This section is from the book "General Outline Of The Organization Of The Animal Kingdom, And Manual Of Comparative Anatomy", by Thomas Rymer Jones. Also available from Amazon: A General Outline of the Animal Kingdom and Manual of Comparative Anatomy.
(22). In Faujasina and the Nummulites, apparently the most highly organized of the Foraminifera, the shell is of more complicated structure, being permeated by a system of radiating interseptal canals communicating with the exterior.
(23). For the following observations relative to the reproduction of the Foraminifera we are indebted to Professor Max Schulze *.
Remarking that an individual of the genus Triloculina (D'Orbigny) had become stationary for several days, and enveloped, as is not usual, in a thin layer of brownish slime, Professor Max Schulze1 paid particular attention to it. At the end of a few days after it had become quiescent, minute spherical, sharply defined granules were detached from the brownish slimy envelope, and in the course of a few hours the animal was surrounded with about forty of these corpuscles, which gradually became more and more separated from it. Microscopic examination proved that these were young Foraminifera. When viewed by transmitted light, they presented a pale-yellowish-brown calcareous shell, consisting of a central globular portion partly surrounded by a closely-applied tubular part, and having no septum in the interior. In a short time the young animals protruded their contractile processes from the anterior opening of the shell and crawled about upon the glass. The parts of the body contained within the shell could be examined with great accuracy under the highest magnifying powers, and were seen to consist of a transparent, very finely granular, colourless material, of which the protruded filaments were an immediate continuation.
From the circumstances under which the young Foraminifers made their appearance, they must necessarily quit their parent in a tolerably perfect condition.
(24). When the calcareous shell of the parent animal was carefully broken up, it was found to contain only trifling remains of a finely granular organic substance, which, after careful and continued observation, exhibited no trace of motion such as is often, under other circumstances, presented in separated particles of the animal substance, nor could he perceive any vestige of a young one in process of development. The almost complete absence of any organic contents in the shell of an individual which from eight to fourteen days previously was creeping about, renders it probable that the whole (or, at any rate, part) of its body had been transformed into young ones.
* Muller's Archiv, 185G, p. 163.
1 Professor Max Schulze, Ueber den Organismus der Polythalamien (Foraraini-feren.) Leipzig, 1854.
(25). It is astounding to reflect upon the multitudes of these microscopic shells which crowd almost every sea-beach. In some cases at least one-half of the bulk of the sand seems to consist of these elegant organisms. Plancus (Ariminensis, De Conchis minus notis) counted 6000 in a single ounce of sand from the shores of the Adriatic; and D'Orbigny estimated that an ounce of sand procured from the Antilles contained not fewer than 3,800,000! The numbers therefore contained in a square yard are beyond all human calculation; and yet, what is that when compared with the extent of sea-coast in all parts of the globe? Probably therefore no race of animals is more numerically important than that we are now considering. Their remains constitute a great proportion of the so-called sand-banks which often so materially interfere with navigation by obstructing the entrance to bays and straits, or, as is the case with the port of Alexandria, blocking up harbours. They enter largely into the formation of coral islands, and not unfrequently compose extensive geological deposits. One solitary species of the genus Fusulina has, in Russia, given rise to enormous beds of calcareous shells. The cretaceous formations both of France and England contain them in immense quantities.
The tertiary strata abound with numerous species; and the very stones of which the largest of the Pyramids of Egypt is built are principally composed of shells (Nummulites) belonging to this important group. The tertiary basins of the Gironde, of Austria and of Italy, and more especially the "calcaires grossiers" of the vast Parisian basin, are in some parts so filled with them, that 58,000 have been counted in a cubic inch, or about 3,000,000,000 in a cubic yard - figures that may well spare us further calculation. In fact, it might be stated without exaggeration, that the city of Paris, as well as many of the towns and villages in the surrounding departments, are almost entirely built of stones that seem to be mere agglomerations of these microscopic shells.
(26). The substance of the shell in the Foraminifera varies to a certain extent in accordance with its mode of growth. When the calcareous investment is made up of segments involving each other, it is of a dense texture, resembling porcelain. When the segments alternate without a spire, or when the spiral revolution is oblique, the shell is porous, and perforated, more especially in the last-formed compartments, by numerous apertures through which the pseudomelia are protruded. When the segments are all placed in a straight line, or when they are rolled in a spiral upon the same plane, or when they are alternate and the shell is inequilateral, their texture is very generally transparent like glass *.
(27). Nearly related to the Foraminifera, or at least apparently belonging to the same general type of structure, are the Polycystina, an extensive group of very interesting microscopic bodies possessing great beauty and variety of form and structure. These are minute silicious shells, which appear, from the recent observations of Professor Miiller 1, to contain in the living state an olive-brown sarcode extending itself into pseudopodial prolongations that pass through the large apertures by which the shells are perforated. The sarcode does not seem always to fill the shell, but only its upper part or vault, and to be very regularly divided into four lobes. It is a peculiar feature in these Polycystina that their shells are often prolonged into spines or other projections, which are sometimes arranged in such a manner as to give them a very singular aspect (fig. 4.) It seems probable that these creatures are at the present time as widely diffused as the Foraminifera, although, from their extreme minuteness, they have not been so often recognized. They were first discovered by Professor Ehrenberg at Cuxhaven, on the North Sea; they were afterwards found by him in collections made in the Antarctic seas; and have been recently described by Professor Bailey as presenting themselves (with Foraminifera and Diatomaceae) in the deso that 1631 species of these minute organisms have already been distinguished by classical naturalists posits brought up by the sounding-lead from the bottom of the Atlantic Ocean at depths of from 1000 to 2000 fathoms. They appear to have been much more abundant, however, during the later geological periods, inasmuch as in a single deposit in Barbadoes, Professor Ehrenberg detected no fewer than 282 forms which he considers to be specifically distinct.