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. Lillie 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. 



