Text-book of comparative anatomy . s differentiated into two ventral symmetrical mesoderm streaks,which unite posteriorly (at the edge of the blastopore) in a median zone, and in this VI PROTRACHEATA 435 /one, throughout embryonic development, active processes of growth go on. Besidesthis the cell material of the two mesoderm streaks themselves increases by a continuousprocess of division. Segmental cavities appear in the mesoderm streaks in continuoussuccession from before backward, and these separate into mesoderm segments ormesoderm sacs with walls, which are at first unilaminar. The furthe
Text-book of comparative anatomy . s differentiated into two ventral symmetrical mesoderm streaks,which unite posteriorly (at the edge of the blastopore) in a median zone, and in this VI PROTRACHEATA 435 /one, throughout embryonic development, active processes of growth go on. Besidesthis the cell material of the two mesoderm streaks themselves increases by a continuousprocess of division. Segmental cavities appear in the mesoderm streaks in continuoussuccession from before backward, and these separate into mesoderm segments ormesoderm sacs with walls, which are at first unilaminar. The further differentiationof these mesoderm sacs occurs in such a way that each falls into three cavities, oneof which becomes the nephridial funnel (Fig. 2S9, A-C) while the others disappear asdistinct cavities, and the cell material of their walls yields the mesodermal por-tions (endothelium, muscles, connective tissue) of the trunk and of the extremities arise as outgrowths of the body wall. The first pair of rudimentary.
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanatomycomparative
