. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . The cells are globose, and thebell-shaped chloroplast may possess more than one pyrenoid. In Pleodorina(fig. 106) there is a differentiation into smaller, purely vegetative (somatic)cells, which occupy the anterior region of the coenobium, and larger reproduc-tive (or gonidial) cells which are alone capable of division. This differentiationis possibly constant in Pleodorina californica Shaw (94), especially in viewof the observations of Chatt
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . The cells are globose, and thebell-shaped chloroplast may possess more than one pyrenoid. In Pleodorina(fig. 106) there is a differentiation into smaller, purely vegetative (somatic)cells, which occupy the anterior region of the coenobium, and larger reproduc-tive (or gonidial) cells which are alone capable of division. This differentiationis possibly constant in Pleodorina californica Shaw (94), especially in viewof the observations of Chatton (11); but in P. illinoisensis Kofoid (98) thedifferentiation is not at all constant, and every intermediate state can beobserved between the coenobium as originally described and that of Eudorinaelegam1. In any case, the two forms are of great interest since they are linksbetween Eudorina and K Fig. 104. A—H, Pandorina Morum (Mull.) Bory; A, normal colony; B, daughter-colonieswithin the swollen mother-cell-wall, x 475 ; C—H, gametes (g), formation of zygospore (z),and its development (after Pringsheim). K, Slephanosphsera pluvialis Cohn, ordinaryvegetative colony (after Hieronymus, x 320). Platydorina, described by Kofoid (99) from the United States, is one ofthe most curious of the Volvocese, the coenobium consisting of a twisted plateof 16 or 32 cells, the enveloping jelly being produced posteriorly into 3 or 5 1 The author has examined large numbers of Pleodorinn illinoisensis from Yorkshire, thewest of Scotland, the west of Ireland, and Madras. The somatic cells may be entirely absent,or they may vary in number from 1 to 12 ; moreover, every gradation in size occurs between thereproductive and the somatic cells, and the latter are somatic or non-somatic according to thedegree of differentiation in size. In many specimens somatic and reproductive cells are indis-cri
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