Marcus Manuel Hartog

“ The animal usually forms a simple shell only after it has attained a certain size, and this “embryonic chamber” cannot grow further. In Spirillina and Ammodiscus there is no pylomic end-wall, and the shell continues to grow as a spiral tube; in Cornuspira (fig. 3, 1) there is a slight constriction indicating the junction of a small embryonic chamber with a camptopyle, but the rest of the shell is a simple flat spiral of several turns. In the majority at least one chamber follows the first, with its own pylome at the distal end. ”

“ 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 ”

“ Calcituba, a porcellanous type, which after forming the embryonic chamber with its deflected pylome grows into branching stems, may fall apart into sections, or the protoplasm may escape and break up into small amoebulae. Of the reproduction of the simplest forms we know little. In Mikrogromia the cell undergoes fission within the test, and on its completion the daughter-cells may emerge as biflagellate zoospores. ”

“ F. Schaudinn compares the nuclei of the adult Foraminifera with the (vegetative) meganucleus of Infusora (q.v.) and the chromidial mass with the micronucleus, whose chief function is reproductive.
Since megalospheric forms are by far the most abundant, it seems probable that under most conditions they also give rise to megalospheric young like themselves; and that the production of zoospores, pairing to pass into the microspheric form, is only occasional, and possibly seasonal. This life-history we owe to the researches of Schaudinn and J.J. Lister. ”

“ 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. ”

“ The adult microspheric animal gives rise to the amoebiform brood which have a larger primitive test (“megalosphere”) ; and megalospheric forms appear to reproduce by the A type a series of similar forms before a B brood of gametes is finally borne, to pair and reproduce the microspheric type, which is consequently rare. ”

“ Appendix.—The Xenophyophoridae are a small group of bottom-dwelling Sarcodina which show a certain resemblance to arenaceous Foraminifera, though observations in the living state show that the character of the pseudopodia is lacking. The multinucleate protoplasm is contained in branching tubes, aggregated into masses of definite form, bounded by a common wall of foreign bodies (sponge spicules, &c.) cemented into a membrane. The cytoplasm contains granules of BaSO4 and pellets of faecal matter. All that is known of reproduction is the resolution of the pellets into uninucleate cells. ”

“ Protoplasmic Body and Reproduction.—The protoplasm is not differentiated into ecto- and endosarc, although it is often denser in the central part within the shell, and clearer in the pseudopodial ramifications and the layer (or stalk in the monothalamic forms) from which it is given off. In pelagic forms like Globigerina the external layer is almost if not quite identical in structure with the extracapsular protoplasm of Radiolaria (q.v.) ”

“ Nummulites occur in English beds and in the Paris basin; but the great beds of these, forming reef-like masses of limestone, occur farther south, extending from the Pyrenees through the southern and eastern Alps to Egypt, Sinai, and on to north India. ”