Then a deep-sea dredge, plunged into the ooze, carried away half-a-ton of it, and men began to realise what its presence might mean. By a long succession of soundings, its true nature became slowly manifest.
The ooze was found to be composed chiefly of tiny rounded shells, called “Globigerina,” which belong to a larger class, known as “Foraminifera.” And the white chalk of our British cliffs is made principally of Foraminifera shells.
This last name springs from two Latin words, meaning “I bear a hole.” The Foraminifera shells bear many holes. Each is in shape a tiny collection of rounded compartments, usually not more than sixteen in number; and each compartment has numerous minute holes in its walls.
Its inhabitant, a speck of jelly, is one of the least of living creatures, belonging to the great Division of “Protozoa,” or “First Animals.” None rank below them, for they are on the first or lowest rung in the ladder of life.
A jelly-speck has no head, no limbs, no stomach, not even a mouth. It can take in food at any part of its soft body. When it wishes—and apparently even a jelly-speck can wish, which at once separates it from inanimate materials—it makes a temporary tentacle or “foot,” by pushing out a slender filament of its own substance through one of the tiny holes in its shell. Whence the name “Rhizopod.”
Not all the Foraminifera specks live in the same kind of sheltering skeletons. Some construct delicate domes or many-chambered discs of sand-grains, joined together with enough carbonate-of-lime to act as building-cement. Such skeletons are called “tests,” to distinguish them from “shells” proper.
Hardly anything can be more remarkable than the way in which these tests are put together by mere specks of jelly, alive indeed, but without parts, without development, without understanding. How and why they should choose from one place, each the especial materials which go to form its own kind of “test,” is one of the mysteries in Nature for which Science has no explanation. We can but look and marvel.
One kind of jelly-speck will use the larger grains of quartz, arranging them, and joining them into a bottle-shaped test or shelter.
Another, in the same spot, belonging to a different species, will select tinier grains of the same substance, and will build out of them a rounded sphere, exquisitely modelled, with tiny holes at intervals for the protruding “limbs.”
Another, of yet a different species, picks out the minutest of sand-grains and of bits of sponge-spicules, and knits them together, without any cement, into delicate white globes, “like homœopathic globules,” giving to each a single opening.