The Maturation of the Egg of the Mouse Volume 142

The Maturation of the Egg of the Mouse Volume 142

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1911 Excerpt: ...the difficulty of counting is usually increased. However, knowing the structure of the chromosomes, it has been possible in many cases to be stlzCoi quite certain that the number is 20 (see table 2, p. 14). In figs. 23a and 236 there are onlv 19 chromosomes, one probably having been lost in cutting. Figs. 24a and 246 exhibit together 20, one having been so cut that a half of it lies in each section. The two sections (24a and 24b) contain, respectively, 8.5 and 11.5 chromosomes. Polar views of the "equatorial plate" are usually the most satisfactory ones for counting. In fig. 20, a polar view, there are clearly 20 chromosomes; one of these (x), seen in face view, corresponds to fig. /, n. In figs. 28a and 286 (an anaphase) the number can not be determined with perfect accuracy, because the long axes of the daughter chromosomes are perpendicular to the plane of the section. Two of the larger chromosomes x and x') may well be double; if so, the number in this case also is 20. In the division of the chromosomes, the two elements of each mother chromosome separate and then migrate to the opposite poles of the spindle. Figs. 28a and 286 (plate 5) are polar views of the two daughter plates at a stage of migration corresponding to that of fig. 16, and are drawn from a non-seminated egg. In fig. 29, which represents a slightly later stage than fig. 28, the individual chromosomes are no longer distinguishable. They seem quickly to lose their identity and merge into a single disk-shaped mass (fig. 30), as in the case of the first spindle. 3. ACHROMATIN PARTS OF SECOND MATURATION SPINDLE. The interzonal filaments left in the egg after the first polar cell is cut off persist for a while along with the chromatin mass. About the time when the chromatin breaks up...
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Product details

  • Paperback | 34 pages
  • 189 x 246 x 2mm | 82g
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1130154068
  • 9781130154061