. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . cal Volvocine kind and contains a pyrenoid. Apigment-spot is present in some forms but absent in others. 1 Pascher has attempted to overcome this difficulty by splitting up the genera Ulothrix andStigeocloniuin (= Myxonema) on grounds which appear to be inadequate. PolyblepJi <t i • it laceae 165 Multiplication takes place by longitudinal fission, in some forms com-mencing at the anterior and in others at the posterior extremity. Resting-e
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . cal Volvocine kind and contains a pyrenoid. Apigment-spot is present in some forms but absent in others. 1 Pascher has attempted to overcome this difficulty by splitting up the genera Ulothrix andStigeocloniuin (= Myxonema) on grounds which appear to be inadequate. PolyblepJi <t i • it laceae 165 Multiplication takes place by longitudinal fission, in some forms com-mencing at the anterior and in others at the posterior extremity. Resting-eells are formed by the direct encystment of the motile individuals. Gametesof a more or less isogamous character occur in DunaUella (Teodoresco, 05),and they fuse in pairs to form zygotes. The most primitive genus of the family is Polyblepha/rides, in which the body of thecell is conical with a broad anterior end to which are attached from six to eight cilia. InPyntiitiiiioinix, which possesses only four cilia, the cell-body is also more or less conical,and is four-lohed in the anterior region. Chloraster, which is furnished with five cilia, H Fig. 95. A—E, DunaUella salina (Duual) Teodoresco ; A and B, normal form of zoogouidia( — vegetative cells) ; C and D, stages in division, in D the second cilium making itsappearance; E, single cell showing detailed structure. F—/, Pyramimonas delicatulituGriffiths ; F, vegetative cell; G, beginning of longitudinal fission, the pyrenoid havingdivided and 8 cilia developed ; H, peculiar blistering and disintegration of cell on treatmentwith 4 per cent, formalin, showing swelling of cilia at their extremities; I, anterior axialview of H at an earlier stage in disintegration showing lobed chloroplast. c, cilia ;», nucleus; pc, posterior excavation of chloroplast; pt, protoplasmic membrane; py,pyrenoid ; s, minute grains of starch; /, plasmatic thread from nucleus to base of — D, after Teodoresco, x 1000 ; E, afte
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Keywords: ., bookcentury1900, bookdecade1910, bookpublishercambridgeengtheuni
