FORAMINATED SHELLS.

203

CHAPTER IX.

FORAMINATED SHELLS.

I BELIEVE that every one is surprised and delighted with these lovely little shells; so minute that they resemble grains of the finest sand; and so perfect in structure that they seem to be the habitation of a more highly organized animal than they really are.

There are two kinds of foraminated shells, calcareous and siliceous. The calcareous shells are found alive in marine deposit, and on sea-weed; the siliceous are also dredged up from the depths of the sea, and found in strata formed of fossil deposits.

The animals which dwell in these beautiful little shells are of the lowest order in the scale of animal creation, not yet perfectly understood, and are variously placed by scientific men. Formerly they were considered as belonging to the family of Cephalopods, or Cuttle-fish. Ehrenberg, a great naturalist, regarded them as polypes, and placed them amongst the Bryozoa, or Zoophytes. Du Jardin, a French naturalist, and most modern authors, agree in the relationship of foraminifera to those very curious animals, Amaba and Actinophrys sol, which are found in fresh water, and may be studied from our aquariums.

Their internal organization is a simple body of what is called sarcode, a kind of pulp which has the power of assimilating and digesting food in all its parts. The body has no particular mouth, stomach, or intestine, neither has it eyes or other senses, except feeling; but it can put forth long feelers through the perforations in the shell, and can entangle and draw in its appointed food, which, whenever it enters, is presently digested, and the residue ejected, not always out of the shell, for the cavities are sometimes choked up by these undigested atoms.

Now in some of the Foraminifera the body is single and

jointed, in others the chambers of the cells are so distinct that the sarcode body may be considered as compound, and one tiny shell to contain a family, the members of which have been produced as gemmæ or buds, one from the other. The subject is still under investigation by scientific men, therefore I shall not enter further into it, but recommend the student, if desirous of further information, to read "Weaver's Abstract of Foraminifera' in Annals of Nat. Hist., 1841;' Williamson Trans. Micros. Soc., vol. ii,' and Micr. Journal, vol. i;' also 'Carpenter on the Microscope, chap. x.'

The structure of the shell itself is various, some being single-chambered (Lagena, Miliolina, and Gromia); the greater number are compound shells, with cells arranged lengthwise, or circular, or spiral, all of them dotted with numerous foramina, or holes, from whence they are named foraminated shells.

:

We should have at least three slides of these in our collection one of the mixed specimens, one of the beautiful Cristellaria, or Operculina, and one of the siliceous Foraminifera from the Barbadoes deposit.

THE OPERCULINA

is the best example of a compound shell, to show the division into chambers; it is like a tiny nautilus, and if we saw the interior, we should find each chamber separated from the other by double walls, or septa, containing tubes, and which give off lateral branches, and a network of minute veins for circulation of fluid. A large syphon or tube forms the margin of the shell, and is the medium of communication between the cells.

The shells of this Foraminifer being calcareous, are easily dissolved by muriatic acid; and a recent specimen may be examined by placing it in a watchglassful of water with one drop of strong acid, when, in a very short time, the shell will dissolve, leaving the animal naked and perfect with every mark of its habitation left upon its plastic body.

On examining a mixed slide you will find that some are starlike (Astoma), some in complex whorls (Cassidulina),

FOSSIL FORAMINATED SHELLS FROM BARBADOES. 205

some straight and yet chambered (Verneucilina)—the variety is immense. They are dredged from the depths of the Mediterranean, the Adriatic, and Egean Seas, and on our own coast they are found also plentifully in the white drifted sand, or amongst the corallines in rock-pools. The Cassidulina and Rosalina are the most common in the Channel Islands. The ouze of osyter beds also abound with some species.

FOSSIL FORAMINATED SHELLS FROM BARBADOES.

These are of a different kind; the shells are siliceous; the variety even on this one slide is probably amazing, and the delicacy of form and workmanship truly worth a long and careful examination. They were first discovered by Professor Ehrenberg at Cuxhaven on the North Sea, afterwards found by him in collections made in the Antarctic Seas. Fancy these fragile and lovely little creatures having been brought up by the sounding lead at the depth of 2000 fathoms! Such are the beautiful forms which the hand of God has fashioned in His wisdom, where human eye never sees and foot of man never treads, and which, but for our microscope, had remained unknown to us as they have been for the ages past.

Nothing do we examine thus but it reveals such perfect finish, such loving design of adaptation to the creature's necessities, that we have deeper thoughts than our tongue can utter, and learn lessons that philosophy has never taught. Nothing is done carelessly; nothing is isolated or loose in the scale of creation; the plan is seen ever wider, deeper, higher, but complete and in perfect order, whatever part is presented to our finite mind. We see very little, we know very little; but we gaze on, and our hearts are directed upward even by a slide of microscopic shells sculptured with hieroglyphics of the Creator.

The Barbadoes deposit alone furnishes 282 varieties; and when we consider that in a single ounce of sand 6000 of these shells were picked out, and in another ounce from the shores of the Antilles no less than 3,840,000 were discovered; when we learn that these little shells are increasing

so fast as to block up navigable channels, obstruct gulfs, and fill up harbours, we feel how little we can know of that Infinite Mind who has so ordered the multiplicity, and so elaborately worked these foraminated shells.

ORBITOLITES

are circular fossil shells, varying in size from a sixpence to very minute species, found in all foraminiferous sand. It is the habitation of a composite animal, often found alive on sea-weed, but more abundant in the fossil state. The chambers or cells are arranged in circles-the shell not sculptured. The animal is of a less high order than the true Foraminifera. Perforations in the shell are doubtless for the Pseudopodia; their habits and mode of propagation are not known.

NUMMULITES.

These are a species of Foraminifera, but only in the fossil state; they are much larger, too, varying in size from a fourpenny piece to half-a-crown; they are the habitations of a composite animal, and the structure of the shell is very complicate; the chambers are arranged in spirals round the centre in great numbers. They abound in the United States, where a mountain 300 feet high seems to be entirely formed of these shells. The crystalline marble of the Pyrenees and the limestone ranges of the Adriatic Sea are wholly composed of small Nummulites. The Great Pyramid of Egypt is built upon blocks of limestone consisting of these foraminated shells-habitations of beings who lived long before the age of man, and were, amongst others, God's instruments for preparing the earth for the perfection of his

creation.

SPICULES OF SPONGE.

207

CHAPTER X.

SPICULES OF SPONGES.

SPICULES OF SPONGE.

THESE slides, although useful, and to a certain extent interesting, are very far from what is wanted to illustrate the nature of a sponge. They are isolated siliceous spicula of the horny skeleton of the sponge; very various in form, but all for the same purpose of strengthening the framework of the animal.

Sponges in their living state are by no means like the dried specimens sold for domestic purposes; these are but the dead form, the mere skeleton of what was once a living ereature. When alive it possesses a firm, fleshy substance, composed of cells about the 7 of an inch in diameter the horny skeleton is developed in the inter-cellular substance, and within cells of horny matter these spicula are secreted.

;

Sponges present a great variety in their external appearance; some being soft as jelly, whilst others are as hard as flint; some very large, and others exceedingly minute. The nature of the body closely resembles that of the Foraminifera and Amabæ, having no distinct organs, and capable of assimilating food in all its parts. There is a current flowing in and out through the whole sponge, entering the small apertures or oscula, and being expelled by the animal through the large apertures or oscula. The channels through which the currents are drawn and expelled are furnished with ciliated cells, which promote the circulation of the water from whence the sponge derives its needful supply of oxygen and food for the maintenance of its life.

This action may be observed by the sea-side student