General physiology; an outline of the science of life . ssential features inthe ontogeny as in the phylogeny. It remains for the embryology of the future to discoverin detail the very manifold special relations, which are as differentas the organisms themselves. While the mechanical causes of cell-differentiation in the com-plicated cell-community must be sought in changes of its relationswith the environment, which for every cell and cell-generation aredue to continued cell-division, division of labour among the cells isbased upon the development of the cell-community itself.1 The workof ever

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General physiology; an outline of the science of life . ssential features inthe ontogeny as in the phylogeny. It remains for the embryology of the future to discoverin detail the very manifold special relations, which are as differentas the organisms themselves. While the mechanical causes of cell-differentiation in the com-plicated cell-community must be sought in changes of its relationswith the environment, which for every cell and cell-generation aredue to continued cell-division, division of labour among the cells isbased upon the development of the cell-community itself.1 The workof ever
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Image ID: 2AJJT0J
General physiology; an outline of the science of life . ssential features inthe ontogeny as in the phylogeny. It remains for the embryology of the future to discoverin detail the very manifold special relations, which are as differentas the organisms themselves. While the mechanical causes of cell-differentiation in the com-plicated cell-community must be sought in changes of its relationswith the environment, which for every cell and cell-generation aredue to continued cell-division, division of labour among the cells isbased upon the development of the cell-community itself.1 The workof every multicellular organism is the expression of the activity ofits individual cells. If the cells are different, they contribute in adifferent manner to the whole labour of the organism. That thiscombined labour must become harmonious and advantageousfollows from the principle of selection, which controls all organic-development, phylogenetic as well as ontogenetic. Only thosecell-communities continue to live, in which the cell-generations 1 Of. p. 536.. Fio. 277.—Protospoagia Hceckdii. (After Lang.) 576 GENERAL PHYSIOLOGY arising from the continued division of the egg-cell are in harmonywith the special conditions under which they appear. All inwhich this is not the case must perish in the struggle for existencethrough the action of selection. But the most complete harmonyis reached when the individual labours of the different cells so fitinto one another that, although every cell or cell-group has de-veloped a different labour for its own specialty, this labour is forthe good of all the other cells, is, indeed, necessary to all theothers. Thus, the extraordinarily far-reaching differentiation andsurprisingly detailed division of labour of the individual cells andtissues in the cell-community become comprehensible. As a result of the division of labour, every kind of cell, everytissue, every organ in the multicellular community undertakesa special task, and since early times p