INTEGRATION AND SYMMETRY IN BEROE

Despite the fact that certain prominent structures such as theeight comb-rows at first suggest an octomerous radial symmetryin ctenophores, close examination of their anatomy reveals ratherthe existence of two main planes, the sagittal and the transverse.Further, in certain forms in which one plane or the other hasbecome predominant, an apparent bilateral symmetry emerges. Relationships between anatomical and physiological symmetrywere looked for by studying the behavior of Beroe ovata andBeroe forskalii, both with regard to coordinated ciliary movementsbetween the comb-rows, and to the postures assumed during locomotion,balance, and rest in intact animals, and in animals from whichthe aboral organ had been removed. Swimming behavior is found to exhibit an octomerous functionalsymmetry. Bendings and vertical balance, however, show a tetramerousorganization. In the last case the unique properties of thestatocyst, with a structure characteristic of a regulator ofcybernetic patterns, the machines of which are the comb-rows,permit the most efficient integration of all the phenomena involvedin maintaining the vertical position. Finally the resting horizontalposition reflects a physiological bilateral symmetry basic tothe sagittal plane.