[Illustration: Fig. 25.--The animal of _Nonionina_, one of the _Foraminifera_, after the shell has been removed by a weak acid; b, _Gromia_, a single-chambered Foraminifer (after Schultze), showing the shell surrounded by a network of filaments derived from the body substance.] [Illustration: Fig 26.--Shells of living _Foraminifera_. a, _Orbulina universa_, in its perfect condition, showing the tubular spines which radiate from the surface of the shell; b, _Globigerina bulloides_, in its ordinary condition, the thin hollow spines which are attached to the shell when perfect having been broken off; c, Textularia variabilis; d, Peneroplis planatus; e, Rotalia concamerata; f, _Cristellaria subarcuatula._ [Fig. a is after Wyville Thomson; the others are after Williamson. All the figures are greatly enlarged.]] Such, in brief, is the structure of the living _Foraminifera_; and it is believed that in _Eozoön_ we have an extinct example of the same group, not only of special interest from its immemorial antiquity, but hardly less striking from its gigantic dimensions. In its original condition, the entire chamber-system of _Eozoön_ is believed to have been filled with soft structureless living matter, which passed from chamber to chamber through the wide apertures connecting these cavities, and from tier to tier by means of the tubuli in the shell-wall and the branching canals in the intermediate skeleton. Through the perforated shell-wall covering the outer surface the soft body-substance flowed out, forming a gelatinous investment, from every point of which radiated an interlacing net of delicate filaments, providing nourishment for the entire colony. In its present state, as before said, all the cavities originally occupied by the body-substance have been filled with some mineral substance, generally with one of the silicates of magnesia; and it has been asserted that this fact militates strongly against the organic nature of _Eozoön_, if not absolutely disproving it. As a matter of fact, however--as previously noticed--it is by no means very uncommon at the present day to find the shells of living species of _Foraminifera_ in which all the cavities primitively occupied by the body-substance, down to the minutest pores and canals, have been similarly injected by some analogous silicate, such as glauconite.