. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . Fig. 87. Two small pennate diatoms. A—C, Navicula muticopsis Van Heurck. D, Naviculaglobiceps Greg. All x 1500. A is a girdle view, B—D are valve views. The classification put forward by Forti (12) is based primarily upon thefact that some diatoms are capable of spontaneous movements, whereas othersare not. Forti accepts O. Miillers interpretation of these spontaneous move-ments as being due entirely to protoplasmic currents circulating in th

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. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . Fig. 87. Two small pennate diatoms. A—C, Navicula muticopsis Van Heurck. D, Naviculaglobiceps Greg. All x 1500. A is a girdle view, B—D are valve views. The classification put forward by Forti (12) is based primarily upon thefact that some diatoms are capable of spontaneous movements, whereas othersare not. Forti accepts O. Miillers interpretation of these spontaneous move-ments as being due entirely to protoplasmic currents circulating in the raphe,and therefore the primary division separates all those diatoms which possessa raphe (whether perfectly or imperfectly developed) from those which donot. One improvement upon Schiitts arrangement is the more definiteseparation of the naviculoid diatoms from the Nitzschie?e. The scheme isbriefly as follows: I. Immobiles. Diatoms incapable of spontaneous movement. Conjugation unknown(perhaps non-existent) or possibly by the fusion of microspores. A. Valves usually circular, more rarely elliptic or reniform. Includes Melosireo?,Coscinodisc

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