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On the Classification of Actiniaria: Part I.—Forms with Acontia and Forms with a Mesoglœal Sphincter

1920; The Company of Biologists; Volume: S2-64; Issue: 256 Linguagem: Inglês

10.1242/jcs.s2-64.256.425

1477-9137

T. A. Stephenson,

Coral and Marine Ecosystems Studies

ABSTRACT Whilst working out recently the species contained in two collections of Actiniaria (the “Terra Nova” collection (79)1 and one made by the Irish Fisheries Department (80)) , I have been led to develop certain views on Actinian classification. Some of the families of Actiniaria are defined by only a small number of the more important characters possessed by the contained forms, with the result that some of them (e. g. Uyanthidæ, Sagartiidæ, Paractidæ) represent not so much families as series of forms, each series including a number of animals which differ among themselves in ways so important as to be fundamental, although presenting a few common features. This arrangement neither represents the natural affinities of the genera nor does it throw much light upon their evolutionary history. It is often difficult also to allocate new species and genera to their correct position, because in a good many cases sufficiently precise generic definitions have not been arrived at. I have therefore thought it would be the best thing to set out for what they are worth the ideas I have developed during the course of my work. I have as yet applied them in detail to only one particular portion of the Actiniaria, and that application constitutes the following paper. I have begun with the group of forms belonging to the Actiniina which possess acontia or mesoglœal sphincters, because the collections I have been working at happened to present a preponderance of those forms ; I am also well acquainted with some living members of it. I am hoping in due course to work out schemes on similar lines for the classification of those Actiniina not included in the present paper and of the Stichodactylina. As yet, however, I have made only a beginning on the two latter groups, so am publishing the finished section at once. More work on these two groups may throw fresh light on various Actinian problems, but is not very likely, I think, to affect the section dealt with in this paper to any extent.