Foraminifer

“ These, the films of sarcode probably entangle, surround, and drag into the chambers of the shell, digesting their softer parts in temporary vacuoles, and then casting out the more solid remains just as the Amœba does.” By means of these “pseudopodia” the animal also drags itself along over a fixed surface. Such is the Foraminifer of our own seas, and such too the atomies of the Atlantic basin. ”

“ The manner in which such accumulation takes place we learn from what is now going on in the ocean, more especially from the result of the recent deep-sea dredging expeditions. The Foraminifera are vastly numerous, both near the surface and at the bottom of the sea, and multiply rapidly; and as successive generations die, their shells accumulate on the ocean bed, or are swept by currents into banks, and thus in process of time constitute thick beds of white chalky material, which may eventually be hardened into limestone. ”

“ Whatever may be the mode of life of the Foraminifera, to which the calcareous element of the deep-sea "chalk" owes its existence, the fact that it is the chief and most widely-spread material of the sea-bottom in the intermediate zone, throughout both the Atlantic and Pacific Oceans, and the Indian Ocean, at depths from a few hundred to over 2,000 fathoms, is established. But it is not the only extensive deposit which is now taking place. ”

“ So in the case of a large Sponge or Foraminifer, there may be some special sensation in individual cells, pseudopods, or segments, and the general sensation may be very limited, while unconscious living powers pervade the whole. In this matter of aggregation of animals we have thus various grades. The Foraminifers and Sponges present us with the simplest of all, and that which most resembles the aggregation of « 214 » buds in the plant. ”

“ In like manner, when we meet with a limestone rock entirely composed of the calcareous shells of Foraminifera—some of them entire, others broken up into minute particles—we interpret the phenomenon by the fact that the dredgings obtained from certain parts of the ocean-bottom, consist almost entirely of remains of existing Foraminifera, in which entire shells—the animals of which may be yet alive—are mingled with the debris of others that have been reduced by the action of the waves to a fragmentary state. ”

“ Their shell is either thin or extended many times by long slender tapering spines, and the protoplasm outside has the same character as that of the Radiolaria (q.v.) , being differentiated into jelly containing enormous vacuoles and traversed by reticulate strands of granular protoplasm. These coalesce into a peripheral zone from which protrude the pseudopods, here rather radiate than reticulate. Most genera and most species are cosmopolitan; but local differences are often marked. Foraminifera abound in the shore sands and the crevices of coral reefs. ”

“ Thus the majority are littoral or deep-sea, sometimes attached to other bodies or even burrowing in the tests of other Foraminifera; most of the fresh-water forms are sapropelic, inhabiting the layer of organic débris at the surface of the bottom mud ditches of pools, ponds and lakes. The deep-sea species below a certain depth cannot possess a calcareous shell, for this would be dissolved ”

“ What we see in a many chambered foraminifer, such as Globigerina or Rotalia, is just the same thing, save that it is carried out in greater completeness and perfection. The little organism as a whole is not a figure of equi­lib­rium or of minimal area; but each new bud or separate chamber is such a figure, conditioned by the forces of surface tension, and superposed upon the complex aggregate of similar bubbles after these latter have become consolidated one by one into a rigid system. ”

“ The general character of the rock connected with the fossil produces the impression that it is a great Foraminiferal reef, in which the pyroxenic masses represent a more ancient portion, which having died, and having become much broken up and worn into cavities and deep recesses, afforded a seat for a new growth of Foraminifera, represented by the calcareo-serpentinous part. ”

“ Nummulites are large cone-shaped foraminifera with many chambers arranged in spiral order. In Britain the small globular shells of Saccamina are important constituents of some Carboniferous limestones; but the upper portion of that formation in Russia, eastern Asia and North America is characterized by the occurrence of limestones filled with the spindle-shaped shells of Fusulina, a genus of foraminifera now extinct.
Coral limestones are being formed at the present day over a large extent of the tropical seas; many existing coral reefs must be of great thickness. ”

“ It is obvious enough that the spiral shells of the Foraminifera closely resemble true logarithmic spirals. Indeed so precisely do the minute shells of many Foraminifera repeat or simulate the spiral shells of Nautilus and its allies that to the naturalists of the early nineteenth century they were known as the Céphalopodes microscopiques543, until Dujardin shewed that their little bodies comprised no complex anatomy of organs, but consisted merely of that slime-like organic matter which he taught us to call “sarcode,” and which we learned afterwards from Schwann to speak of as “protoplasm.” ”

“ The one force is perpetually undoing what the other force is perpetually doing. Innumerable multitudes of living creatures are at work, taking lime from the water, and constructing carbonate-of-lime. But the ocean is ever seeking to re-dissolve that carbonate-of-lime.
Another difficult question as to the ooze was—whether the shells of which it is mainly made were those of Foraminifera living in the deep sea, far down below the surface, or of Foraminifera living near the surface. ”

“ Dr. Carpenter, in his work on the microscope, says: "Many parts of it (the chalk) consist in a great measure of the minuter parts of the smaller kinds of Foraminifera, whose shells are imbedded in a mass of apparently amorphous particles, many of which nevertheless present indications of being the worn fragments of similar shells, or of larger calcareous organisms. In the chalk of some localities, Foraminifera constitute the principal part of the minute organisms which can be recognised with the microscope ”

“ As I have pointed out elsewhere, [7] it at once became obvious that the calcareous, sticky mud of the Atlantic was made up, in the main, of shells of Globigerina and other Foraminifera, identical with those of which the true chalk is composed, and the identity extended even to the presence of those singular bodies, the coccoliths and, the true nature of which is not yet made out. Here, then, were organisms, as old as the Cretaceous epoch, still alive, and doing their work of rock-making at the bottom of existing seas. ”

“ The PROTOZOA.—The Protozoa are represented throughout the whole range of geological series, from the Lower Silurian formation to the present day. The most ancient forms recently made known by Ehrenberg are exceedingly like those which now exist: no one has ever pretended that the difference between any ancient and any modern Foraminifera is of more than generic value, nor are the oldest Foraminifera either simpler, more embryonic, or less differentiated, than the existing forms. ”

“ The bed of the deep Atlantic is covered, for the most part, by a mud or ooze, largely made up of the débris of foraminifera and other minute organisms mixed with fine clay. In the North Atlantic the Norwegian naturalists call this the Biloculina mud. Farther south, the Challenger naturalists speak of it as Globigerina ooze. In point of fact it contains different species of foraminiferal shells, Globigerina and Orbulina being in some localities dominant, and in others, other species; and these changes are more apparent in the shallower portions of the ocean. ”

“ C. From between Natua and Mbatiri, about 290 feet above the sea. This is a relatively deep-water deposit, the foraminifera being minute and of the “Globigerina” type. About 90 per cent. of the residue consists of fine clayey material, with which the calcite is so intimately mixed that each particle is highly refractive and effervesces freely in an acid. The mineral fragments (pyroxene and felspar) are very scanty, the largest being less than ·25 mm. The white casts of foraminifera, composed of chalcedonic silica, form a conspicuous elements in the residue. ”

“ The marine fauna comprised foraminifera which must have swarmed in the Chalk and some of the limestone seas; their shells have formed great thickness of rock. Common forms are the genera Alveolina, Cristellaria, Rotalia, Textularia, Orbitolina, Globigerina. ”

“ The friable calcareous strata at Grignon are a loose aggregate of the shells of foraminifera and minute mollusks; and as the fossil shells from that locality are very common, and generally filled with debris, the student will have no difficulty in obtaining specimens for examination. The tertiary argillaceous deposits of England are less rich in foraminifera than the arenaceous; but the usual types occur in the London Clay, at Highgate, Clapham Common, Bracklesham Bay, &c. The Eocene marls of the United States are rich in foraminifera. ”

“ In the shallower waters the foraminifera, with their calcareous shells, prevail, but over the deeper abysses of the ocean they take so long in falling that the calcareous shells are dissolved in the water, which contains a considerable proportion of carbonic acid gas, and their place is taken by the siliceous skeletons of the radiolarians and diatoms. Thus there is a ceaseless falling of organisms from above, and it must be from these that the dwellers of the deep ultimately obtain their food. As Mr. Kipling in his ‘Seven Seas,’ says of the deep-sea cables:
‘The wrecks dissolve above us ”

“ Life in the ocean in those old geologic days was a long guerrilla warfare—every animal guarding against attack, and at the same time watching sharply for an opportunity to seize and prey upon some weaker companion. As for the foraminifers and other microscopic creatures, they were countless, and their skeletons, singly invisible, have by accumulation built up great masses of rock, like the chalk-beds of England and France. ”

“ It is remarkable that the humbly organized living things which built up the Laurentian limestones have continued to exist unchanged, save in dimensions, up to modern times; and here and there throughout the geological series we find beds of Foraminiferous limestone, similar, except in the species of Foraminifera composing them, to that of the Laurentian. It is true that other kinds of creatures, the coral animals more particularly, have been introduced, and have proved equally efficient builders of limestones ”

“ It can scarcely, I think, be questioned that such a continuity of the leading types of Foraminifera maintained through so long a series of geological periods, and the recurrence of similar varietal departures from those types, is a result of the facility with which creatures of such low and indefinite organization adapt themselves to a great variety of external conditions; so that, on the one hand, they pass unharmed through changes in those conditions which are fatal to beings of higher structure and more specialized constitution ”

“ A very remarkable point which has led to great confusion in the study of the Foraminifera, is the fact that the shell on which we base our characters of classification, may vary very much, even within the same individual. Thus in the genus Orbitolites the first few chambers of the shell have the character of a Milioline, in Orbiculina of a Peneroplis. ”

“ With the actual origin or mode of development of the foraminiferal shell we are now but little concerned. The main factor is the adsorption, and subsequent precipitation at the surface of the organism, of calcium carbonate,—the shell so formed being interrupted by pores or by some larger interspace or “mouth” (Fig. 308) , which interruptions we may doubtless interpret as being due to unequal distributions of surface energy. In many {589} cases the fluid protoplasm “picks up” sand-grains and other foreign particles, after a fashion which we have already described (p. 463) ”

“ Our own experience of the wide limits within which any specific group of the Foraminifera multiply their varietal forms, related by some peculiar conditions of growth and ornamentation, has led us to concur fully with those who regard nearly every species of Foraminifera as capable of adapting itself, with endless modifications of form and structure, to very different habitats in brackish and in salt water ”

“ The chalk, which alone attains a maximum thickness of 1000 feet, and, according to Lyell, can be traced across Europe for 1100 geographical miles, may be said to be entirely composed of shells of Foraminifera imbedded in a paste of still more minute calcareous bodies, the Coccoliths, which are probably products of marine vegetable life, if not of some animal organism still simpler than the Foraminifera. ”

“ The genus Fusulina (fig. 20) and Saccammina (fig. 19) give their names (from their respective abundance) to two limestones of the Carboniferous series. Porcellanous shells become abundant only from the Lias upwards. The glauconitic grains of the Greensand formations are chiefly foraminiferal casts. Chalk is well known to consist largely of foraminiferal shells, mostly vitreous, like the north Atlantic globigerina ooze. In the Maestricht chalk more littoral conditions prevailed, and we find such large-sized species as Orbitoides (vitreous) and Orbitolites (porcellanous; figs. 5, 6) , &c. ”