360 E. Neiuton Harvey 



There remains only the most probable action, an actual com- 

 bination of the acid with some of the egg proteids, the rate of 

 formation of this compound varying with the temperature as do 

 other reactions (Qio = 2 — 3)- 



Greeley's^ results with HCl also bear out this conclusion 

 Assuming that the acetic acid actually takes part in some 

 reaction^ in the egg , which is it? Is the membrane — for there is 

 now ample evidence (to be discussed below) to show that the 

 membrane is not present before fertilization — a resultof the union 

 of CH3COOH with some egg substance? It can be definitely 

 said that this is not the case. The many substances which will 

 produce membranes are so diverse, chemically, that it is incon- 

 ceivable they should all combine to form the same substance 

 (membrane) or even by their presence bring about its formation. 

 It is obvious that heat and mechanical agitation could not act 

 in this way. The membrane is all ready to be formed yet is pre- 

 vented from so doing by something. It forms only another 

 example of the so-called "stimulus reactions," which have been 

 compared to the setting off of a charge of gunpowder by a spark. 

 The change which "sets off" the membrane formation as well as 

 the reactions into which I believe the acetic acid enters will be 

 discussed in the second division of this paper. 



II. MECHANISM OF MEMBRANE FORMATION 



I shall first propose an explanation, of how a membrane may 

 be conceived to form about a system of interacting substances, 

 (as an egg), and then discuss somewhat more fully various facts 

 connected with its actual production. 



As observed in the living egg, almost immediately (i| to 3 

 minutes) after the addition of sperm the membrane substance 

 becomes separated from the egg surface by spaces. These spaces 

 fill with a fluid, unite and enlarge, thus pushing out the membrane 



2 Greeley: A. W. Biol. Bull., iv, 1902--5, p. 124. Greeley did not interpret his results with refer- 

 ence to chemical action. 



' Reaction is used throughout tliis paper in the same sense as in chemistry. 



