Think of continuous piles of these shells, many hundreds of feet in thickness, all built out of the dead shells of dying millions of tiny creatures. Deep, deep below the surface, where waves had no power, where currents were sluggish, fell a ceaseless gentle rain of these minute shells. Life had fled from each jelly inhabitant; its brief day was over; and the empty shell went quietly down, whether from near the surface or from lower depths, till it reached the ocean-bed. There it lay, forming part of a gathering sticky ooze or mud, which in later times should be slowly hardened into chalk.
But the greater wonder has yet to be told about these shells—these tiny highly-finished constructions.
Not only did a speck of living jelly once inhabit each shell. That speck of living jelly actually MADE the shell.
Not deliberately. Not with intention. Not even consciously. The “making” is in no sense to be confounded with voluntary effort, with the labour which means exertion and fatigue. It was as instinctive, as involuntary, as the “making” of bones in your body and mine.
“But we do not make our bones,” somebody may protest, with a touch of indignation.
Undoubtedly, in a sense, we do. The jelly-speck does not more surely “secrete” its shell, than a man “secretes” his skeleton. Personal will has not to do with the task in either case, beyond the taking in of necessary food; and neither man nor jelly-speck may claim any credit on the score of the pattern worked out.
We have all seen a garden-snail, carrying lightly upon its back its shell or “house,” or outside skeleton. That shell is formed of carbonate-of-lime. In the snail’s slimy body exists a small manufactory for producing or “secreting” carbonate-of-lime. The materials are obtained by the snail through its food. The deposits of it—made as the snail’s nature, certainly not the snail’s reason—dictates, grow into a sheltering framework for its protection.
In a Dictionary we may find the strict meaning of this word “secrete.” It is given as—“to hide; to conceal; to deposit in some secret or private place; to separate from the blood in animals, or from the sap in vegetables, and elaborate into a new product.”
One cannot deny that the word, though used for all such “elaborations,” is more appropriate in the case of a man’s hidden and private framework of bones, than in a snail’s or jelly-creature’s outside shell.
That which the garden-snail so deftly does, is done also by countless billions of minute jelly-specks in the ocean; though with the latter the mechanism is far simpler, because the animal belongs to a far lower and more primitive type.