Archive image from page 222 of Cytology, with special reference to. Cytology, with special reference to the metazoan nucleus cytologywithspec00agar_0 Year: 1920 vii CHROMIDIA IN PROTISTA 207 Another example of multiplication of nuclei by chromidia formation alternating with multiplication by mitotic division, though attended by more complications, is afforded by Arcella (Fig. 88), the life history of Fig. 87. Stages in the formation of macrogametes in Mastigella vitrea. (After Goldschmidt, , 1907.) A, macrogametocyte nucleus surrounded by extruded chromidia. B, a later stage. As the
Archive image from page 222 of Cytology, with special reference to. Cytology, with special reference to the metazoan nucleus cytologywithspec00agar_0 Year: 1920 vii CHROMIDIA IN PROTISTA 207 Another example of multiplication of nuclei by chromidia formation alternating with multiplication by mitotic division, though attended by more complications, is afforded by Arcella (Fig. 88), the life history of Fig. 87. Stages in the formation of macrogametes in Mastigella vitrea. (After Goldschmidt, , 1907.) A, macrogametocyte nucleus surrounded by extruded chromidia. B, a later stage. As the chromidia get further away from the nucleus they are formed into the macrogamete nuclei. C, gametocyte full of macro- gametes. Some are undergoing the (? reduction) division. D, four of the macrogametes from C on a larger scale. Three are in mitosis, and the fourth has completed the mitosis and contains the mature gamete nucleus and the polar body-like ' reduction body.' ch, chromidia ; tn, macrogamete nuclei; r, ' reduction body.' which has been studied by many workers. The essential features from our present point of view are as follows. At the beginning of the asexual cycle the young Arcella consists of a minute uninucleated cell. Soon the nucleus divides into two, by mitosis. At about the same time a great number of chromidia are emitted from the nuclei. These become
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