ACTION OF THE HYPERTONIC SOLUTION 101 



solution of 50 c.c. of sea-water +4 c.c. of 2J m NaCl considerable 

 changes take place in the chemical reactions within the egg. 

 These changes lead to those effects which, after membrane 

 formation, allow the egg to develop normally upon transfer- 

 ence to ordinary sea-water. 



3. The third factor which determines the length of exposure 

 to the hypertonic solution is the temperature. In my first 

 papers upon artificial parthenogenesis I was undecided as to 

 whether the hypertonic solution has a purely physical or a purely 

 chemical action. I had found in 1892 that it prevents cell divi- 

 sion more quickly than nuclear division. Since a hypertonic 

 solution prevents cell division more easily than nuclear division, 

 one can obtain, at a certain minimal grade of the hypertonicity 

 of the solution, nuclear division without cell division. It is 

 quite possible (though not proven) that this prevention of 

 cleavage depends upon the rise in viscosity of the protoplasm, 

 owing to the withdrawal of water from it in the hypertonic solu- 

 tion. On the other hand, it was not very probable that the 

 activation of the unfertilized egg by a hypertonic solution could 

 be referred to a physical effect. 



The determination of the temperature coefficient affords us 

 a ready means of differentiating whether a given physiological 

 process depends upon a chemical reaction or upon a purely 

 physical change. As van't Hoff and Arrhenius have shown, 

 the temperature coefficient for chemical reactions is relatively 

 high, viz., not less than 2 for 10 C., while physical processes 

 possess in general a lower temperature coefficient. We can in 

 this way set up a criterion whether the effect of the hypertonic 

 solution upon the egg after artificial membrane formation 

 depends upon the influence of a chemical reaction within the 

 egg or a physical process. 1 



i In my first researches upon the effects of salts, I was troubled because I 

 possessed no criterion to decide whether I had to deal with purely physical phe- 

 nomena, e.g., coagulations, or with chemical processes. Cohen's admirable 

 Vorlesungen ueber physicalische Chemie fur Arzte indicated the importance of the 



