. Protozoo?logy. Protozoa; Protozoa, Pathogenic. 72 PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA which take place in the plant's protoplasm. Animals solve the problem of nutrition by living on plants, or by eating other animals which, either directly'or indirectly, live on plants. Still other types live as parasites upon other animals, some, like the intestinal worms, using freely the foods that are prepared by, and for the use of, the host, while others, like some insects, suck the blood, or, like trichina, invade the cells and tissues, and live at the expense of the living protoplasm. In the gro
. Protozoo?logy. Protozoa; Protozoa, Pathogenic. 72 PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA which take place in the plant's protoplasm. Animals solve the problem of nutrition by living on plants, or by eating other animals which, either directly'or indirectly, live on plants. Still other types live as parasites upon other animals, some, like the intestinal worms, using freely the foods that are prepared by, and for the use of, the host, while others, like some insects, suck the blood, or, like trichina, invade the cells and tissues, and live at the expense of the living protoplasm. In the group of protozoa all of these methods of food getting are found. Many forms possess chlorophyl, and like the green plants,. Synura u\-ella, a colony of phytoflagellates, often a source of disagreeable odors and tastes in drinking waters. (After Calkins.) manufacture their food directly from simple elements. These protozoa, are of considerable theoretical interest, for they stand upon the border- line between the animal and the plant kingdoms, and are sometimes classed as one, sometimes as the other. They are thus involved in what has been one of the most contested of biological problems, the limits of the animal and plant kingdoms, and the problem is the more difficult because some types of this intermediate group may on occa- sions make their food, while at other times they eat like undoubted animals and take in solid food (Chromulina Jiaricans, and some forms of dinoflagellata). The problem has but little signifit'ance in the present. 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. New York and Philadelphia, Lea & Febiger
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