62 



Scientific Proceedings (47). 



the action of the serum is succeeded by cytolysis or may even be 

 accompanied by marked agglutination of the eggs, thus confirming 

 Loeb's view that the formation of a fertilization membrane is 

 essentially a phenomenon of incipient cytolysis. 



3. The cytolytic (and fertilizing) action of ox serum (rendered 

 isotonic to sea water) upon sensitized sea-urchin eggs is enhanced 

 by dilution with sea water, a maximum potency being attained at 

 a dilution of about 1/16. 



4. I find that the increase in the cytolytic activity of serum 

 which accompanies dilution is attributable to the fact that the 

 proteins in serum in some degree inhibit membrane-formation. 

 The inhibitory effect of the proteins becomes negligible if these 

 are sufficiently diluted. If a protein (e. g., gelatin or ovomucoid) 

 be added to diluted serum its cytolytic activity is greatly di- 

 minished or even abolished. 



5. The inhibiting action of proteins upon cytolysis is due to 

 the fact that they penetrate the outer membranes of the cells 

 either with difficulty or not at all, so that by their osmotic tension 

 they prevent the taking up of water by the cells. This is well 

 illustrated by the fact that the order of efficiency of different pro- 

 teins (the mixed proteins of serum, gelatin, "insoluble" serum 

 globulin, casein and ovomucoid) is the reverse order of their 

 ability to pass through the pores of a porcelain filter. The follow- 

 ing table shows the concentrations of the various proteins inves- 

 tigated which were observed to permit or inhibit the formation of 

 spherical membranes after treatment of the eggs with 50 c.c. of 

 sea water containing 2% c.c. of N/10 butyric acid for 2^/2 minutes 

 and then transferring them to 50 c.c. of the protein solution in 

 sea water: 



Highest Observed Concentration Lowest Observed Concentration 

 which Permits the Formation which Prevents the Forma- 



of a Spherical Membrane tion of a'Spherical Mem- 



within 1% Hours. brane within 1% Hours. 



Protein. Per Cent. Per Cent. 



The mixed serum proteins 3.7 7.4 



Gelatin 1.0 2.0 



"Insoluble" serum globulin 0.3 0.6 



Casein 0.25 0.5 



Ovomucoid 0.125 0.25 



6. It will be observed that the power of the mixed proteins of 

 serum to inhibit membrane-formation is very strikingly inferior 



