MEMBRANE FORMATION AND CYTOLYSIS 187 



begin to segment, but sooner or later disintegrate though a 

 few may reach an early blastula stage. Such eggs are, however, 

 abnormal. But if these eggs are exposed for a short time (in 

 Lillie's experiments thirty minutes) to a hypertonic solution a 

 large number will develop. The membrane formation produced 

 by these salts had therefore the same effect as treatment of the 

 eggs with fatty acids. 



Lillie made the very interesting observation that the 

 addition of some CaCl 2 to the solution of Nal inhibited the 

 membrane formation. The following experiments illustrate this 

 result. Unfertilized eggs of Arbacia were put for five minutes 

 into 250 c.c. 0.55m Nal; when transferred to sea-water all 

 formed membranes. Eggs left for five minutes in 250 c.c. 

 0. 55 m Nal +15 c.c. m/2 CaCl 2 practically all remained normal 

 when put back into sea-water. The solution containing Ca is, 

 however, not entirely ineffective, since some eggs treated with 

 this solution may develop into larvae when afterward exposed 

 for a short time to a hypertonic solution. 



R. Lillie explains his results on the assumption that the 

 effective salts increase the permeability of the egg, and that 

 this rise in permeability is checked through the addition of 

 CaCl 2 . The primary effect is probably a cytolytic action upon 

 the cortical layer of the egg, and on this assumption the observa- 

 tions of Lillie on the membrane formation by Nal and NaCNS 

 harmonize with the observations on the action of the specifically 

 cytolytic agencies upon the egg. It is probable that Nal and 

 NaCNS are slightly soluble in the egg and owe their efficiency 

 to this fact. That Ca and bivalent metals in general inhibit 

 cytolysis by bases had been shown by the writer in 1906 and 

 1907. 1 



Herbst made in 1904 the interesting observation that 

 minute traces of silver salts cause a membrane formation in 

 the unfertilized sea-urchin egg. The following observation by 



1 Loeb, "Ueber die anticytolytische Wirkung von Salzen mit zweiwertigeu 

 Metallen," Biochem. Zeitschr., V, 351, 1907; II, 81, 1906. 



