THE ORIGIN OF THE OLDEST FOSSILS, ETC. 465 



water of the ocean we must seek it with a microscope, which 

 shows us a wonderful fauna made up of innumerable larvae and 

 embryos and small animals, but these things cannot be the food- 

 supply of the ocean, for no carnivorous animal could subsist very 

 long by devouring its own children. The total amount of these 

 animals is inconsiderable, however, when compared with the 

 abundance of a few forms of protozoa and protophytes, and both 

 observation and deduction teach that the most important ele- 

 ment in marine life consists of some half-dozen types of protozoa 

 and unicellular plants : of globigerina and radiolarians, and of 

 trichodesmium, pyrocystis, protococcus and the coccospheres 

 rhabdospheres and diatoms. 



Modern microscopic research has shown that these simple 

 plants, and the globigerinse and radiolarians which feed upon 

 them, are so abundant and prolific that they meet all demands 

 and supply the food for all the animals of the ocean. 



This is the fundamental conception of marine biology. The 

 basis of all the life in the modern ocean is found in the micro- 

 organisms of the surface. 



This is not all. The simplicity and abundance of the micro- 

 scopic forms and their importance in the economy of nature show 

 that the organic world has gradually taken shape around them 

 as its centre or starting-point, and has been controlled by 

 them. 



They are not only the fundamental food-supply but the 

 primeval supply, which has determined the whole course of the 

 evolution of marine life. 



The pelagic plant-life of the ocean has retained its primitive 

 simplicity on account of the very favorable character of its 

 environment, and the higher rank of the littoral vegetation and 

 that of the land is the result of hardship. 



On land the mineral elements of plant-food are slowly sup- 

 plied, as the rains dissolve them ; limited space brings crowding 

 and competition for this scanty supply ; growth is arrested for 

 a great part of each year by drought or cold ; the diversity of 

 the earth's surface demands diversity of structure and habit, and 



