COÖRDINATION AND MOVEMENT OF THE SWIMMING-PLATES OF MNEMIOPSIS LEIDYI, AGASSIZ

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Abstract
1. The apical organ in the aboral zone is the center from which impulses travel out into the plate rows. 2. The aboral impulses synchronize the plate movements in all eight rows except during slow movements. 3. At low rates of plate beating each row becomes independent. 4. The synchronism in the plate rows of a quadrant as a unit is more persistent than in the eight plate rows as a unit. 5. The highest type of synchronized unit is demonstrated by a single plate row. 6. A single plate row beating independently of other plate rows, whether normally located on the animal or detached from it, exhibits an aboral dominance. 7. Swimming plates do not reverse either their metachronal or effective beat while located naturally on the animal. 8. Swimming plates reverse their effective beat on isolated pieces of plate rows, but they do not reverse their metachronal wave. 9. Dilute solutions of methylene blue show the interplate structures in the plate rows to be entirely granular in nature without exhibiting any cellular elements. 10. The coördinating System of Mnemiopsis is demonstrated more definitely by physiological tests than by staining results. This system is superficially located along the plate rows. The fact that single isolated plates show a certain amount of autonomy and the fact that transmission in a plate row is immediately reëstablished following its interruption as produced by a cut show this system to be much more localized than has been heretofore believed.

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