ACTION OF THE HYPERTONIC SOLUTION 101 
solution of 50 c.c. of sea-water+4 c.c. of 25 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.' 
1In 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 fir Arzte indicated the importance of the 
