The Allogromidiaceae are a well-marked and distinct order, on the whole resembling the Rhizopoda Filosa, and are often found with them in fresh water, while all other Foraminifera are marine. The type genus, _Allogromia_ (Fig. 14, 1), has an oval chitinous shell. _Microgromia socialis_ (Fig. 11) is often found in aggregates, the pseudopodia of neighbours fusing where they meet into a {60}common network. This is due to the fact that one of the two daughter-cells at each fission, that does not retain the parent shell, remains in connexion with its sister that does: sometimes, however, it retracts its pseudopodia, except two which become flagella, wherewith it can swim off. The test of _Pamphagus_ is a mere pellicle. In _Lieberkühnia_ (Fig. 12) it is hardly that; though the body does not give off the fine pseudopodia directly, but emits a thick process or "stylopodium"[78] comparable to the protoplasm protruded through the pylome of its better protected allies; and from this, which often stretches back parallel to the elongated body, the reticulum of pseudopodia is emitted. _Diaphorodon_ has a shell recalling that of _Difflugia_ (Fig. 10, D, p. 55), formed of sandy fragments, but with interstices between them through which as well as through the two pylomes the pseudopodia pass. In all of these the shell is formed as in the Rhizopods once for all, and does not grow afterwards; and the fresh-water forms, which are the majority, have one or more contractile vacuoles; in _Allogromia_ they are very numerous, scattered on the expanded protoplasmic network. [Illustration: FIG. 11.—_Microgromia socialis._ A, entire colony; B, single zooid; C, zooid which has undergone binary fission, with one of the daughter-cells creeping out of the shell; D, flagellula. _c.vac_, Contractile vacuole; _nu_, nucleus; _sh_, shell. (From Parker and Haswell, after Hertwig and Lesser.)] {61}[Illustration: FIG. 12.—_Lieberkühnia_, a fresh-water Rhizopod, from the egg-shaped shell of which branched pseudopodial filaments protrude. (From Verworn.)]