Penetration of Marine Tissues by Alkali. 139 



Further evidence that the egg increases in permeabiHty immediately 

 after fertihzation is furnished by McClendon." He found that the elec- 

 trical conductivity of the sea-urchin egg is increased after fertilization, thus 

 showing that its permeability is increased. 



A similar result may be obtained by the plasmolytic method. ^^ Fertilized 

 eggs are plasmolyzed more readily than unfertilized by a molecular solution 

 of cane sugar. This is due to the fact that the salts diffuse out of fertilized 

 eggs more rapidly, the osmotic pressure within falls more rapidly, and plas- 

 molysis occurs more readily. 



Yet another fact indicates that the surface of fertilized eggs has under- 

 gone a marked change. They are entered more readily by NaOH.^^ In this 

 particular case we may say that the resistance to the entrance of alkali has 

 decreased, using the word resistance, as before, to indicate that the NaOH 

 enters only after modifying the normal impermeability of the surface. 



Trondle,^^ and also Lepeschkin,^" using the plasmolytic method, have 

 found that the permeability of plant cells for salts and sugar increases in 

 the light. The increased permeability has an adaptive significance in that 

 the sugar formed by photosynthesis may be more rapidly removed and 

 photosynthesis itself thereby favored. 



PENETRATION RATE AND CHANGES IN FUNCTIONAL ACTIVITY. 



Under this head are classed the cases in which the rate of penetration of 

 the substance is reduced to zero, i. c, cases in which marked functional or 

 structural changes appear, while we have no evidence that the substance 

 enters the cell at all. The obvious conclusion is that it produces the effects 

 observed by acting on or combining with the cell-surface itself, and affords 

 excellent proof of the important role played by the surface in all activities. 



It has long been known that muscles lose their irritability in isotonic 

 solutions of potassium salts. Overton^^ showed that the muscle might 

 remain in the potassium salt solution for days without change of volume, 

 so that the potassium salt could not have entered and its effect in changing 

 irritability must have been a surface action. 



Warburg22 showed that the oxygen consumption of the egg was greatly 

 increased in the presence of dilute NaOH, although the NaOH did not enter; 

 yet NH4OH could enter readily and in concentrations containing too few OH 

 ions to affect to any marked extent the oxygen consumption. Neutral red 

 is therefore a more delicate test for OH ions than increased rate of oxidation. 

 Here is unequivocal evidence that a chemical process in a cell can be affected 

 by a substance which does not enter the cell at all. 



In my earlier paper I have shown that initiation of cell division in sea- 

 urchin eggs, stoppage of ciliary movement and cytolysis of ParamcBcium, 

 and stoppage of protoplasmic rotation in Elodea might be brought about 

 before any appreciable amount of NaOH had entered the cells. 



" McClendon, J. F. Amer. Jour. Physiol., vol. 27, p. 240. 1910 



•8 Harvey, E. N. Science, n. s., vol. 32, p. 56s. 1910. 



" Trondle. Ber. d. deutsch. hot. Ges., vol. 27, p. ^i, 1909; and Jahrb. f. wiss. Bot., vol, 48, p. 171, 1910. 



*Lepeschldn. Ber. d. deutsch. bot. Ges., vol. 26a, pp. 198,231, and 724, 1908; and Beihefte z. bot. 



Zentralb., vol. 24I, p. 308, 1910. 

 »> Overton, E. Pfluger's Arch., vol. 92, p. 115. 1902. 

 *• Warburg. Loc. cit. 



