THE pH OF THE BLASTOOELE OF ECHINODERM 



EMBRYOS. 



ROBERT CHAMBERS AND HERBERT POLLACK, 



MARINE BIOLOGICAL LABORATORY, ELI LILLY RESEARCH DIVISION, 



WOODS HOLE, MASS. 



The development of the calcareous skeleton in Echinoderm 

 embryos has been correlated recently with changes in the 

 hydrogen ion concentration (i, 2, 3). This work was based on 

 the results of Rapkine and Prenant (i) who injected indicator 

 dyes into the blastoccele at the various stages of the developing 

 embryo. They found that the pH of the blastocoelic fluid is 7.3 

 in the blastula, 8.5 in the early gastrula when the mesenchyme 

 and the calcareous spicules appear, and 7.3 in the pluteus. 



More recently (4, 5) it has been definitely shown that an 

 evolution of acid occurs when protoplasm is punctured or torn. 

 In view of this, the experiments for determining colorimetrically 

 the pH of the blastoccelic fluid were repeated on Echinoderm 

 larvae obtainable at Woods Hole. 1 



The indicator dyes used were those of Clark and Lubs (6) 

 and ortho cresol phthalein. They were prepared with NaOH 

 in .4 per cent, aqueous solutions. All the solutions except 

 that of brom thymol blue when injected proved to be quite 

 innocuous to the embryos. 



These dyes in sea water, obtained from the laboratory tank, 

 give a color which indicates a pH of approximately 8.4 uncor- 

 rected for salt error and for the possible loss of CO 2 in the 

 hanging drops in which the determinations were made. 



I. INJECTION EXPERIMENTS. 



Asterias. The early blastomeres of the Asterias egg are so 

 weakly adherent that they would fall apart except for the 



1 We wish to take this oppoitunity of expressing our appreciation to Dr. Isabella 

 Gordon of the Imperial College of Science, London, for supplying us with late 

 stages of Echinarachnius and Arbacia larvae from cultures which she was growing 

 at Woods Hole during this past summer. 



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