ANCIENT LIFE ON THE EAETH 37 



SUMMARY 



We have thus arrived at the conclusion that the 

 ocean was the mother of life ; that on its surface 

 floated the first organisms, whose descendants, but 

 little changed during all the millions of years that 

 have since passed away, still float and multiply. Pre- 

 sently some of these animals found their way down 

 to the bottom, where all the debris from the floating 

 organisms collected; and here, in still water, they 

 lived and increased for a long time. Slowly they 

 invaded the rough waters of the coast-line, and, at 

 last, gained a footing on the land. 



It was plants which formed the army of invasion 

 that conquered the land. This army was followed 

 by a mob of camp-followers and ragamuffins, in the 

 shape of cockroaches and scorpions, who fed and 

 fattened on the plants ; but who, notwithstanding 

 their boasted superiority, were quite incapable of re- 

 claiming a single acre of desert. The real victory 

 belongs to the plants, who, with undaunted courage, 

 left the congenial water to dare the vicissitudes of 

 temperature and moisture on land, and thus made 

 civilisation possible. 



Plants left the ocean to live on land once only, in 

 the Cambrian or early Ordovician. Several times, 

 in later days, land plants both Cryptogams and 

 Angiosperms went back to the water; but never 

 again did water plants succeed in gaining the land. 

 And, even at the present day, every seed-bearing 

 plant passes, in its development, through a spore- 



