Page:Natural History Review (1861).djvu/473

Rh work is produced that might be almost described as an animated spider's web. Any small alimentary particles that may come into contact with the glutinous surface of the pseudopodia are retained in adhesion by it, and speedily partake of the general movement going on in their substance. This movement takes place, in two principal directions; from the body towards the extremities of the pseudopodia, and from these extremities back to the body again. In the larger branches a double current may be seen, two streams passing at the same time in opposite directions; but in the liner filaments the current is single, and a granule may be seen to move in one of them to its very extremity, and then to return, perhaps meeting and carrying back with it a granule that was seen advancing in the opposite extremity. Even in the broader processes, granules are sometimes observed to come to a stand, to oscillate for a time, and then to take a retrograde course, as if they had been entangled in the opposing current,—just as is often to be seen in Chara. When a granule arrives at a point where a filament bifurcates, it is often arrested for a time until drawn into one or the other current; and when carried across one of the bridge-like connections into a different band, it not unfrequently meets a current proceeding in the opposite direction, and is thus carried back to the body without having proceeded very- far from it. The pseudopodian network along which this "cyclosis" takes place is continually undergoing changes in its own arrangement; new filaments being put forth in different directions, sometimes from its margin, sometimes from the midst of its ramifications, whilst others are retracted. Not unfrequently it happens, that to a spot where two or more filaments have met, there is an Influx of the protoplasmic substance, which causes it to accumulate there as a sort of secondary centre, from which a new radiation of filamentous processes takes place.

Now, the entire absence of differentiation in the protoplasmic substance, the freedom of the mutual inosculation of its pseudopodian extensions, and the active cyclosis incessantly going on between these and the body, are three mutually related conditions, which not only serve to characterize the group of animals that exhibits them, but, as we shall presently see, to differentiate that group from others. There is, moreover, a negative character of much importance, which is naturally associated with the absence of differentiation,—namely, the deficiency of the "nucleus" and "contractile vesicle" that occur both in Actinophrys and in Amœba. So far as is yet known, there is a perfect agreement as to all these characters between the Foraminifera and the Gromida; and I regard Lieberkühnia as standing in the same relation to the chitine-covered Gromia or to the calcareous-shelled Foraminifera, that Actinophrys does to the chitine-covered Euglypha or to the siliceous-shelled Polycystina. The entire group thus constituted may (as it appears to me) be appropriately termed ; the ordinal designation being meant to express that reticulose arrangement of the pseudopodian extensions which is its distinguishing characteristic.