^66 E. Newtoti Harvey 



III. CHEMICAL NATURE OF THE MEMBRANE 



Experiments were also undertaken to determme the composi- 

 tion of the fertihzation membrane. Arbacia eggs were used. 



Their membranes are insoluble in //;KOH and NaOH even 

 on short boiling, although the eggs become entirel\- colorless only a 

 few granules being visible. On prolonged boiling and evaporation 

 when the strength of the alkali must approach 2h m, the mem- 

 branes dissolve or at least become so broken up as to be invisible. 



In cold concentrated H2SO4, the membrane is insoluble while 

 the egg substance first chars reddish brown, later becoming 

 entirely invisible so that only the spherical fertilization membrane 

 is apparent. Unfertilized eggs without membranes dissolve 

 entirely in concentrated H2SO4. 



In concentrated HCl there is no solution of the membrane. 

 The egg contents become a clear shrunken granular mass. Eggs 

 in the two cell staae show the division between the blastomeres 

 as a clear line. Concentrated HNO3, NH^OH and glacial acetic 

 acid act like HCl. 



I was unable to demonstrate any proteid in the membrane by 

 the xanthoproteic test although this may be due to its thinness. 

 At any rate the membrane appeared colorless while the egg con- 

 tents were turned a bright yellow. 



Lillie'-^ has recenth' expressed the opinion that the fertilization 

 membrane is "a paptogen membrane consisting mainly ot protein 

 material." Such a membrane would be much more delicate and 

 easiU ruptured than the fertilization membrane is. Besides 

 there appears to be little if any protein in it as shown by its insolu- 

 bility in pepsin HCl, caustic alkalies and concentrated H.,S04. 

 It ma\' be compared to the cellulose la\ers formed about plant cells 

 after division, or to the chitinous skeleton formed in insects by 

 the hvpodermal cells. In composition it is probably one of the 

 albuminoids. 



' ■ Lillic, I^.: Biol. Bull., xvii, pp. 202, 1909. 



