Foraminifera

“ 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 ”

“ 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 ”

“ 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. ”

“ 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. ”

“ Thus some of the Foraminifera appear to have survived, with little or no perceptible alteration, from the Silurian period to the present day; whereas large and highly-organised animals, though long-lived as individuals, rarely seem to live long specifically, and have, therefore, usually a restricted vertical range. ”

“ 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 ”

“ 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 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. ”

“ The nucleus is single in the Nuda and Allogromidia and in the megalospheric forms of higher Foraminifera; but microspheric forms when adult contain many simple similar nuclei. The nucleus in every case gives off granules and irregular masses (“chromidia”) of similar reactions, which play an important part in reproduction. During the maturation of the microsphere the nuclei disappear ”

“ We have spoken of foraminifera as floating freely about in the sea water, but while it is certain that many of them live at or near the surface, some are known to thrive at considerable depths; and those who desire to study the various forms of these interesting creatures should search among dredgings whenever an opportunity occurs. ”

“ 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. ”

“ Passing to the typical, calcareous-shelled Foraminifera, we have the most symmetrical of all possible types in the perfect sphere of Orbulina; this is a pelagic organism, whose floating habitat places it in a position of perfect symmetry towards all external forces. Save for one or two other forms which are also spherical, or ap­prox­i­mate­ly so, like Thurammina, the rest of the monothalamic calcareous Foraminifera are all comprised by naturalists within the genus Lagena. ”

“ Now the modifications which any single type of Foraminifera must have undergone, to give origin to the whole series of diversified forms now presented by that group, are not greater in comparison with the modifications of which we have direct evidence, than are those which the advocate for the specific unity of the human races has no hesitation in assuming as the probable account of their present divergence. ”

“ 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 ”

“ A hard dark grey rock containing 10 or 15 per cent. of carbonate of lime and showing fine specks of pyrites. In the slide are displayed numerous tests of foraminifera of varying size up to ·5 mm.; scattered patches of pyrites; fragments of a semi-vitreous basic rock, not exceeding ·15 mm. in diameter, and of plagioclase and pyroxene; in a matrix of the finest debris of the same materials impregnated with granules of calcite. The tests of the foraminifera are filled either with calcite, showing a black cross in polarised light, or with a zeolite, or with pyrites, or with the matrix. ”

“ Those forms which make the deep-sea oozes live, not on the bottom, but near the surface of the open sea, and on the death of the organisms, the shells, tests, and skeletons sink to the bottom. Chalk is formed in a similar way from calcareous Foraminifera, but not necessarily in very deep661 water. Foraminifera live in shallow water as well as in the open sea, and in this case they sometimes creep on the bottom or are attached to algæ, but their deposits in shallow water are usually much obscured by other kinds of deposition and by destructive action. ”

“ 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 bodies of the Foraminifera are formed of a gelatinous substance, sometimes entire and round, sometimes divided into segments, which can be placed upon a line, simple or alternate, wound up into a spiral form or rolled round its axis, like a ball. ”

“ 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. ”

“ With respect to the distribution of the Foraminifera according to [94] geological periods, we may briefly state that they have been found in every formation from the Silurian to the Tertiary. The species, at first very simple in their forms, begin to appear in increasing numbers in the carboniferous formations. They become more numerous, and, at the same time, more complex in their forms, in the Cretaceous period; they are still more diversified, and appear to have multiplied much more [95] rapidly in the Tertiary period, where they attain the maximum of their numerical development. ”

“ 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. ”

“ We have had occasion before to speak of these animals, and as they are not conspicuous or commonly-known forms of life, it may be well to say a few words as to the structure of the living representatives of the group. The Foraminifera are all inhabitants of the sea, and are mostly of small or even microscopic dimensions. ”

“ 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. ”

“ 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. ”

“ The foraminifera exist now, as they existed millions of years ago; but the fact that they co-exist with higher forms of physical life does not show that the higher forms of life are but foraminifera in a more highly evolved form. ”

“ After I had learned a great many interesting things about the life and habits of the children of the sea—how in the midst of dashing waves the little polyps build the beautiful coral isles of the Pacific, and the foraminifera have made the chalk-hills of many a land—my teacher read me "The Chambered Nautilus," and showed me that the shell-building process of the mollusks is symbolical of the development of the mind. ”

“ The mode of filling thus suggested for the chambers and tubes of Eozoon, is precisely that which takes place in modern Foraminifera filled with glauconite, « 178 » and in Palæozoic crinoids and corals filled with other hydrous silicates.
5. The type of growth and structure predicated of Eozoon from the observed appearances, in its great size, its laminated and acervuline forms, and in its canal system and tubulation, are not only in conformity with those of other Foraminifera, but such as might be expected in a very ancient form of that group. ”

“ The objections which not unnaturally occur to those familiar with only the ordinary forms of Foraminifera, as to the admission of Eozoon into the series, do not appear to me of any force. These have reference in the first place to the great size of the organism ”

“ 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. ”

“ Carpenter and Professor Williamson: than whom there are none more competent.
FORAMINIFERA.
The Foraminifera are marine animals of low organization, and, with but few exceptions, extremely minute: in an ounce of sea-sand between three and four millions have been distinctly enumerated. When living, they are not aggregated, but always individually distinct; they are composed of « 340 » a body, or vital mass, of a gelatinous consistence, which is either entire and round, or divided into segments, placed either on a simple or alternate line, or coiled in a spiral, or involuted round an axis. ”

“ It is this composite sort of life which is connected with the main geological function of the Foraminifer. While active sensation, appetite, and enjoyment pervade the pseudopods and external sarcode of the mass, the hard skeleton common to the whole is growing within; and in this way the calcareous matter is gradually removed from the sea-water, and built up in solid reefs, or in piles of loose foraminiferal shells. Thus it is the aggregative or common life, alike in Foraminifers as in Corals, that tends most powerfully to the accumulation of calcareous matter ”