II CLEAVAGE 41 



be brought about suggests that the mechanism of the process 

 is not to be understood by reference to the factors involved 

 in one method alone, the theories which his own experi- 

 ments have induced Loeb to adopt, are well worth a brief 

 discussion. 



As Loeb points out, the whole action falls into two phases. 

 In the first the egg is subjected to the influence of a sub- 

 stance which not only determines the formation of the mem- 

 brane but also sets in motion certain changes which ultimately 

 lead to the destruction of the egg by cytolysis. In the second 

 phase it is rescued from the disastrous effects of the first 

 solution by being immersed in a second. 



It appears that the chain of events set in motion by the 

 first solution (the butyric or other fatty acid) consists in part 

 at least of the oxidation of substances in the egg. The 

 membrane is also formed, but the mechanism of that is 

 another process, to which we shall return in a moment. 



It is known (Warburg) that the unfertilized egg undergoes 

 a very slow oxidation, which is increased many times not 

 only by normal fertilization, but also by the use of the 

 membrane-producing reagent. It is these oxidations that 

 lead to cytolysis, since by them are formed certain decomposi- 

 tion products which are toxic to the egg. 



The function of the second reagent is either to stop this 

 harmful oxidation or else to counteract it. The first is ac- 

 complished by the use of potassium cyanide, which inhibits 

 oxidation generally, and the part played by this substance 

 in the rescue of the egg from death is not hard to understand. 

 But it is more difficult to form a conception of the role of 

 the alternative agent, namely a hypertonic solution, for, as 

 pointed out already, this must be alkaline but must also contain 

 oxygen. If potassium cyanide be added to the hypertonic 

 sea-water, or if the oxygen be removed and replaced by 

 hydrogen, then the solution becomes ineffective or at least 

 requires a much longer sojourn of the eggs in it before they 

 can be made to develop on being replaced in sea-water. 



Hence the evil effects that follow on the oxidations incited 

 by the first solution are counteracted by another oxidizing 



