26 THE LESSON OF EVOLUTION 



necessitate motion in a forward direction only. 



There is no evidence of the existence of any 

 animals sufficiently protected to live among the 

 breakers round the shore , nor is there any evidence 

 of life on land. If a human spectator could have 

 stood on the shore at that time he would probably 

 have seen no animal life at all. The rocks below 

 low-water mark would be covered with delicate red 

 and brown seaweeds, and the ocean between tide- 

 marks would, then as now, be girdled with a belt of 

 vivid green ; but all the land above would be brown 

 and barren, without even a moss or lichen growing 

 on it. Upon the sands at his feet might lie a dead 

 jelly-fish or Trilobite, or, perhaps, a delicate trans- 

 parent shell throw r n 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 1 It is generally 

 supposed 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 chlorophyll, which is necessary 

 for the formation of protoplasm, 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, con- 



