FERTILIZATION REACTION IN ECHINODERM EGGS. 27 1 



substances liquefy the Arbacia egg. It is thus evident that the 

 response to membrane-elevating substances, so far as tested, is 

 not equivalent to the response to sperm. 



The usual butyric acid treatment yields, after return to normal 

 sea-water, a percentage of eggs with membranes of normal ap- 

 pearance equal to that produced by sperm. But in such eggs, 

 also, the normal gelation appears to be lacking. 



The majority of the eggs treated with membrane-elevating 

 substances such as ether and distilled water undergo a change 

 designated by Loeb as cytolysis. 1 This condition is sufficiently 

 described in Loeb's book ('13). The eggs are much expanded and 

 transparent. It appears from Loeb's description ('13, p. 188) 

 that he regards this cytolysis to consist in an absorption of fluid 

 followed by a liquefaction of some of the egg contents. It can 

 readily be shown by the needle that this conception of cytolysis 

 is erroneous. Cytolysis is not a liquefaction of the egg contents; 

 it is a complete and irreversible coagulation. This fact was 

 discovered by Heilbrunn ('15) and the increased viscosity of 

 cytolyzed eggs was also noted by Goldfarb ('18). When cyto- 

 lyzed eggs are punctured with a needle, a small amount of watery 

 fluid generally escapes (this is probably water which passes in 

 from the outside when the membrane expands) but the egg 

 material itself will no longer flow. It is completely solidified and 

 can be cut into pieces with a needle. 



The coagulation - caused by membrane-elevating solutions is 

 entirely different from the normal gelation attendant on fertiliza- 

 tion. The cytolytic change is an irreversible lethal change in 

 which the egg colloids are precipitated out in a coagulated mass. 

 The viscosity of the cytolyzed egg is very much greater than 

 that of the normally fertilized egg at any time from fertilization 

 to the first cleavage. The normal gelation on the other hand is 

 a reversible physiological process in which there is no such pre- 

 cipitation of colloids. 



The cause of cytolysis appears to be as follows. Since after 



1 My remarks refer only to the "white" cytolysis of Loeb. 



2 The term coagulation can of course be used to designate any marked increase 

 in viscosity. It seems preferable to me, however, to confine the term to an irrevers- 

 ible separation out of colloids and to use the term gelation to designate reversible 

 physiological increases in viscosity. 



