. Comparative zoology, structural and systematic. For use in schools and colleges. Zoology. 234 COMPARATIVE ZOOLOGY. and the blocks in the Pyramids of Egypt are largely com- posed of extinct Foraminifers. A Poly cystine differs from a Foraminifer in secreting a siliceous, instead of a calcareous, shell, studded with spines; and the central part of the body is made up of many cells, and surrounded by a strong membrane. While Foraminifers live mostly at the bottom of the sea, Polycys- tines generally float on the surface. They are also more minute, but as widely diffused. They enter largely into
. Comparative zoology, structural and systematic. For use in schools and colleges. Zoology. 234 COMPARATIVE ZOOLOGY. and the blocks in the Pyramids of Egypt are largely com- posed of extinct Foraminifers. A Poly cystine differs from a Foraminifer in secreting a siliceous, instead of a calcareous, shell, studded with spines; and the central part of the body is made up of many cells, and surrounded by a strong membrane. While Foraminifers live mostly at the bottom of the sea, Polycys- tines generally float on the surface. They are also more minute, but as widely diffused. They enter largely into the formation of some strata of the earth's crust, and abound especially in the rocks of Barbados and at Rich- mond, Ya. Class III.—Infusoria. This unassorted group of living particles derived its name from the fact that they were first discovered in vegeta- ble infusions. Every drop of a stagnant pool is crowded with them. They are all single and microscopic, yet of various sizes, the differ- ence between the smallest and largest being greater than the difference be- tween a Mouse and an Elephant. Some are fixed (as Vorticella)', but the major- ity are free, and constantly in motion, propelled by countless cilia, as a galley by its oars. The delicate body consists of unorganized sarcode {i. e., there are no cellular tissues, but the whole body represents a single cell), covered by a membrane, or skin, and containing a semi-fluid substance, a contractile cavity, and several. Fig. 1S2.—a Compound Monad {(Ivella), X 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 Orton, James, 1830-1877. New York, Harper and brothers
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