850 GENERAL METABOLISM [pt. iii 



temperature of — 60° at which to crush the eggs, and got the 

 same results as before, but this improvement does not make the 

 "puree" method inherently more satisfactory. He calculated the 

 intracellular />H of Strongylocentrotus lividus eggs to be 5*8-5-9, and of 

 Arbacia equituberculata 5-0-5-2. But as Chambers & Pollack afterwards 

 pointed out, the worst feature of this method is that the potentiometer 

 gives a curve as the "puree" melts, and the exact point which is 

 chosen for the reading rests on arguments no better than could be 

 adduced for taking it at another point. 



The other type of electrometric method, where electrodes are 

 actually inserted into the tgg, has not been so much used. Bodine, 

 using a micro-electrode of his own design, requiring o-oi c.c. of 

 material, measured the/>H of the egg-contents of Fundulus heteroclitus. 

 The resulting mean average pH was 6-39, and the limits were 6-i 

 and 6-8. No change was to be found at fertilisation or afterwards 

 up to 17 days' development, except that the results after fertilisation 

 seemed to come more constant than those before. Death brought 

 about a very acid reaction, which lowered the j&H as far as 4-4. 

 Placed in hydrochloric acid solutions of pH 4-3, the egg-contents 

 remained quite unaffected for at least 100 minutes, but eventually 

 changes took place inside the egg. As far as this went, the unfertilised 

 eggs were less resistant than the fertilised ones, but there was no 

 change in the relative resistance during subsequent development. 

 Work on Fundulus was continued by Armstrong (but by micro- 

 injection of indicators). The subchorionic space was />H 8-4 ( = sea 

 water) and if the eggs were put into distilled water, descended to 

 5-6 in 18 hours. The pericardial cavity was still 8-4 after that time, 

 however, as were the brain vesicles. The pH. of the yolk was always 

 close to 6-0. 



Bodine's work was hardly a measurement of protoplasmic />H, 

 in view of the highly lecithic nature of the egg of the minnow, but a 

 number of interesting results on frog eggs were supplied by the work 

 of Buytendijk & Woerdemann. They found that the hydrogen elec- 

 trode and the quinhydrone electrode were for various reasons in- 

 applicable to the determination of the intracellular j&H, so they 

 made use of an antimony electrode designed specially for the pur- 

 pose. The micro-electrodes of Ettisch & Peterfi and of Taylor & 

 Gelfan had not been suitable for /)H determinations, but they were 

 modified to carry Buytendijk's antimony electrode. This metal, en- 



