SECT. 6] OF THE EMBRYO 851 



closed in a glass micropipette, proved very useful, for, as has long 

 been known, it gives a potential difference depending regularly on 

 the hydrogen ion concentration of the liquid with which it is in 

 contact. Placed in one blastomere of an amphibian egg, the electrode 

 was made to register graphically changes in pH. The eggs used were 

 those of Amblystoma, Triton taeniatus and Rana temporaria. The main 

 results were as follows: 



Ovarial eggs ... ... 7'2 



Fertilised eggs ... ... 8-5 



2 -cell stage 8-5 



4-cell stage ... ... ... 8-05 



32-cell stage ... ... 7-9 



64-cell stage ... ... 7*9 



As regards the intracellular pYi, the value of 7-2 for the ovarial 

 eggs was almost exactly the same as that of the adult blood, i.e. 

 7-35, a fact which recalls the osmotic pressure measurements of 

 Backmann and his collaborators. It was not in agreement, however, 

 with Reiss' value of 6-o for the unfertilised frog's tgg, by the micro- 

 compression method. Newly laid eggs surrounded by solutions of 

 />H 5-9 or 7-7 showed no change at all in intracellular pH, at any 

 rate over a comparatively short period. Buytendijk & Woerdemann 

 inserted their electrode into one blastomere after another in the same 

 embryo without ever finding more than minute differences in p\i. 

 Cytolysis, they found, led invariably to a decrease in p¥L, obviously 

 due to acid production, thus agreeing with our results and those of 

 Chambers & Pollack on echinoderm eggs. The fact that the eggs 

 which had been pierced many times with the antimony electrode still 

 continued to divide normally indicated, they felt, that it was a very 

 harmless instrument. 



They emphasised the fact that the amphibian eggs registered a 

 very marked change in/?H on fertilisation, contrary to what had been 

 found for echinoderm and teleost eggs. Their rise of 1-25 j&H units 

 then was in agreement with Reiss' rise of o-4/>H units. But what was 

 most noticeable about their values was that they were all distinctly 

 higher than those of any other investigators, and while this may 

 be due to the special material they employed, it is also very likely 

 that of all the methods which ha\e been used theirs does least 

 injury to the cell, and so causes least production of acid. It would 

 be extremely interesting to use the antimony micro-electrode on 



