researches of Pfeffer it has 

 been well known that plant cells will take up 

 and concentrate in their sap vacuoles, certain 

 dyes, notably methylene blue, from very dilute 

 solutions. In some cells the dye is precipi- 

 tated as fine blue granules which Pfeffer 

 proved to be a compound formed with tannic 

 acid. In the leaf cells of Elodea the dye 

 remains in solution yet becomes more concen- 

 trated than without. This gives the appear- 

 ance of a diffusion of the dye into the cell 

 against a concentration gradient, which is of 

 course an impossibility. The dye must be 

 changed within, but " the precise character of 

 the still soluble combination in which pigment 

 accumulates in the cell sap of Trianea, Lemna, 

 Elodea, etc., is as yet unknown.'" A clue as 

 to the nature of the condition in which the 

 dye exists in the ceU is obtained by staining 

 with neutral red. In tap water a dilute solu- 

 tion is brick red, indicating that a small 

 amount of the dye is present in the alkaline 

 yellow condition, the undissociated molecule 

 (ROH), on the theory of indicators. But 



' Pfeffer's " Plant Physiology," Vol. I., p. 94, 

 1900. 



in the Elodea cells it is always bright red in 

 color. This suggested that within the cells the 

 neutral red existed in the acid or dissociated 

 (RCl) condition which was unable to pass out. 

 That this view is correct can be easily shown 

 by placing Elodea leaves in tap water con- 

 taining neutral red plus just enough acid to 

 convert all the dye into the acid condition 

 without injuring the cells themselves. Not a 

 cell stains. Thus the protoplasts " select " 

 only the undissociated molecules of basic dyes 

 from a solution. Within the cell these are 

 practically completely dissociated and unable 

 to pass out, giving the appearance of diffusion 

 against a concentration gradient. Exactly 

 the same conditions hold for methylene blue, 

 only there is no difference in the color of the 

 dissociated and undissociated elements. 



Sea-urchin eggs are also capable of concen- 

 trating neutral red from very dilute solutions, 

 but the manner of retaining the dye is very 

 different, although the conditions of entrance 

 are the same. No neutral red can enter sea- 

 urchin eggs from dilute acid sea water in con- 

 centrations which do not coagulate the egg. 

 As soon as the eggs do coagulate they stain 

 but in a different manner from the normal 

 eggs. In the latter the dye is taken up (com- 

 bined?) by granules distinguishable from the 

 yolk granules, in that they always pass to the 

 distal pole of the egg on centrifuging, whether 

 first stained and then eentrifuged or first cen- 

 trifuged and then stained. They are present 

 in the fertilized as well as the unfertilized egg 

 (Toxopneustes), but the rate of staining of 

 these granules is much more rapid in the for- 

 mer than the latter. I would attribute this 

 to the rate of entrance of the dye and can 

 therefore confirm for neutral red what Lyon 

 has recently found for methylene blue. 



If red-stained sea-urchin eggs are placed in 

 hyperalkaline (100 c.c. sea water + 1-3 c.c. 

 w/10 NaOH) sea water they retain their red 

 color for several hours. When killed by 

 chloroform-saturated sea water, the alkali al- 

 most instantly enters and turns the red to 

 yellow. It may be shown that the color 

 change is independent of the swelling of the 

 egg caused by chloroform, for the penetration 



