178 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 
bile salts to normal sea-water, they did not develop if left 
therein. But some of them did develop into larvae after a 
subsequent short exposure to a hypertonic solution. The 
eggs were more harmed by membrane formation with bile salts 
than by membrane formation with saponin. 
In both cases only those eggs developed, after a Sige treat- 
ment with hypertonic sea-water, which had formed membranes, 
a fact which is also true of eggs treated with a fatty acid.! 
3. In 1905 I started experiments on membrane formation in 
the egg by means of soaps; but by chance these experiments 
led to no results. The experiments were resumed a few years 
later with positive results. For since soaps are good cytolytic . 
agents, one could postulate a definite result from these experi- 
ments. I will first briefly portray the cytolytic effect of the 
soaps and then discuss their developmental effect. 
As soap is precipitated by calcium, it was necessary to 
dissolve it in m/2 NaCl solution, instead of in sea-water. Now 
when the unfertilized eggs of S. purpuratus (after being freed 
from sea-water by washing in m/2 NaCl) are placed in 50 c.c. 
of neutral m/2 NaCl+2 ¢c.c. m/10 sodium oleate, neither mem- 
brane formation nor cytolysis occurs as a rule in that solution. 
The eggs only become angular. But if they are placed after a 
few minutes in sea-water, a large number of them form mem- 
branes at once, which in a few eggs is followed by cytolysis. 
The longer the eggs remain in the soap solution, the greater 
becomes the percentage forming membranes and cytolyzing 
after transference to ordinary sea-water. For the eggs of many 
sea-urchins the addition of 2 ¢.c. of sodium oleate to 50 c.e. of 
NaCl is too little, and about 3 ¢c.c. of soap must be added. 
Why does the soap solution not cause membrane formation 
until after the egg has been replaced in sea-water? The reason 
is that it is the sea-water which causes the membrane forma- 
tion as a result of its alkaline reaction. The soap solution either 
1 Loeb, op. cit. 
5 OO TORR 
