LIFE IN THE SEA 473 



but highly organized. Such an exception as the Zostera, 

 which really has minute flowers, obviously represents 

 a modified form of inland ancestry. Closer examina- 

 tion shows that the conspicuous seaweeds are confined 

 to the coast belt and certain areas where floating 

 species exist. The greater part of the ocean is without 

 noticeable plant life, though the upper layers are full 

 of minute diatoms and other equally inconspicuous 

 though by no means insignificant types. The sunless 

 depths have no plants at all. Every part of the sea, 

 on the other hand, supports animal life. It abounds in 

 the far north and south, where land life is scarce. It 

 exists in the abyssal depths, which occupy nearly half 

 the earth's surface. It includes great numbers of 

 groups, such as the starfishes, crinoids, and lamp 

 shells, which have no terrestrial or even fresh-water 

 analogues. In the past it was the same. The rocks, 

 dating back millions of years, are full of marine shells, 

 echinoderms, fishes, and the rest, but we rarely find 

 recognizable plants in sea deposits. 



The land, on the other hand, is often covered with 

 forests. The higher plants are all terrestrial. Animal 

 life on land, in spite of its high development, seems 

 almost secondary to the flora. Only in towns do the 

 animals (principally Homo sapiens) appear to exceed 

 the plants. Rocks formed inland often contain plant 

 remains in great variety, without 'a single animal. 



3. Looking out upon the ocean, we get the impres- The littoral 

 sion of extraordinary uniformity. North, south, east, 

 and west, wherever the sea extends, we find a waste 

 of waters, - - without mountains, without valleys, with- 

 out forests or rivers. It is only after close study that 

 we appreciate the erroneousness of this superficial 

 view. There are currents in the sea, flowing like 



zone 



