. An introduction to zoology : for the use of high schools . na and similar pelagic forms being raineddown upon the bottom. 16. The pseudopodia in the Rhizopoda may flow togetherround a particle of food as represented in Fig. 190, but in theremaining orders of Sarcodina, they are less subject to altera-tion in form, rarely coalesce, stand out radially from the body,and are sometimes strengthened by an axial filament. Theseorders are the Heliozoa and the Radiolaria, the former a smallgroup, chiefly of fresh-water forms, sometimes naked, sometimeswith a spicular or perforated shell (Fig. 189, e)
. An introduction to zoology : for the use of high schools . na and similar pelagic forms being raineddown upon the bottom. 16. The pseudopodia in the Rhizopoda may flow togetherround a particle of food as represented in Fig. 190, but in theremaining orders of Sarcodina, they are less subject to altera-tion in form, rarely coalesce, stand out radially from the body,and are sometimes strengthened by an axial filament. Theseorders are the Heliozoa and the Radiolaria, the former a smallgroup, chiefly of fresh-water forms, sometimes naked, sometimeswith a spicular or perforated shell (Fig. 189, e) ; the latter, a ma-rme group containing numerous forms with siliceous skeletons,which offer the most surprising beauty and wealth of form (). The Radiolaria are afeo important from a geological,l)oint of view, for deposits of infusorial earth are foundconsisting almost entirely of their shells, and similar depositsare being formed in some parts of the ocean at the present body is more differentiated than in the Heliozoa, the endo- vyw-:*^ L. ¥v^. 191.—Living Radiolarian :—Heliosphcera actinota. 256 HlGfi SCHOOL ZOOLOGY. plasm being separated off by a special central capsule fromthe ectoplasm. In the latter there are often found minute yel-low Algfe, which appear to live symbiotically with the Ra-diolaiia. 17. The Sporozoa are distinguished frc m the Rhizopoda notonly by the absence of pseudo])odia,but by the presence of a well-marked cuticle which limits the contractions of the protoplasm ;they reproduce by spores, formed by the simultaneous divisionof the plasma of an encystely in epithelial or blood-cellsof both lower and higher animals, and others, finally, ectopara-sites of fish, being found on the gill-filaments. The spores ofthe last fo
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1889
