The history of creation, or, The development of the earth and its inhabitants by the action of natural causes : a popular exposition of the doctrine of evolution in general, and of that of Darwin, Goethe and Lamarck in particular . of the albuminous combinationof carbon, of which the egg essentially consists. Theseminute individual differences of all eggs, which depend uponindirect or potential adaptation (and especially upon thelaw of individual adaptation), are indeed not directly per-ceptible to the exceedingly imperfect senses of man, but arecognisable through indirect means, as the primar
The history of creation, or, The development of the earth and its inhabitants by the action of natural causes : a popular exposition of the doctrine of evolution in general, and of that of Darwin, Goethe and Lamarck in particular . of the albuminous combinationof carbon, of which the egg essentially consists. Theseminute individual differences of all eggs, which depend uponindirect or potential adaptation (and especially upon thelaw of individual adaptation), are indeed not directly per-ceptible to the exceedingly imperfect senses of man, but arecognisable through indirect means, as the primary causes ofthe difference of all individuals. The human egg is, like that of all other mammals, asmall globular bladder, which contains all the constituentparts of a simple organic cell (Fig. 5). The most essential Fig. 5.—^The human egg a hundred times a. The kernel speck, or nucleolus (theso-called germinal spot of the egg), h. Kernel,or nucleus (the so-called germinal vesicle of theegg), c. Cell-substance, or protoplasm (so-calledyolk of the egg), d. Cell-membrane (the yolk-membrane of the egg; in mammals, on accountof its transparency, called zona pellucida). Theefjofs of other mammals are of the same -00 parts of it are the mucous cell-substance, or the protoplasma(c), which in an egg is called the yolk, and the cell-kernel,or nucleus (b), surrounded by it, which is here called by thespecial name of the germinal vesicle. The latter is a deli-cate, clear, glassy globule of albumen, of about 1-600th part ofan inch in diameter, and surrounds a still smaller, sharply-marked, rounded granule (a), the kernel-speck, or the nucle-olus of the cell (in the egg it is called the germinal spot).The outside of the globular egg-cell of a mammal is sur-rounded by a thick pellucid membrane, the cell-membrane 29^ THE HISTOPvY OF CEEATION. or yolk-membrane, which here bears the special name ofzona pellucida (d). The eggs of many lower animals(for example of many Medusse)
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Keywords: ., bookauthorlankestererayedwinray, bookcentury1800, bookdecade1880
