646 



THE RESPIRATION AND 



[PT, III 



where they can be measured best, no rhythmical phenomena occur. 

 The facts are much more in agreement with the view of Warburg, 

 expressed in his review of 19 14, that the respiration of echinoderm 

 eggs is a function of the cytoplasm, and is independent of the synthesis 

 of the nucleus. Matthews' observation that, in the absence of oxygen, 

 the astral rays disappeared, need not mean that they use oxygen, but 

 simply that, in the absence of the fundamental metabohc processes 

 normally going on, the morphological processes are inhibited. This 

 resembles some of the effects we have already noticed in the work 

 of Warburg. 



" be K 

 a> 7 



f-S 6 



bo 



S^S 



3 - 



1^^ 



10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 

 Time in hours after fertilisation 



Fig. 113. 



Shearer followed the oxygen consumption of echinoderm eggs for 

 the first lo minutes after fertihsation. Gray as far as about i6 hours, 

 i.e. as far as the i6-cell stage in certain cases, and Warburg as far 

 as 25 hours, i.e. gastrulation. Rapkine in 1927 followed the process 

 further still. Warburg and Shearer referred their determinations to 

 amounts of nitrogen, but Rapkine improved on this by using dry 

 weight. His estimations were done by the Winkler method. The 

 results were rather perplexing, for, when the mgms. of oxygen con- 

 sumed per I gm. dry weight of eggs were plotted against time (see 

 Fig. 113), a curve was obtained which ascended slowly towards the 

 24th hour, after which it entered on a plateau indicating apparently 

 a uniform metabolic rate as far as the 40th hour. This in itself 

 agrees fairly well with Warburg's curve, except for a slight initial 

 fall about the 3rd hour after fertilisation, for which there is no 



