. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . lankton-organism has recently been carefullyexamined by Kofoid (07 A), who hasshown that it is merely a member ofthe Gymnodiniacea with a permanentcolonial organization. There are two,four, or eight transverse groves, eachwith its flagellum and each correspondingto the equatorial region of a single in-dividual. The longitudinal furrows areall continuous, but there are as manylongitudinal flagella as there are trans-verse flagella. The hindmos
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . lankton-organism has recently been carefullyexamined by Kofoid (07 A), who hasshown that it is merely a member ofthe Gymnodiniacea with a permanentcolonial organization. There are two,four, or eight transverse groves, eachwith its flagellum and each correspondingto the equatorial region of a single in-dividual. The longitudinal furrows areall continuous, but there are as manylongitudinal flagella as there are trans-verse flagella. The hindmost flagellum ishowever somewhat longer and acts as thepropelling organ. Kofoid also found thatthe nuclear division was not alwayscoincident with, but often lagged behindthe multiplication of superficial structuressuch as furrows, flagella, etc. Polykrikosis therefore a permanent colonial memberof the GymnodiniaceaB consisting of two,four, or eight individuals which areonly incompletely separated. Temporarycolonies occur in Spirodinium geminatumand in the active Gt/>iinodinium-sta,ges of some of the Peridiniaceae (videfig. 51 K and L). ... -Up. flagella, and flagellar pores in a some-what contracted individual. Const.,constriction between individuals ofcolony; /./., longitudinal flagellum;, pore of longitudinal flagellum ;n., nuclei; , transverse flagellum ; Pyrocystacese 55 In the peripheral zone of the protoplast, Polykrikos tic/nvartzii Blitschliand Pouchetia antiata Dogiel are provided with nematocysts. It isby no means easy to explain how these structures are functional in uni-cellular organisms of such a type. It is easy to state that they play a partin nutrition, but there is no evidence to show that the nutrition of theseorganisms is other than saprophytic. Possibly they act purely as protectivestructures. The organism known for a long time as Pyrocystis limula (fig. 40 B and C)has quite recently been transferred by Klebs (12) to the Gymnodini
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