EFFECT OF FOREIGN BLOOD 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 solution immediately 

 after membrane formation. But the sipunculid serum does not 

 cytolyze the egg, at least not in the concentration necessary to 

 produce membrane formation. 



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 efficacy 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 

 2J m NaCl solution (1 c.c. of the 2J m NaCl solution was 

 added to 6.5 c.c. of the serum). 



