. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 308 C. E. MCCLUNG. instead of univalent. The chromatids composing this multiple chromosome l are amongst the largest in the cell and are easily distinguishable. During the anaphase it is seen that the multiple chromosome exhibits the so-called heterotypical form of division, and the figure produced is exactly the same as that resulting from the division of the tetrads in the first spermatocyte. In reality we have here a tetrad that is in every respect the same as those in the succeeding generation. A precocious synapsis of c
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 308 C. E. MCCLUNG. instead of univalent. The chromatids composing this multiple chromosome l are amongst the largest in the cell and are easily distinguishable. During the anaphase it is seen that the multiple chromosome exhibits the so-called heterotypical form of division, and the figure produced is exactly the same as that resulting from the division of the tetrads in the first spermatocyte. In reality we have here a tetrad that is in every respect the same as those in the succeeding generation. A precocious synapsis of chromo- somes in the spermatogonia is responsible for the unusual type of division in this generation of cells. There can be no mistake about the nature °f thi8 multiple chromosome, for the line of fusion between the two chromosomes is clearly marked, and the mantle fibers of the FIG. 2. The hexad metaphase attach at the center of the U- multiple chromosome of shaped element. In the anaphase the con- Hesperotetti* in the first tragt between this chromosome and the spermatocyte prophase. The accessory chromo- others is very marked, for the daughter some "; is homo- chromosomes of the latter ascend to the geneousand the ordinary poles as strajght rods with the fibers at the chromosomes granular, .. ends, while the former are U-shaped and as is usually the case for these elements at this have the fibers annectent at the center, or stage. where the chromatids are joined .together. The early prophase of the first spermatocyte shows this bivalent element among the others, which have by this time also become bivalent, but it may still be distinguished by its greater leneth. When the chromosomes commence to shorten and con- o dense the accessory chromosome attaches itself to one end of the large bivalent element, thus forming a trivalent chromosome. As thus constituted the multiple chromosome is much longer than any of the others, and clearly shows the limits of the three
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
