Diatom

But diatoms contribute indirectly to the nourishment even of the great North Atlantic whales, for these feed chiefly on the acorn-like medusae brought to them by the Gulf Stream, which sometimes cover the ocean so thickly as to make it look like a prairie strewn with yellow leaves.

Each medusa consists of from five to nine lobes, and as each lobe has been found filled with diatoms to the number of seven hundred thousand, each individual must swallow from three and a half to more than six millions at a meal.

Diatoms have another important function which will be referred to later, but the countless millions which are forever dying and sinking must form a considerable item in the bill of fare of many of the creatures which live at the bottom of the sea and are therefore wholly dependent upon what is brought to them, for there are no beds of weed to which they can go for a meal.

Seaweeds require a certain amount of light and usually form only a fringe about a mile wide round the coast, being practically limited to depths of less than a hundred fathoms, though stragglers are met with here and there.

Footnote.