. The cell; outlines of general anatomy and physiology. Cells; Anatomy; Physiology; Cells; Anatomy; Physiology. 46 THE CELL retained, the nucleus appears as a compact globular mass of nuclein; this is the case in the sperm, elements of Ascaris megalocephxla (Pig- 22), which, when immature, are shaped like fairly large, round cells, and when mature assume the form of a thimble. Having examined this simple condition of the nucleus, as it occurs in sperm-cells, and where it is composed almost entirely Fig. 22. â Sperm-cell of of active nuclear substances, being nearly â r, , f ââ r. free from the
. The cell; outlines of general anatomy and physiology. Cells; Anatomy; Physiology; Cells; Anatomy; Physiology. 46 THE CELL retained, the nucleus appears as a compact globular mass of nuclein; this is the case in the sperm, elements of Ascaris megalocephxla (Pig- 22), which, when immature, are shaped like fairly large, round cells, and when mature assume the form of a thimble. Having examined this simple condition of the nucleus, as it occurs in sperm-cells, and where it is composed almost entirely Fig. 22. â Sperm-cell of of active nuclear substances, being nearly â r, , f ââ r. free from the admixture ot other sub- Van Beneden ; from O. ^^^^ Hertwig's Emhryoiogy, Fig. stances, "WO may now proceed to examine 21): fc nucleus; b base of ^^^^^^ nuclear forms. In these we see that cone, by whicn it attaches itself to the egg; /shining the chief cause foT the variety in form, which substance resembling fat. ^^^ heen observed in plant and animal cells, is the fact, that the active nuclear substances evince a great inclination to taJce up liquid, with the substances dissolved in it, and to store it up, generally to such an extent, that the whole nucleus acquires the ap- pearance of a bladder enclosed in protoplasm. Thus in the nucleus, a process takes place similar to that which occurs in protoplasm, where the cell-sap becomes collected in vacuoles or large sap-cavities. This circumstance bears the same significance in either case. These vacuoles are concerned in the metabolism both of the cell and of the nucleus, for they contain in solution nutrient materials, which can be easily taken up by the active substances, in consequence of the great superficial de- velopment of the vacuoles. This process of sap absorption may be directly observed when, after fertilisatioii has taken place, the nucleus of the sperma- tozoon, in performance of its function, enters the egg-cell. In many cases it begins to swell up gradually, until it becomes ten to twenty times as large a
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