. The development of the human body : a manual of human embryology. Embryology; Embryo, Non-Mammalian. 15 SPEEMATOGENESIS filament grows out and soon projects beyond the limits of the cyto- plasm (Fig. g, A). The other centrosome becomes a rod-shaped structure which applies itself closely to the posterior pole of the nucleus, becoming the anterior nodule, while the lower one, from which the filament arises, becomes at first pyramidal in shape (Fig. 9, B) and later separates into a rod-like portion to which the filament is attached and a ring, through which the filament passes (Fig. 9, C). The
. The development of the human body : a manual of human embryology. Embryology; Embryo, Non-Mammalian. 15 SPEEMATOGENESIS filament grows out and soon projects beyond the limits of the cyto- plasm (Fig. g, A). The other centrosome becomes a rod-shaped structure which applies itself closely to the posterior pole of the nucleus, becoming the anterior nodule, while the lower one, from which the filament arises, becomes at first pyramidal in shape (Fig. 9, B) and later separates into a rod-like portion to which the filament is attached and a ring, through which the filament passes (Fig. 9, C). The rod-like portion becomes the posterior nodule,. ABC Fig. g.—Stages in the Transformation of a Spermatid into a Spermatozoon.—(After Meves.) and the ring separates from it to form the annulus (Fig. g,D). The nucleus becomes the head of the spermatozoon, the cytoplasm sur- rounding it becoming reduced to an exceedingly delicate layer, so that the head is composed almost entirely of nuclear substance, if the head-cap be left out of consideration. The spiral filament of the middle-piece is, however, a derivative of the cytoplasm and according to some authors this portion of the spermatid also fur- nishes the material for the sheath of the axial filament, though this has been denied (Meves), the sheath being regarded as a differ- entiation of the axial filament. Each spermatozoon is, then, one of four equivalent cells, produced by two successive divisions of a primary spermatocyte and containing one-half the number of chromo- somes characteristic for the 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 McMurrich, J. Playfair (James Playfair), 1859-1939. Philadelphia : P. Blakiston's son & co.
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