. Carnegie Institution of Washington publication. Hyhridizalion of Echinoids. 29 sperm nucleus are involved in division, and that of a sperm carrying but one heterochromosome. The expected number of chromosomes in this case would thus be 19 + 18 = 37; these have all split in division, which would give a total of 74. The number shown in the figure is 80, of which some are evidently fragments. One of the V's has been cut in sectioning. I am unable to designate its parts. Chromosomes in Cidaris Eggs Cross-Activated by Tripneustes Sperm. Cidaris 9 X Tripneustes cf. Figures 18 to 25. In general, th
. Carnegie Institution of Washington publication. Hyhridizalion of Echinoids. 29 sperm nucleus are involved in division, and that of a sperm carrying but one heterochromosome. The expected number of chromosomes in this case would thus be 19 + 18 = 37; these have all split in division, which would give a total of 74. The number shown in the figure is 80, of which some are evidently fragments. One of the V's has been cut in sectioning. I am unable to designate its parts. Chromosomes in Cidaris Eggs Cross-Activated by Tripneustes Sperm. Cidaris 9 X Tripneustes cf. Figures 18 to 25. In general, the division figures of this cross are more regular than those of the Cidaris-Lytechinus cross. There are some lagging chromosomes, but these do not form so striking a feature as in the preceding cross. Some of the sections show the heterochromosomes especially well. In figure 18, for example, 3 V-shaped and 1 hook- like chromosome are present; in figure 19, 3 V-shaped chromosomes tii%\\\ il\ M'^h . i\ I I \ ct b. / ' ^- • 15 5/ Fig. 14, a and b, Cidaris 9 X Lylcch- imi-sd^. Three heterochromo- Fig. 15, a and b, Cidaris 9 X Lytechinusd'. The V- somes. Lagging chromo- shaped form of the heterotypic chromo- somes at center, 27?-35? somes shows clearly 29-28. were present in the egg, but no hook-shaped chromosome was present. These two illustrations represent the two classes of eggs that were present in these cultures. ^ In figures 20, b and c, 3 V's; in figures 21, a and 6, 3 V's and a hook; in figures 22, a and b, 3 V's; in figures 23, a and 6, 3 V's and a hook. The sections from which figures 24, a and b, were drawn are of more than usual interest. Most of the chromosomes appearing in b are longitudinal sections of the chro- mosomes shown in a, as indicated both by position and width of the chromosomes. The third section of this spindle (not shown in the illustrations) contains a much involved mass of chromosomes, v/hich. Please note that these images are extracted from scanned
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Keywords: ., bookauthorcarnegie, bookcentury1900, bookdecade1920, bookyear1922
