332 RALPH S. LILLIE. 



creases irritability; the presence of more lipoid-solvent renders 

 a change of permeability difficult, 1 hence the protective or an- 

 aesthetic action; while concentrated solutions of lipoid-solvents 

 disrupt the membrane and produce cytolytic or irreversible 

 alterations in the cells; hence such substances in higher concen- 

 trations are markedly toxic. 



On the assumption that lipoid-solvents influence the plasma 

 membranes of egg cells in essentially the same manner as those of 

 irritable tissues, the above action of ether on abnormal egg cells 

 becomes more readily intelligible; it falls, in fact, into the same 

 essential category \vith the facts just cited. There is a close 

 analogy between the stimulation of irritable tissues and the initia- 

 tion of cleavage in egg cells; the primary or critical change in 

 both cases appears to be a temporary and reversible increase in 

 the permeability of the plasma membrane, with accompanying 

 changes in the electrical polarization of the latter. 2 This analogy 

 suggests that the irresponsive condition of the above "over- 

 ripe" starfish eggs is essentially the symptom or expression of an 

 abnormal condition of the plasma membrane. Apparently the 

 latter has in these eggs become abnormally resistant to changes of 

 permeability; hence the eggs are irresponsive to the spermato- 

 zoon (whose primary action is to increase permeability); hence 

 also they show heightened resistance to cytolytic action which 

 also depends on increase in surface permeability; this is shown 

 by the slowness with which they undergo the typical post- 

 maturational cytolysis, and also by their increased resistance to 

 pure isotonic sodium chloride solution. If this interpretation is 

 correct, the favorable action of weak ether solution consists es- 

 sentially in altering the plasma membrane and rendering it more 

 susceptible to the action of permeability-increasing (and hence 

 depolarizing) agencies i. e., more irritable, on the above-men- 

 tioned analogy with irritable tissues. Through this means the 

 plasma membrane is restored to an approximately normal condi- 



1 This is very clearly shown in the larva of Arenicola; cf. the paper just cited, 

 p. 380 ff. 



2 I have discussed the probable basis of this resemblance at some length in an 

 earlier paper in the BIOLOGICAL BULLETIN, 1909, Vol. 17, pp. 20 ff. The title of 

 Loeb's recent book, "Entwicklunjjserregung des tierischen Eies," also emphasizes 

 this analogy. 



