. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . dle, at which point the plasma of the two individuals remainsin continuity without interference by the forming skeleton. As the newlyforming skeletons are completed, the apical pore of the posterior schizontis set under the anterior shelf or list of the distal end of the girdle at themargin of the ventral plate of the anterior schizont. The posterior list ofthe girdle is not formed at this point, and the apical horn as it passesposteriorly li
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . dle, at which point the plasma of the two individuals remainsin continuity without interference by the forming skeleton. As the newlyforming skeletons are completed, the apical pore of the posterior schizontis set under the anterior shelf or list of the distal end of the girdle at themargin of the ventral plate of the anterior schizont. The posterior list ofthe girdle is not formed at this point, and the apical horn as it passesposteriorly lies in a channel or depression on the ventral face of the mid-body along the right margin of the ventral plate. Kofoid designates the Peridiniacese 71 place of junction on the anterior schizont the attachment area, and thedepression the chain channel (consult fig. 53). Lohmann observed heteromorphic chains of Ceratium tripos, and Kofoidhas given some interesting information on two cases of mutation, one ofCeratium tripos to G. calif or niense, and the other of 0. Ostenfeldii toC. californiense. In the rare instances in which mutations occur, Kofoid. Fig. 51. Peridinium anylicuiii G. S. West. A, ventral view; B, dorsal view; C, apical view;D, antapical view; E, thin-walled cyst within old wall; F, escaped cyst; G and H,division of escaped cyst; /, escape of an elongated cyst from old wall; J, escape ofnaked motile individual from cyst; A and L, divisions of naked motile state. All x fig. C: 1—3, apical plates; 1—7, precingular plates; 1, anterior intercalary plate. finds very abrupt changes involving a whole complex of fundamentalcharacters, so that in one, or at most in two generations of asexually-produced individuals the descendants differ profoundly from the ancestraltype. The fact that the mutating chains have been seen so rarely incomparison with the vast numbers of normal chains which have been 72 Peridinieae observed, coincides with observations on mutati
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