The Peridiniales

Abstract

DURING the cruise of the non-magnetic ship Carnegie of the Departmentof Terrestrial Magnetism of the Carnegie Institution of Washington in 1928–29 intensive studies were carried out in the Pacific and North Atlantic Oceans, and, combined with the primary oceanographic investigations, a study was made of the plankton. The simultaneous collecting of samples and taking of hydrographic data afforded exceptional opportunities to study the relations between pelagic organisms and their environment. Among the organisms H. W. Graham selected for special study the difficult group of the Peridiniales, and from a preliminary survey it became evident that no general floristic study was possible in the light of the inadequate knowledge of the group. The peridinian life-histories are incompletely known, so that classification rests upon morphology of the cell, andespecially upon the number and arrangement of the complex series of skeletal plates. On this basis, so far as it is known, Lindemann has described a number of genera, which have been utilized as a basis for the present study*. For description of the plate pattern, Kofoid's terminology has been used, though for the plate formulae abbreviations of the plate names have been found simpler in practice than Kofoid's prime signs. The analysis involves special technique which lies mainly in fixation in formalin, separation of the thecal plates by hypochlorite treatment, and orientation and micro-dissection in glycerine jelly.