452 PROCESSES INFERRED FROM INDIRECT OBSERVATION 



gen ions and 5. Hydroxyl ions. Successive experiments have shown 

 that each of these groups of reagents may, by appropriate manipula- 



6. 7. 



FIG. 29. Formation of fertilization-membrane and cytolysis of the sea-urchin egg 

 on treatment with saponin. 1, appearance of egg when first exposed to saponin solu- 

 tion at 9.07 A.M.; 2, 3, and 4, formation of fertilization-membrane. The stage of com- 

 plete membrane-formation as depicted in 4 was reached at 9.15 A.M. (if at this stage 

 the egg is withdrawn from the influence of the saponin it can develop). Cytolysis, 5, 

 began at 9.20 A.M.; 6 and 7, advanced stages of cytolysis induced by saponin. (After 

 Loeb,) 



tion, be made to cause membrane-formation in the unfertilized sea- 

 urchin egg. The Saponins especially are extraordinarily efficient in 

 inducing this phenomenon, membranes being formed in 100 per cent. 



