. A manual of zoology. PHYLUM PROTOZOA 31 subsequently become lost, pseudopodia appearing in their place. The Radiolaria are marine Rhizopoda which have exceed- ingly delicate, thread-like pseudopodia (Fig. 9, psd) and a skeleton usually composed of silica. This skeleton may be composed of loosely woven needle-like bodies or spicules; more usually it is in the form of a globular, conical, star- shaped, or disc-shaped shell, perforated by numerous open- ings, and often supported by spines which radiate out from cent caps Fig. 9. — Liteocircus annularis, cent, caps,
. A manual of zoology. PHYLUM PROTOZOA 31 subsequently become lost, pseudopodia appearing in their place. The Radiolaria are marine Rhizopoda which have exceed- ingly delicate, thread-like pseudopodia (Fig. 9, psd) and a skeleton usually composed of silica. This skeleton may be composed of loosely woven needle-like bodies or spicules; more usually it is in the form of a globular, conical, star- shaped, or disc-shaped shell, perforated by numerous open- ings, and often supported by spines which radiate out from cent caps Fig. 9. — Liteocircus annularis, cent, caps, central capsule; cxt. caps, pr, extra- capsular protoplasm; int. caps, pr, intra-capsular protoplasm; nn, nucleus; psd, pseudopods; skel, skeleton; z, cells of Zooxanthella. (After Butschli, from Parker's Biology.) the centre; sometimes (Fig. 10) there are several such shells one within the other. In some Radiolaria the skele- ton is composed not of silica, but of a chitinoid substance called acanthin. Embedded in the protoplasm is a perfor- ated membranous sac, the central capsule (Figs. 9 and 10, cent, caps), in the protoplasm within which is a single nucleus or a number of nuclei, and a number of oil-drops. There is no contractile vacuole, but in many Radiolaria the protoplasm outside the central capsule contains numerous non-contractile vacuoles, the presence of which gives it a frothy Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Parker, T. Jeffery (Thomas Jeffery), 1850-1897; Haswell, William A. (William Aitcheson), 1854-1925. New York, The Macmillan Company; London, Macmillan & Co. ,Ltd.
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