Its consistence is variable; it is composed of minute globules, the aggregation of which determines the general tint. It is sometimes entire, round, and without segments, as in _Gromia_, _Orbulina_, &c., which represent at all ages the embryonic state of all the other genera. The animal increases by gemmation, each segment being essentially distinct, but connected with the preceding one by a tube or neck. When the body is divided by lobes or segments, the primary lobe, as in the permanent condition of the Gromia, is at first round or oval, according to the genus; once formed it never enlarges, but is enveloped externally by testaceous matter. The segments, which successively appear, are agglomerated together in seven different ways, and these modifications are the basis of M. D'Orbigny's classification. The discoidal forms, as the _Rotalia_, _Rosalina_, _Cristellaria_, &c. are involute, like the Nautilus, and divided by septa or partitions, which, like the enveloping shell, are perforated. The lobes of the body _occupy contemporaneously every chamber_, and are connected by a tube that extends through the entire series. In the spiral form, as the Textularia, &c., the same structure is apparent. Whatever the form of the body, the filaments always consist of a colourless transparent matter; they are capable of being elongated to six times the diameter of the shell. They often divide and subdivide, so as to appear branched; and though alike in form in the different genera, vary much in their position. In some species they form a bundle which issues from a single aperture, and is withdrawn into the same by contraction; in others, the filaments project only through each of the pores in that portion of the shell which covers the last segment: in many they issue from both the large aperture and the foramina. These filaments or pseudopodia fulfil in these animals the functions of the numerous tentacula in the Star-fishes; serving as instruments of locomotion and attachment. Neither organs of nutriment nor of reproduction have been discovered. In the genera having one large aperture from which the filaments issue and retract, we can conceive nutriment to be absorbed by that opening; but this cannot be the case in the species which have the last cell closed up; in these the filaments issuing through the foramina are probably also organs of nutrition. M. D'Orbigny considers the Foraminifera as constituting a distinct class in zoology; though less complicated than the Echinoderms and the Polypifera in their internal organization, they have the mode of locomotion of the first; while by their free, individual existence, they are more advanced in the scale of being than the aggregated and immovably fixed animals of the latter class.