848 GENERAL METABOLISM [pt. m 



corresponded exactly with the time of skeleton formation, as the 

 other curve on the graph shows, relating as it does number of embryos 

 with spicules to time. More recently, however, the micro-injection 

 work of Rapkine & Prenant has been repeated by Chambers & 



6 Hours 



(Spectral 

 absorption) 



Control 



(sea water 



alone) 



% of the 



gastrulae 



possessing 



spicules 



4.5 



4-0- 



3-5 



3-0 



100 



50 



Fig. 209. 

 Experimental values 



— • — Corrected values 



Pollack, who have not been able to find similar results. Using the 

 blastulae of Asterias forbesii, Echinarachnius parma, and Arbacia punctu- 

 lata, they micro-injected dissolved indicators into the blastocoele 

 cavity, and in all cases found its pH to be the same as that of the 

 external sea water. If the latter was brought down to pYi 5 or 6, the 

 liquid in the blastocoele cavity also gave a result of j&H 5 or 6. 

 Chambers & Pollack claimed that, by using very slender pipettes and 



