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, 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 250c.c. 0.55m Nal; when transferred to sea-water all 
formed membranes. Eggs left for five minutes in 250 c.c. 
0.55m Na!l+15c.c. m/2 CaCl, practically all remained normal 
when put back into sea-water. The solution containing Ca is, 
-however, not entirely ineffective, simce some eggs treated with 
this solution may deveiop 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,. 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 NaI and 
NaCNS are slightly soluble in the egg and owe their efficiency 
to this fact. That Ca and bivalent metals in general inhibit 
eytolysis 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 zweiwertigen 
Metallen,’’ Biochem. Zeitschr., V, 351, 1907; II, 81, 1906. 
