Germ-cells sentence example

  • According to Wulfert [60] the primitive germ-cells of Gonothyraea can be distinguished soon after the fixation of the planula, appearing amongst the interstitial cells of the ectoderm.
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  • When ripe, the germ-cells are dehisced directly to the exterior.
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  • If the germ-cells are undifferentiated, the offspring may arise from many cells or from a single cell; the first type is (4) germinal budding, the second is (5) sporogony.
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  • In individuals either of the male or female sex, germ-cells which are quite undifferentiated and neutral in character, become amoeboid, and wander into the endoderm.
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  • Petrunkevich (1901-1903), the second polar nucleus uniting with one daughter-nucleus of the first polar body gives rise to the germ-cells of the parthenogenetically-produced male.
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  • No doubt can be entertained that the greater part of the inner layer corresponds to the mesoderm of more ordinary embryos, for the coelomic pouches, the germ-cells, the musculature and the vascular system all arise from it.
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  • In the cockroach embryo, before the segmentation of the germ-band has begun, the primitive germ-cells can be recognized at the hinder end of the mesoderm, from whose ordinary cells they can be distinguished by their larger size.
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  • Ritter (1890) have since observed a similar early origin for the germ-cells in the midge Chironomus and in the Aphidae.
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  • Then we have Beard's " germ-cell " hypothesis, in which he holds that many of the germ-cells in the growing embryo fail to reach their proper position - the generative areas - and settle down and become quiescent in some somatic tissue of the embryo.
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  • The cilia are lost, the eye-spots disappear, the digestive sac vanishes and the larva becomes a sac or "sporocyst" full of germ-cells.
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  • By a series of changes similar to those by which the primary larva arose from a segmented egg, so do these secondary larvae or "rediae" arise from the germ-cells or germ-balls within the sporocyst.
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  • The question, however, is complicated by the uncertain nature of the germ-cells in the sporocysts and rediae.
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  • In germinal reproduction the proliferating cells may be undif f erentiated, so-called primitive germ-cells, or they may be differentiated as sexual cells, male or female, i.e.
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  • Among the most important structures produced in repeated series are the reproductive cells; and Pearson points out that if the variability of animals or of plants be supposed to depend upon that of the germ-cells from which they arise, then the correlation between brothers in the array produced by the same parents will give a measure of the correlation between the parental germ-cells, the determination requiring, of course, the same precautions to avoid the effects of differentiation as are necessary in the study of other repeated organs.
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