i 3 4 SCIENCE PROGRESS 



organisms. In other words we have no reason whatever for 

 supposing that the chlorophyllian plants are anywhere near the 

 bottom of the life scale. 1 



The most reasonable supposition that we can make is that 

 the liberation of oxygen in great quantities by plants began long 

 after a teeming life filled the seas and had at least begun the con- 

 quest {i.e. occupation) of the soil. We have no reason, however, 

 to suppose that the great bulk of the oxygen of the atmosphere 

 was due to land plants. On the contrary, we have the clearest 

 evidence, from the characteristic " colour zones," 2 that climatic 

 conditions were not essentially different far back in the begin- 

 nings of the Cambrian and probably antecedent to the Algonkian. 

 It is possible that the chief producers of atmospheric oxygen 

 were the green algae of the sea and they may be still. Phipson 3 

 reports that the green algae produce, weight for weight, fifty times 

 the quantity of oxygen liberated from a common phanerogam, 

 Polygonum. 



To sum up : from every consideration affording a clue to the 

 conditions under which life might have arisen naturally on the 

 earth ; from the study of the comparative biology of plant and 

 animal and the protista as well as the embryological, develop- 

 mental, physiological and bio-chemical processes ; finally from 

 such geological evidence as we possess, the one conclusion 

 emerges: that the beginnings of life did not involve the inter- 

 vention of uncombined oxygen. 



The gain from this new point of view may not be great but 

 it enables us to delimit the problem one step further, so that we 

 may now say, in the light of our present knowledge : that since 

 anaerobiosis and the fermentative processes are identical, the 

 problem of the genesis of terrestrial life has become that of the 

 natural origin of the organic fermentative substances or enzymes, 

 whose simple collocation into plastids, protomeres, biophores or 

 granules constitutes the primary living units. The aggregation 

 of these latter in turn constitutes the " cell." 



1 For an interesting discussion of this point, cf. M. Kuckuck, Problem d. 

 Urzeugung. p. 60 ff. (Leipzig, 1907). 

 * Walther, I.e. p. 198. 

 3 Chem. News, vols. 67 and 68, 1893. 



