. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . cribed by Dangeard (10) is very similar toPyramimonas, but is only furnished with two cilia. It is thus a natural connecting-linkbetween Pyramimonas and Dunaliella. The genera included in this family are : Polyblepharides Dangeard, 1887 ; ChlorasterEhrenberg, 1848 ; Pyramimonas Schwarda, 1850 ; Tetratoina Biitschli, 1887 ; DunaliellaTeodoresco, 1905; Stephanoptera Dangeard, 1910; Asteromonas Artari, 1913; Spermato-Korachikoff, 1913. 166 Volvo
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . cribed by Dangeard (10) is very similar toPyramimonas, but is only furnished with two cilia. It is thus a natural connecting-linkbetween Pyramimonas and Dunaliella. The genera included in this family are : Polyblepharides Dangeard, 1887 ; ChlorasterEhrenberg, 1848 ; Pyramimonas Schwarda, 1850 ; Tetratoina Biitschli, 1887 ; DunaliellaTeodoresco, 1905; Stephanoptera Dangeard, 1910; Asteromonas Artari, 1913; Spermato-Korachikoff, 1913. 166 Volvocineas Family Sphaerellacese. Although but recently proposed (Schmidle, 03) and including only twogenera, the unicellular Spli&rella (= H&matococcus) and the colonial Stepha-nosph&ra, this family appears to be established upon a sound basis. Thenare two leading characters which distinguish the &ph»rellaceae from theVolvocacese: (1) the form of the protoplast with its outstanding branchedprocesses, and (2) the numerous contractile vacuoles. The presence of morethan one pyrenoid in the chloroplast is an important although not a dis-. Fig. 96. A—C, vegetative individuals (^zoogonidia) of Sphserella lacustri-t (Girod.) Wittr. A,surface view; B, optical section (after Schmidle); C, zoogonidiura from a snow-water-rnediurn (after Wollenweber). D—F, Splt&rella Dnebakensis (Wollenw.) G. S. , vegetative cell (zoogonidium) in optical section; E, gamete ; F, resting cell (all afterWollenweber). G and //, portions of individual cells of Stephanosphsera pluvialis Cohn, toshow general cytology; G, after Wollenweber; H, after Schmidle. All x about ;, nucleus; cv, contractile vacuole ; pi/, pyreuoid ; st, stigma ; v, vacuole. tinctive character. The peculiar nature of the protoplast, with its branchedprocesses, has resulted in a corresponding modification of the cell-wall, whichconsists of a firm outer membrane, extending around all the branched tipsof the processes, and
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