MEMBRANE FORMATION AND CyYTOLYSIS 177 
The following example will illustrate this. Four drops of a 
weak solution of saponin in sea-water were added to 5.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. sea-water+6.5 c.c. of 23 m NaCl. 
Portions of the eggs were replaced in sea-water after 15, 25, 33, 
45, 55, 65, and 93 minutes, respectively. ll 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 larvaefwhile 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.! 
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 
1 Loeb, ‘‘Ueber die Hervorrufung der Membranbildung und Entwicklung 
beim Seeigelei durch Blutserum yon Kaninchen und durch zytolytische Agenzien,”’ 
Pfliiger’s Archiv, CX XII, 199, 1908. 
