ANTAGONISM BETWEEN SALTS AND ANESTHETICS 613 



selective semi-permeability, that have led to its distinction from 

 the more internal protoplasm. Conceived in this way, it corre- 

 sponds closely to what morphologists designate as the cortical 

 region of the egg, or at least to the most external layer of this 

 region. 



Changes in this region form a highly characteristic accompani- 

 ment of fertilization in many if not in all eggs; associated with 

 these changes is a marked temporary increase in the general 

 permeability of the surface-layer. The relation of these surface- 

 changes or cortical processes to the initiation of cell division 

 and development is evidently a critical one.-*^ Once they are 

 accomplished the developmental mechanism, hitherto held in 

 check, resumes operation and^ — provided external and other 

 conditions are favorable — continues its course automatically 

 to the adult stage. It is clear, from the diversity of the con- 

 ditions that may initiate development, that some process specific 

 to the egg and quite independent of the nature of the activating 

 condition forms the primary event in fertilization. The sper- 

 matozoon or the parthenogenetic agent in some way removes the 

 hindrance to this process. What the nature of the latter is 

 may be partly inferred from the results of recent experiments 

 on the physiology of fertilization. The observations described 

 in this paper support the view that some change in the cortical 

 region of the egg-protoplasm, beneath the most external semi- 

 permeable layer of plasma-membrane proper, forms the initial 

 stage of the fertilization-process. The immediate surface of the 

 egg has semi-permeable properties relatively to most water- 

 soluble lipoid-insoluble substances, and apparently must under- 

 go increase of permeability in order that such a salt as Nal or 

 KCNS may produce its characteristic effect. As already said, 

 it is uncertain whether the salt acts by entering and then affecting 

 directly the state of the colloids in the cortical region, or whether 

 it acts without entrance, possibly by altering the electrical polar- 

 ization of the plasma-membrane. It seems probable, however, 

 from the general effectiveness of lipoid-alterants, that some 



2" Cf. F. R. Lillie, on The cortical changes in the egg of Nereis. Jour. Morph., 

 1911, vol. 22, p. 361. 



