FERTILIZATION REACTION IN ECHINARACHNIUS PARMA. 



21 



Series 5: 

 (12:00 M.) 



Controls : Uninseminated in sea-water — 1 per cent, cytolysis. 

 Inseminated in sea- water 99 -f- cleavage. 



It is clear from this experiment that eggs exposed to a dilution 

 of sea-water during membrane separation cytolyze in slightly 

 higher per cent, than eggs inseminated in the dilution. Similarly, 

 eggs inseminated in normal sea-water and exposed before or after 

 membrane separation cytolyze in slightly lower per cent, than eggs 

 exposed during membrane separation. The cleavage per cent, of 

 surviving eggs is about the same. 



If we hold that membrane separation is a criterion of fertiliza- 

 tion, then eggs inseminated in a given dilution of sea-water are 

 fertilized whether they cleave or not. This admittedly is not a 

 strong case, but it gives some support to the position that the fer- 

 tilization reaction is practically instantaneous. It is not fertiliza- 

 tion that is checked by the action of dilute sea-water, but the re- 

 actions which set up by fertilization lead to cell division. 



