THE PHYSIOLOGY OF CELL DIVISION 25 



of this general theory from observations on the pigmented larvae 

 of Arenicola, where stimulating solutions, for example, 0.55m 

 NaCl, cause visible increase of permeability; stimulation and 

 permeability-increase show an unmistakable parallelism in this 

 organism, and both processes are simultaneously decreased or 

 prevented by the same agencies, such as calcium or magnesium 

 salts and anesthetics.^ 



In fertilization also the primary change is a surface-change, 

 which almost certainly involves an increase in the permeability 

 of the plasma membrane. Loeb's researches have demonstrated 

 the general effectiveness of cytolytic substance in initiating cleav- 

 age in sea-urchin eggs.^ Pure solutions of neutral sodium and 

 potassium salts have the same effect, which is the more marked 

 the more energetic the permeability-increasing action, and is 

 inhibited by salts like calcium or magnesium chloride which 

 check or prevent this action.^ The egg-cell immediately after 

 normal fertilization shows increased electrical conductivity^ and 

 increased permeability to substances like sugar and alkali,* as 

 well as to its own pigment,^ All of these facts indicate that the 

 fertilization-process involves an initial increase in permeability; 

 such a change ought theoretically to be accompanied by a change 

 in the electrical polarization of the membrane, similar to that 

 which, on the membrane theory, conditions the action-current 

 in irritable tissues; and Miss Hyde's observations on Fundulus 

 eggsi" indicate that this is in fact the case. A depolarization- 

 process thus probably accompanies the initial stage of fertiliza- 

 tion, as well as of stimulation, and it is highly probably that 

 it forms the critical or initiatory event in this process also. 



'' I have discussed this subject in fuller detail in a recent paper in the American 

 Journal of Physiology, 1911, vol. 28, p. 197. 



* J. Loebj.Chemische Entwicklungserregung des tierischen Eies, and his num- 

 erous earlier papers there cited. 



^ R. S. Lillie, American Journal of Physiology, 1911, vol. 27, p. 289. Journal 

 of Morphology, 1911, vol. 22, p. 695. 



^ McClendon, American Journal of Physiology, 1910, vol. 27, p. 240 



8 E. N. Harvey, Science, N. S. 1910, vol. 32, p. 56.5. .lournal of Experimental 

 Zoology, 1911, vol. 10, p. 547. 



» Lyon and Shackell, Science, N. S., 1910, vol. 32, p. 249. 



1" I. H. Hyde American Journal of Physiology, 1904, vol. 12, p. 241. 



