INTEGRATION AND SYMMETRY INBEROE

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Abstract
Despite the fact that certain prominent structures such as the eight comb-rows at first suggest an octomerous radial symmetry in ctenophores, close examination of their anatomy reveals rather the existence of two main planes, the sagittal and the transverse. Further, in certain forms in which one plane or the other has become predominant, an apparent bilateral symmetry emerges. Relationships between anatomical and physiological symmetry were looked for by studying the behavior of Beroe ovata and Beroe forskalii, both with regard to coordinated ciliary movements between the comb-rows, and to the postures assumed during locomotion, balance, and rest in intact animals, and in animals from which the aboral organ had been removed. Swimming behavior is found to exhibit an octomerous functional symmetry. Bendings and vertical balance, however, show a tetramerous organization. In the last case the unique properties of the statocyst, with a structure characteristic of a regulator of cybernetic patterns, the machines of which are the comb-rows, permit the most efficient integration of all the phenomena involved in maintaining the vertical position. Finally the resting horizontal position reflects a physiological bilateral symmetry basic to the sagittal plane.

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