62 THE LESSON OF EVOLUTION 



thrown up by the waves ; but they would be rarely 

 seen ; and the great ocean, although really swarming 

 with minute life, would to the naked eye appear 

 tenantless. 



Did Plants Precede Animals ? It is generally sup- 

 posed that plants must have preceded animals ; for 

 they alone are able to decompose the carbon-dioxide 

 in the atmosphere, and thus furnish the carbo-hydrates 

 and proteids on which animals feed. Or, in other 

 words, plants must have preceded animals because 

 they alone can live on mineral substances. But this 

 supposition lands us in the difficulty of having to 

 assume that the very first organism contained chloro- 

 phyll, which is necessary for the formation of proto- 

 plasm, but which is itself a product of protoplasm. 

 This difficulty would be overcome if we could suppose 

 that the primeval ocean, in which the first organisms 

 appeared, contained, in addition to its present salts, 

 mineral hydro-carbons which would slowly oxidise 

 and supply the organisms with food, without the 

 necessity of decomposing carbon-dioxide. Now Pro- 

 fessor H. Moissan has shown that much, if not all, of 

 the carbon of the earth existed at first as metallic 

 carbides, many of which are decomposed by water at 

 ordinary temperatures, and yield hydro-carbons and 

 hydrogen. Most of the hydro-carbons thus obtained 

 are gaseous (acetylene and marsh-gas) ; but in some 

 cases both liquid and solid hydro-carbons are formed 

 abundantly. 1 The gases would be partly taken up by 

 the water, while the liquid and solid forms would 

 float on the surface, and, if converted into carbo- 

 hydrates, may have served as food for the first 



1 Proceedings of the Royal Society of London, vol. Ix. p. 156. 



