LIFE IN THE OCEAN CLABK 375 



with a reproductive capacity of roughly 1,000,000,000 per month, 

 all of the diatoms could be destroyed except for a single one to each 

 166 quarts of water, yet in a month the full number would be again 

 restored. This shows clearly the immense advantage the minute 

 diatoms have over larger plants as floating organisms in the sea, 

 and why it is that the marine vegetation, except along the shores, 

 is all microscopic, and not only microscopic but extremely small. 



The peridineans, coccolithophorids, flagellates, etc., while very 

 different from the diatoms in bodily form and structure, are more or 

 less similar to them in their relations to the marine world, so that it 

 will not be necessary to consider them in detail. 



While these little plants are able to increase at a most amazing 

 speed and at times occur in incredible abundance, this only takes 

 place under a small range of conditions, occurring for the most part 

 at certain limited seasons. On land in many regions when the 

 drought is broken by the rains, grasses and many other plants im- 

 mediately appear in great abundance. Each grass blade is the equiv- 

 alent in dry nutritive material of many million diatoms, and the 

 synthesis or formation of nutritive material under these conditions 

 is probably at least as rapid as it ever is at sea. 



We live on land and are accustomed to strike an annual average 

 of the conditions on our farms. The study of the sea is in its in- 

 fancy, and we know it mostly from investigations in the spring 

 and summer months. Until we know our seas throughout the year 

 in detail we can not compare its potential productivity with that 

 of our land areas. 



THE INTERMEDIATE FOODS OF THE SEA 



These floating, very small, sea plants occur in all localities, but 

 they are naturally much more abundant in some places than in 

 others. They are subject to great seasonal fluctuations in their num- 

 bers, and they become less common, many of them entirely disap- 

 pearing, toward midocean. 



They are so very small that, although their presence may con- 

 vert the sea water into a thin living-vegetable soup, special adapta- 

 tions are necessary to enable animals to feed upon them. 



These adaptations are along three main lines. 



Many animals of a structure very similar to that of these plants, 

 some almost as small but others larger, live among them, entangling 

 them in networks of slender sticky threads projected from their 

 bodies. Such are the oceanic foraminifera and the radiolarians. 

 Some of the peridineans, too, are incapable of synthesizing inor- 

 ganic into organic substances, and therefore live upon the other 

 little floating plants in the same way that rusts and blights live 

 upon the leaves of plants on land. * 



