. An atlas of the fertilization and karyokinesis of the ovum. Ovum; Fertilization (Biology); Meiosis; Embryology -- Echinodermata. Fi.:. III. Fig. III. — History of the germ-nuclei in the KYi^i' Ascaris megalocephaUi (after Boveri), highly magnified. A. Egg immediately after the formation of the second polar body, PB; E, the egg-nucleus, consisting of two branching chromosomes; S, the sperm-nucleus derived from the head of a spermatozoon that has entered the egg. B. Following stage, in which the egg-nucleus (E) and sperm-nucleus (S) have assumed the same size and structure. C. Later st
. An atlas of the fertilization and karyokinesis of the ovum. Ovum; Fertilization (Biology); Meiosis; Embryology -- Echinodermata. Fi.:. III. Fig. III. — History of the germ-nuclei in the KYi^i' Ascaris megalocephaUi (after Boveri), highly magnified. A. Egg immediately after the formation of the second polar body, PB; E, the egg-nucleus, consisting of two branching chromosomes; S, the sperm-nucleus derived from the head of a spermatozoon that has entered the egg. B. Following stage, in which the egg-nucleus (E) and sperm-nucleus (S) have assumed the same size and structure. C. Later stage, in which the substance of each germ-nucleus has become transformed into two chromosomes, —, each sex has contributed two of these bodies, exactly similar in form and size. On either side, at A, is an attraction-sphere or archoplasm-sphere, each containing a single centrosome. These were originally supposed by \ an Beneden to be derived one from each sex. Boveri showed that the two arise by the division of one sphere, which is developed under the influence of a centrosome, derived from the spermato- zoon alone. D. The karyokinetic figure forming for the first cleavage. The archoplasm-spheres have given rise to two asters (A) between which a spindle (S) is forming. The chromosomes (C) are splitting lengthsvisc, the two halves being destined respectively for the two daughter-cells. a tolerably definite chemical composed of nucleic acid (a complex organic acid rich in phosphorus) and albumin. And thus we reach the remarkable conclusion that inheritance may, perhaps, be effected by the physical transmission of a particular chemical compound from parent to offspring. Structure of the Resting-cell. — It is now necessary to consider briefly the structure of the resting-cell as an introduction to the subject of cell-division, which, in turn, leads us to another aspect of fertilization. In the resting-cell (Text-fig. V. A) the protoplasm of the cell-body, or cytoplasm, con
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Keywords: ., bookauthorwilsoned, bookcentury1800, bookdecade1890, bookyear1895
