Different explanations of the bilateral symmetry of Rugosa corals

Abstract

In the bilateral symmetry of Rugosa corals, what first catches the eye and prompts one to seek an explanation is the external form of the coral—a cone bent like a horn. Neumayr (Die Stämme des Thierreichs) already points to this form as characteristic of the entire Rugosa group. In the explanation I have given of the structure of Rugosa, I proceeded from the fact, which I established for the first time, of the lateral attachment of Rugosa corals, so that in this respect there is some similarity with Bernard's hypothesis. However, I proceeded from the fact of lateral attachment, which I have firmly established—this attachment being primary, and not secondary as in Bernard's view, according to whose hypothesis lateral attachment replaces an initial axial attachment, occurring as if by truncation of the pointed end.

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