2 E. E. JUST. 



with outflow of cytoplasm does not facilitate sperm entry. To off- 

 set the possibility that fixation might be a source of error, most 

 diverse fluids were used. In the living egg, in addition, it was 

 easy to see that spermatozoa do not react with fertilized eggs. 

 There is here, certainly, no evidence in support of Kohlbrugge's 

 results. 



Many experiments have likewise been made thus: Eggs are 

 lightly inseminated and at five-second intervals up to the time of 

 membrane separation are given an additional heavy insemination. 

 Such eggs fail to reveal polyspermy in higher per cent, than eggs 

 that have but one insemination. 



Thus, June 28, 1918, eggs of Echinarachnius were inseminated 

 and at five-second intervals up to time of membrane separation 

 were reinseminated. After membrane separation, the eggs were 

 gently shaken to remove the membranes; samples of these were 

 reinseminated at six, thirteen, sixteen, and twenty minutes after 

 the original insemination. Samples of these eggs were fixed in 

 corrosive sublimate-acetic two minutes after each insemination. 

 No evidence of a reaction was found in any of the sectioned 

 material. 



In addition, the bulk of the evidence (Lillie, '19) shows that 

 artificially activated eggs fail to react with sperm. 



Wilson found that fragments of fertilized eggs of Cerebratulus 

 are incapable of fertilization. Conklin has shown that the un- 

 usually large polar bodies produced by the egg of Crepidula 

 through centrifugal force do not fertilize. Since in this egg polar- 

 body formation follows insemination, Conklin's results are capable 

 of the interpretation that here, too, parts of fertilized eggs do not 

 refertilize. 



In Echinarachnius the situation is the same. If inseminated 

 eggs of Echinarachnius be gently shaken in a vial with bits of 

 broken coverslips and the fragments thus obtained be divided into 

 two lots, one of which is inseminated, the per cent, of development 

 in the two lots is the same. The insemination of these fragments, 

 even if made twenty seconds after the insemination of the intact 

 eggs, does not increase the per cent, of development. 



These observations indicate that fertilization is irreversible, eggs 



