. The biology of the protozoa. Protozoa; Protozoa. INTRODUCTION 31 a tendency to become globular and this is the form assumed by the great majority of Protozoa when they encyst. The spherical or homaxonic type, furthermore, is characteristic, not only of free floating forms, but also of the most generalized representatives of all classes of Protozoa. While density or consistency of the protoplasm is thus one of the factors determining form in Protozoa, its effect in the majority of types is offset by the presence of definite membranes, shells, tests and skeletons; by specialized protoplasmic d
. The biology of the protozoa. Protozoa; Protozoa. INTRODUCTION 31 a tendency to become globular and this is the form assumed by the great majority of Protozoa when they encyst. The spherical or homaxonic type, furthermore, is characteristic, not only of free floating forms, but also of the most generalized representatives of all classes of Protozoa. While density or consistency of the protoplasm is thus one of the factors determining form in Protozoa, its effect in the majority of types is offset by the presence of definite membranes, shells, tests and skeletons; by specialized protoplasmic differentiations; or by foreign bodies. Thus the density of the sluggish Pelomyxa palustris. Fig. 9.—Euglypha alveolala (A), and Cochliopodium, sp. (B). (After Calkins.) is due to the enormous number of crystals of mud and sand, shells of diatoms and peculiar refractile bodies resembling glycogen in make up. Membranes of living substance, as in Cochlioyodium (Fig. 9) and the majority of flagellates and ciliates, of lifeless chitin as in Allogromia oviforme (Fig. 10) or the lifeless materials secreted by the cell and deposited on it are responsible for the forms assumed by many Protozoa. Even delicate types such as Clathrvlina elegans and the majority of Heliozoa retain their forms by virtue of the protecting shells of lifeless materials deposited on a chitinous mem- brane. The protoplasmic bodies of many of the fresh water shelled. 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 Calkins, Gary N. (Gary Nathan), b. 1869. Philadelphia, Lea & Febiger
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