. An atlas of the fertilization and karyokinesis of the ovum. Ovum; Fertilization (Biology); Meiosis; Embryology -- Echinodermata. Fig. XII. Fig. XII. — Conjugation of the nuclei. Extension and division of the sperm-aster (looo diameters). A. The two nuclei here lie in contact, the sperm-nucleus considerably enlarged and showing a reticular structure. The sperm-aster has enormously increased; its central mass extends like a cap far down upon the egg-nucleus, and its rays traverse nearly an entire hemisphere of the egg. (Phototype iS.) B. The sperm-aster has divided into two. The sperm-nucleus
. An atlas of the fertilization and karyokinesis of the ovum. Ovum; Fertilization (Biology); Meiosis; Embryology -- Echinodermata. Fig. XII. Fig. XII. — Conjugation of the nuclei. Extension and division of the sperm-aster (looo diameters). A. The two nuclei here lie in contact, the sperm-nucleus considerably enlarged and showing a reticular structure. The sperm-aster has enormously increased; its central mass extends like a cap far down upon the egg-nucleus, and its rays traverse nearly an entire hemisphere of the egg. (Phototype iS.) B. The sperm-aster has divided into two. The sperm-nucleus is flattened against the egg-nucleus forming a lens-shaped bodv. (Phototype 19.) This fact indicates that the rays are really fibres, and not, as some recent authors have maintained, merely the optical sections of thin plates or lamella' in a radially arranged alveolar structure. In the European sea-urchin. Echinus niicrotubcrculatus, Boveri describes both the germ-nuclei as containing, at this period, nine elongated chromosomes. In Toxopneustcs, the chromosomes cannot be distinguished until a much later period, and both nuclei consist of an irregular reticulum of chromatin. Pl.\te V. Phototype 20. Nuclei fusing. Sperni-mccleus en face. A stage just later than the last viewed from the side of the sperm-nucleus. The sperm-nucleus appears as a dark irregular mass at the left upper side, its boundary having been nearly lost. The chromatin-granules of the egg-nucleus are distinctly Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Wilson, Edmund B. (Edmund Beecher), 1856-1939; Leaming, Edward, 1861-1916. New York, London, Pub. for the Columbia university press by Macmillan and co.
Size: 1851px × 1350px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorwilsoned, bookcentury1800, bookdecade1890, bookyear1895
