366 THE ORIGIN OF THE OLDEST FOSSILS. 



piut of -water, one can form some faint conception of tlieir nniversal 

 abundance. 



The organisms which are visible in the water of the ocean and on 

 the sea bottom are almost universally engaged in devouring each other, 

 and many of them, like the bluetish, are never satisfied with slaughter, 

 but kill for mere si)ort. 



Insatiable rapacity nuist end in extermination unless there is some 

 unfailing- supply, and as we lind no visible supply in the water of the 

 ocean we must seek it with a microscope, which shows us a wonderful 

 fauna made up of innumerable larvic and embryos and small animals, 

 but these things can not be the food supply of the ocean, for no carniv- 

 orous animal could subsist very long by devouring its own chddrcn. 

 The total amount of these animals is inconsiderable, however, when 

 comi)ared with the abundance of a few forms of i)rotozoa and proto- 

 phytes, and both observation and deduction teach that the most 

 important element in marine life consists of .some half dozen types of 

 protozoa and unicellular plants; of globigerina and radiolarians, and 

 of trichodesmium, i)yr()cystis, protococcus and the coccospheres rhab- 

 dospheres and diatoms. 



Modern microscopic research has shown that these simple i)lants, 

 and the globigerinic and radolarians which feed upon them, are so 

 abundant and prolific that they meet all demands and supjily the food 

 for all the auinuils 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 sim})licity and abundance of the microscopic 

 forms and their importance in the economy of nature show^ that the 

 organic world has gradually taken sliape around them as its center or 

 starting- point, and has been controlled by them. They are not only 

 the fundamental food supi)ly, but the i)rimeval supply, which has deter- 

 mined the whole course of the evolution of marine life. 



The i)elag-ic plant life of the ocean has retained its i)rimitive simplic- 

 ity 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 hardshi}!. 



On laud the mineral elements of plant food are slowly supplied, as 

 the rains dissolve them; limited space brings crowding and competi- 

 tion 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 the great size and comj^licated 

 structure of terrestrial plants are adaptations to these conditions of 

 hardship. 



At the surface of the ocean the abundance and uniform distribution 

 of mineral food in solution; the area which is available for plants; the 

 volume of sunlight and the uniformity of the temperature are all favor- 

 able to the growth of plants, and as each plant is bathed on all sides 



