. Elementary text-book of zoology. Zoology. 190 PROTOZOA. (fig. 130). A fine peripheral framework of spicules may be added to these. In other cases simple or compound lattice-works, and pierced shells of various external form (like helmets, bird-cages, shells, etc.) are found, and on the periphery of these, spicules and needles, and even external concentric shells of similar shape may be formed, , Polycystina (figs. 131 and 132). Up to the present time but little has been made out about the reproduction of these animals. Besides fission (Polycyttaria), the formation of germs has been obser
. Elementary text-book of zoology. Zoology. 190 PROTOZOA. (fig. 130). A fine peripheral framework of spicules may be added to these. In other cases simple or compound lattice-works, and pierced shells of various external form (like helmets, bird-cages, shells, etc.) are found, and on the periphery of these, spicules and needles, and even external concentric shells of similar shape may be formed, , Polycystina (figs. 131 and 132). Up to the present time but little has been made out about the reproduction of these animals. Besides fission (Polycyttaria), the formation of germs has been observed. These are formed from the contents of the central capsule, and, after the bursting of the latter, become free-swimming mastigopods. Radiolaria are inhabitants of the sea, and swim at the surface, but are also able to sink to deeper levels. Fossil remains of Ra- diolaria have been made knowrn in great numbers by Ehrenberg, from the chalky marl and polishing slate found at certain parts of the coast of the Mediterranean (Caltanisetta in Sicily, Zante and ^Egina in Greece), and in particu- lar from the rocks of Barbados and Nikobar, where the Radiolaria have given rise to widely extended rock formations. Samples of sand also from very con- siderable depths have shown themselves rich in Radiolarian shells. I. Radiolaria monozoa. Radiolaria which remain solitary. 1. Fam. Thalassicollidae. Skeleton absent or consisting of single spicules not joined together. Tlialaxsicolla (without skeleton) undentti Plnjste- mat-ium Mullen Schn. 2. Fam. Polycystinidoe. The skeleton consists of a simple or divided latticed shell, the long axis of which is bounded by two poles of different structure. Ifdioapliffrn. Euryrtidiuin ijnlr<i E. Haeck. 3. Fam. Acanthometridae. The skeleton consists of several radial spicules •which pass through the central capsule and unite in its centre, without forming. FIG. \"S\..—\io»p1i<era echinoides (after E. Haeckel).. Please note
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1884
