Page:Encyclopædia Britannica, Ninth Edition, v. 19.djvu/874

Rh 850 PROTOZOA [RADIOLARIA. Fam. 3. THALASSICOLLIDA. Peripyhea devoid of a skeleton, or with a skeleton composed ol&quot; loose siliceous spieules only. Nucleus single ; oentral capsule and general protoplasm spherical. Genera (selected). Thalasaicolla, Huxley (Fig. XIII., Fig. XIV. 1); Thalasaosphsera, Hacck. ; Physematium, Haeck. Fain. 4. POLYCYTTAKIA. Peripylwa consisting of colonies of many central capsules united by their extracapsular protoplasm. Central capsules multiplying by fission. Nuclei in each central capsule numerous. Siliceous skeleton either absent, or of loose spicules, or having the form of a spherical fenestrated shell sur rounding each central capsule. ( Jenera (selected). Collosph&ra, Miiller (with fenestrated globular intrme, Bbowlng the iiitracapsular protoplasm and nucleus, u wen up into a number of spores, the gerrns of swarm -spores or flagellulte each encloses a crystalline rod. c, yellow cells lying in the extracapsular protoplasm. 5. A small colony of Collozonm inrrme, magnified 25 diameters, a, alveoli (vacuoles) of the extracapsular protoplasm ; b, central capsules, each containing besides protoplasm a large oil-globule. (V-13. Yellow cells of various Radiolaria : 6, normal yellow cell; 7, 8. division with formation of transverse septum; 9, a modified condition according to Brandt ; 10, division of a yellow cell into four ; 11, ama boid condition of a yellow cell from the body of a dead Sph;erozoon ; 12, a similar cell in process of division ; 13, a yellow cell the protoplasm of which is creeping out of its cellulose envelope. 14. Jltliogphxru ini nnis, Haeck., living example; x 400. &amp;lt;r, nucleus ; 6, central capsule ; c, siliceous basket-work skeleton. lii. Two swarm-spores (Hagellul.T) of Collozoum inerme, set free from such a central capsule as that drawn in 4 ; each contains a crystal b and a nucleus . 16. Two swarm-spores of Collozoum inerme, of the second kind, viz., devoid of crystals, and of two sizes, a macrosporc and a microspore. They have been set free from central capsules with contents of a different appearance from that drawn in 4. a, nucleus. 17. Actinonnna asteracanthion, Haeck ; x 2(50; one of the J eripylsea. Entire animal in optical section, a, nucleus ; b, wall of the central capsule ; c, innermost siliceous shell enclosed in the nucleus ; c 1, middle shell lying within the central capsule ; c 2 , outer shell lying in the extracapsular protoplasm. Four radial siliceous spines, hold ing the three spherical shells together are seen. The radial fibrillation of the protoplasm and the flue extracapsular pseudopodia are to be noted. 18. Amphilonche messanensig, Haeck; x 200; one of the Acanthometridea. Entire animal as seen living. OKDER 2. MOXOPYL;EA, Hertwig. Characters. Silico-skeletal Radiolaria in which the central cap sule is not spherical but monaxonic (cone-shaped), with a single per forate area (pore-plate) placed on the basal face of the cone ; the membrane of the capsule is simple, the nucleus single ; the skeleton is extracapsular, and forms a scaffold-like or bee-hive-like structure of iiionaxoiiic form. Fio. XV. Eucyrtidium cranioides, Haeck ; x 150 ; one of the Monopyhea. Entire animal as seen in the living condition. The central capsule is hidden by the bee-hive-shaped siliceous shell within which it is lodged. Fain. 1. PLECTIDA, Haeck. Skeleton formed of siliceous spines loosely conjoined. Genera (selected). Plagiacantha, Haeck. ; Flcymatinm, Hacck. Fam. 2. CYRTIDA, Haeck. Skeleton a nionaxouic or triradiate shell, or continuous piece (bee-hive-shaped). Genera (selected). Halicalyptrn, Hacck. ; Eucyrtidium, Hacck. (Fig. XV.); Carpocanium, Haeck. (Fig. XVI. 3). Fam. 3. BOTKIDA, Haeck. Irregular forms ; the shell composed of several chambers agglomerated without definite order ; a single central capsule. Genera. Botryocyrtis, Haeck. ; LUhobotrys, Haeck. Fam. 4. Si YRiDA, Hacck. Gemrninate forms, with shell con sisting of two conjoined chambers ; a single central capsule. Fam. 5. STEPHIDA-, Haeck. Skeleton cricoid, forming a single siliceous ring or several conjoined rings. Genera (selected). Acanthodcsmia, Haeck. ; Zygostcphanus, Haeck. ; Lithocircus, Hacck. (Fig. XVI. 1). ORDER 3. PH^EODARIA, Hacck. (Tripylsea, Hertwig). Characters. Silico-skeletal Radiolaria in which the central