INTRODUCTION 9 
in order to counteract the injurious secondary effects of 
membrane formation. If the eggs are not removed from the 
saponin solution immediately after membrane formation, 
cytolysis supervenes in a few minutes. Similar results are 
obtained with soap. A short exposure of the eggs to an 
alkaline soap solution in NaCl leads to membrane formation 
(and to development if the eggs are subsequently treated for a 
short while with a hypertonic solution). A longer exposure of 
the eggs to a soap solution leads to cytolysis. 
The same behavior can be demonstrated for all cytolytic 
reagents, even those of a physical nature, as, for example, rise 
of temperature. A sufficient increase of temperature causes 
membrane formation in the unfertilized sea-urchin egg and one 
of longer duration leads to cytolysis. R. Lilhe has found that 
the eggs of starfish can develop into larvae after membrane 
formation caused by raising the temperature. Sea-urchin 
eggs are too much injured by the increase of temperature neces- 
sary for membrane formation to be able to develop. 
We know that the blood corpuscles of any species of animal 
are often cytolyzed by the body fluids of different species. In 
1907 I found that the blood of certain worms, to wit, the’ 
Gephyrea, causes membrane formation in the sea-urchin egg, 
even when greatly diluted. This power is also possessed by the 
blood of other forms, especially of mammals. This phenomenon 
is, however, not exhibited by the eggs of every female, and I 
believe that this is due to a difference in the permeability of the 
eggs of different females. Only those eggs that are permeable 
to the “lysins”’ of the foreign blood form membranes under its 
influence. If such eggs are exposed for a short while to hyper- 
tonic sea-water, after membrane formation has been produced by 
the blood, they develop into larvae. The cytolysis of these eggs 
with foreign blood is impossible, or proceeds only very slowly; 
this, i think, is due to the fact that the fertilization membrane 
prevents the further diffusion of the “‘lysins” into the egg. 
