. Protozoo?logy. Protozoa; Protozoa, Pathogenic. 26 GENERAL ORGANIZATION OF THE PROTOZOA (c) Plastids.—In addition to the basic substances making up the fluid protoplasm there are larger or smaller granules of different kinds embedded in the alveolar or interalveolar material; these granules may be food particles ready for assimilation, waste particles waiting for excretion, metaplasmic particles like oil drops, pigment grains, and the like, or foreign particles like sand grains, calcium, sihca, etc., to be used in building shells or stalks. The plastids that are formed in a great many protozo
. Protozoo?logy. Protozoa; Protozoa, Pathogenic. 26 GENERAL ORGANIZATION OF THE PROTOZOA (c) Plastids.—In addition to the basic substances making up the fluid protoplasm there are larger or smaller granules of different kinds embedded in the alveolar or interalveolar material; these granules may be food particles ready for assimilation, waste particles waiting for excretion, metaplasmic particles like oil drops, pigment grains, and the like, or foreign particles like sand grains, calcium, sihca, etc., to be used in building shells or stalks. The plastids that are formed in a great many protozoa, especially in those types which lie on the boundary line between the lower plants and the protozoa, may have a considerable economic importance. Many of them are starchy in nature, i. e., formed products to be used Fig. 9. A complex polythalamous shell (schematic) of Operculina. (After Carpenter.) The shell is represented as cut in different planes to show the distribution of the canals (a', a", a'"); c, c, c, the outer chambers with double walls (d, d, d), one of which is shown in section (g). The chambers communicate by apertures at the inner ends of the septa (e), and by minute pores (/). The outside (&) of the shell is marked by the radial septa. as food; others are starch-forming centres or pyrenoids, which are usually embedded in plastids of large size, called chromatophores from the color they possess. These colors, due to some form of chlorophyl, may be bright green like the foliage of higher plants, or red, orange, yellow, brown, or black, according to the nature of the materials which combine with the chlorophyl. When great numbers of these color- bearing protozoa are massed together the result is a brilliantly colored area; red snow, for example, being due to aggregates of hematococ- cus, the red coming from the color of the minute chromatophore in each small cell. Similarly, great patches on the sea may be colored presence of noctiluca, or red by
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