MEMBRANE FORMATION AND CYTOLYSIS 177 



The following example will illustrate this. Four drops of a 

 weak solution of saponin in sea-water were added to 5 c.c. of 

 sea-water with eggs. Membrane formation started after five 

 minutes, and three minutes later all the eggs possessed mem- 

 branes. The eggs were then washed in 200 c.c. of sea-water that 

 was free from saponin, and this washing was repeated four times. 

 They were next put into 50 c.c. sea-water +6. 5 c.c. of 2| m NaCl. 

 Portions of the eggs were replaced in sea-water after 15, 25, 33, 

 45, 55, 65, and 93 minutes, respectively. All eggs that had been 

 only 15, 25, or 35 minutes in hypertonic sea-water disintegrated. 

 A few of the eggs that had been 45 minutes in the hypertonic 

 solution developed into larvae, while 10 per cent, 60 per cent, 

 and 80 per cent of larvae were given by the eggs that had been 

 55, 65, and 93 minutes, respectively, in the hypertonic solution. 



As a control I treated eggs in the same manner after mem- 

 brane formation by means of butyric acid; similar results were 

 obtained. The life duration of the butyric-acid larvae was, 

 however, longer than that of the saponin larvae. 1 



We know that solanin and digitalin possess haemolytic 

 properties like saponin. It can also be shown that sea-urchin 

 eggs that have been induced to form membranes by these 

 agencies can be caused to develop into larvae. 



The cytolytic effect of bile salts is well known. A mixture 

 of sodium glycocholate and taurocholate was dissolved in water. 

 Membrane formation soon followed when eggs were placed in 

 such a solution. The membrane was formed while the eggs 

 were still in the solution of the bile salts, just as in the case of 

 the saponin solution. Membrane formation was rapidly fol- 

 lowed by cytolysis of the egg. But if the eggs were transferred 

 to normal sea-water in time, cytolysis did not supervene. On 

 being transferred at the right time (i.e., after a membrane had 

 formed, but before they had all cytolyzed) from the solution of 



i Loeb, "Ueber die Hervorrufung der Membranbildung uiid Entwicklung 

 beim Seeigelei durch Blutserum von Kaninclien und durch zytolytisclie Agcnzien," 

 Pfliiger's Archie, CXXII, 199, 1908. 



