EFFECT OF FOREIGN BLOooD AND CELL ExTRACTS 193 
the egg is exposed to the diluted sipunculid blood, membrane 
formation takes place in the presence of the blood. 
However, it is also improbable that it is due to any of 
the hydrocarbons such as benzol, toluol, and amylene, or to 
saponin or any similar glucoside. For all these substances 
lead, not only to membrane formation, but also to cytolysis 
of the egg, if it is not removed from the selution immediately | 
after membrane formation. But the sipunculid serum does not 
cytolyze the egg, at least not in the concentration necessary to 
produce membrane formation. i 
The question of the thermostability of the effective con- 
stituent of the sipunculid serum was next taken into considera- 
tion. In order to avoid the suspicion of infection with living 
spermatozoa, it had already been found necessary in these 
experiments to heat the sipunculid serum to between 50° and 
60°C. Prolonged heating at 60°C. does not decrease the 
effectiveness of the serum, nor does heating it to 70° or 80° C. 
Suddenly heating the serum to boiling-point in one case reduced 
its eficacy to one-third of its original amount. Prolonged boil- 
ing (two to three minutes) has completely destroyed the efficacy 
in all the cases hitherto observed. 
Even when the blood was heated for an hour to 60°C. it 
did not lose its effect. 
It was subsequently found that the blood and tissue extracts 
of a large number of animals had a similar effect, although 
they did not act in such a high degree of dilution. The most 
welcome observation was that the blood of mammals (rabbit, 
pig, ox, etc.) was very active, since this enabled us to under- 
take a more systematic investigation of this field. The writer 
succeeded in producing membrane formation in sea-urchin eggs 
with the blood of mammals (dog, pig, and ox). The serum 
was rendered isotonic with sea-water by the addition of a 
2m NaCl solution (1 ¢.c. of the 23 m NaCl solution was 
added to 6.5 c.c. of the serum). 
