l62 L. V. HEILBRUNN. 



(or as would no doubt be a more exact expression of fact, the 

 membrane still offers sufficient resistance to the passage of 

 MgClo so that this [salt exerts osmotic pressure against it). 

 Indeed after being collapsed by the MgCl 2 , the previously 

 elevated membrane behaves as a semipermeable membrane 

 and shrinks with the egg. 



That the membrane is still "semipermeable" shortly after 

 elevation is also shown by another series of experiments. It 

 was found that the well-known collapse of the elevated membrane 

 in solutions of egg albumen, did not take place immediately 

 after elevation. 



In an experiment of July i, 1914, eggs were inseminated in a 

 Syracuse dish at 9:43 A.M. Two drops of egg suspension were 

 then placed 'in various Syracuse dishes containing 10 c.c. of 

 i per cent, egg albumen 1 in sea-water, at intervals of 1,3, 6, 

 12^ minutes after insemination. In the case of the eggs placed 

 in the albumen solution i and 3 minutes after insemination, 

 the membrane was well elevated and had suffered no collapse. 

 On the other hand, when the eggs which had been placed in the 

 albumen solution 6 and \2\ minutes after insemination were 

 examined, their membranes were found to have been bent back 

 and collapsed. This experiment was repeated a number of 

 times, similar results being obtained in each case. 



These surprising results find an easy explanation on the 

 ground that the membrane is still partially permeable shortly 

 after elevation. Because of this semipermeability it is subjected 

 to the pressure of the electrolytes contained within it. Only 

 when the membrane loses its semipermeable properties does 

 this pressure cease and only then can the albumen cause its 

 collapse. The albumen seems to exert a protective effect 

 on the membrane and to prevent increase of permeability. Thus, 

 when eggs were placed in albumen i minute after insemination^ 

 their membranes were found to retain their semipermeability 

 and they collapsed upon being placed into 2 M MgClo 14 

 minutes after insemination. 



From these experiments we can, I think, conclude that in- 

 creased permeability follows upon, rather than precedes, mem- 



1 Kahlbaum's crystallized egg albumen was used. The solution was filtered. 



