596 SCIENCE PROGRESS 



is, the rate is approximately doubled with each io° C. increase 

 in temperature. It seems probable from all this that the 

 synthesis would have been rapid, and the capacity of the 

 oceans to sustain life may very quickly have reached the satura- 

 tion point. Estimating this period at not more than a few 

 hundred or a few thousand years, and setting this over against 

 perhaps fifty or a hundred million years which have since 

 elapsed, we shall conclude that the quantity of life on the 

 earth has perhaps been nearly constant throughout the whole 

 range of geological time. There may have been some fluctua- 

 tion through the reduction of the quantity of required in- 

 gredients to below minimal requirements. But from the known 

 action of the sea in regulating the quantity of carbon dioxide 

 in the atmosphere,, variation from this source would scarcely 

 have been great, nor have we much evidence for any great 

 variation in the quantity of phosphoric acid and silica. 



The evidence of wide variation in fossil life is scarcely to 

 the point, since now as always the vast bulk of living substance 

 is non-calcareous. In periods of glaciation, supposing the re- 

 duced temperature world-wide, there may have been consider- 

 able increase to even Arctic abundance. But in general it 

 seems probable that life on the earth has varied rather in the 

 forms of its transient aggregation than in volume. 



New York, Dec. i, 1908. 



