190 The Mechanistic Conception of Life 



show that it is readily permeable for salts. As long as the 

 cortical layer of the unfertilized egg is intact, it prevents the 

 surrounding salt solution from coming in contact with the proto- 

 plasm or at least it retards this process. If, however, the 

 cortical layer is destroyed by fertilization the surrounding 

 salt solution comes directly in contact with the protoplasm and 

 if the solution is abnormal it can cause the disintegration of the 

 surface layer of the protoplasm. 



I am inclined to believe that differences in the resisting 

 power of various cells or organisms to abnormal salt solutions are 

 primarily due to differences in the constitution of the protective 

 envelopes of the animals or the cells. Microorganisms which 

 can live in strong organic acids or salt solutions of a high 

 concentration probably possess a surface layer which shuts off 

 their protoplasm from contact with the solution. For the 

 protoplasm of muscle the rather tough sarcolemma forms not 

 an absolute but nevertheless an effective wall against the 

 surrounding solution. 



But aside from differences of this kind there are other condi- 

 tions which influence the degree of resistance of cells to various 

 solutions. I have foimd that the fertilized eggs of the sea- 

 urchin will live longer in abnormal salt solutions if the oxida- 

 tions in the egg are stopped, either by the withdrawal of oxygen 

 or the addition of KCN or NaCN. Warburg and Meyerhof 

 have dra^\Tl the conclusion that in a pure NaCl solution the 

 rate of oxidations of the egg of Strongylocentfotus is increased 

 and that it is this increase in the rate of oxidations which kills 

 the eggs. But this increase of oxidations cannot be observed 

 in the eggs of Arbacia when they are put into a pure NaCl solu- 

 tion and, moreover, lack of oxygen prolongs the life of the 

 fertilized egg just as well in solutions of NaCl-f-CaClg or of 

 NaCl+BaCl,, for which salts these authors do not claim that 

 they can raise the rate of oxidations of the egg. I am inclined 

 to believe that during or previously to cell-division, besides 



