. Animal biology. Biology; Zoology; Physiology. THE MULTICELLULAR ANIMAL 59 marshalled to perform a certain function. The power of a muscle results from the combined action of its component muscle cells. Differentiation without cooperation between cells we have seen in unicellular organisms. Paramecium has highly specialized parts; other Protozoa have still more — perhaps the limit of possi-. Fig. 30. — Volvox globator, a large colony of flagellated unicellular organ- isms in which the various cells have become organically connected, and certain cells specialized for reproduction. (Highly magn
. Animal biology. Biology; Zoology; Physiology. THE MULTICELLULAR ANIMAL 59 marshalled to perform a certain function. The power of a muscle results from the combined action of its component muscle cells. Differentiation without cooperation between cells we have seen in unicellular organisms. Paramecium has highly specialized parts; other Protozoa have still more — perhaps the limit of possi-. Fig. 30. — Volvox globator, a large colony of flagellated unicellular organ- isms in which the various cells have become organically connected, and certain cells specialized for reproduction. (Highly magnified.) A, mature colony (highly magnified) showing sperm, d\ and eggs, 9, in various stages of de- velopment; B, four cells (more highly magnified) showing the connections between three 'somatic' cells, and the early differentiation of a reproductive cell, rp. cv, contractile vacuole; st, 'eyespot' or stigma. (From Kolliker.) bilities of the single cell. But the multicellular body solves the difficulty by removing the limit — by assigning special functions to groups of cells rather than to parts of one cell. Thus cell division (cleavage) involving growth, differentiation, and its attendant physiological division of labor is the keynote of development in the higher animals and plants. Among animals, the cells which arise from the cleaving egg (zygote) usually become. 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 Woodruff, Lorande Loss, 1879-1947. New York The Macmillan company
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