Archive image from page 220 of Cytology, with special reference to. Cytology, with special reference to the metazoan nucleus cytologywithspec00agar_0 Year: 1920 VII MITOSIS IN PROTISTA 205 the chromatin granules in linear series had the same function as postu- lated for the chromosomes of a Metazoan mitosis, namely, to effect their accurate division and partition among the daughter nuclei. In some Protista very well-developed mitosis, closely resembling that in the Metazoa and Metaphyta, is found (Fig. 85). In the Coccidian, Aggregata eberthi (Dobell and Jameson, 1915) the nuclei of the prim
Archive image from page 220 of Cytology, with special reference to. Cytology, with special reference to the metazoan nucleus cytologywithspec00agar_0 Year: 1920 VII MITOSIS IN PROTISTA 205 the chromatin granules in linear series had the same function as postu- lated for the chromosomes of a Metazoan mitosis, namely, to effect their accurate division and partition among the daughter nuclei. In some Protista very well-developed mitosis, closely resembling that in the Metazoa and Metaphyta, is found (Fig. 85). In the Coccidian, Aggregata eberthi (Dobell and Jameson, 1915) the nuclei of the primary gametocytes (3 and ? ) show in mitosis six chromosomes of very different sizes (labelled, from largest to smallest, a-f in Fig. 86). The macrogametocyte is transformed into the macro- gamete without any reduction of chromosomes, the macrogamete having therefore the same series of six chromosomes. The pri- mary microgametocyte nucleus undergoes repeated division to form the microgamete nuclei, the same series of six chromosomes appearing throughout, though becoming greatly reduced in size. Both gametes have therefore, like the gametocytes, six chromo- somes. Syngamy results in a zygote with twelve chromosomes which can be sorted out into pairs as in a typical Metazoan diploid nucleus. In the metaphase of the first division Of the Zygote nUCleUS the (After Brasil, Arch. Zool. Exp. Gen., 1905.) A, B, pro- J ° phase ; C, anaphase. homologous chromosomes become united into bivalents, the constituents separating at anaphase. This division therefore is a reduction division and the daughter nuclei have only six chromosomes. This number is retained throughout all the subsequent nuclear divisions of the life cycle, which include spore formation, the asexual multiplication of the schizont, and the gametocyte divisions again. Thus in this animal the relation be- tween the duration of the haploid and diploid phases is the reverse of what obtains in the Metazoa, the nuclei being haploid
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