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actual already Anat animal development appear become Boveri cells characters conclusion conjugation degeneration destined determination of sex differentiation Dinophilus dioecious drone-cells drone-eggs drones Dzierzon's embryo embryology existence facts female-eggs fertilisation final division form of sperm form of spermatozoon formation functional gametes give rise hairlike hermaphroditism individual influence instances isogamy Jena kinds of spermatozoa latter life-cycle male gamete male-eggs Maupas Metazoa Meves mitoses number of females number of primary occurrence offspring oocytes oocytes and spermatocytes oogenesis oogonia origin Paludina parthenogenesis period phenomena Phylloxera polar bodies present writing primary germ primary germ-cells primitive germ-cell probably production queen-bee Raja batis reduction of chromosomes regulation of sex researches result ripening Rotifera Sacculina second form sex in animal sexual sexually differentiated Siebold smooth skate sorts of eggs sorts of gametes species sperm spermato spermatocytes spermatogenesis spermatogonia spermatozoa Strasburger supposed synapsis Ueber unlike gametes Valette St Weismann wormlike spermatozoa writer Zool
Page 763 - Any interference with, or alteration of, the determination of sex is absolutely beyond human power. To hope ever to influence or modify its manifestations would be not less futile and vain than to imagine it possible for man to breathe the breath of life into inanimate matter.
Page 727 - Memoire sur la ponte de 1'abeille reine et la theorie de Dzierzon.
Page 747 - ... it is in the highest degree improbable that the two series of phenomena can have been independently evolved ; and whatever the synapsis may eventually turn out to be, it is evidently a cellular metamorphosis of a profoundly fundamental character, which would appear to have been acquired before the animal and vegetable ancestry went apart, and to have existed ever since.
Page 747 - Little attention was paid to this work, as for some time synapsis was thought to be an artifact. Moore firmly believed, however, that this unilateral massing of the chromatin was natural and said that " whatever the synapsis may eventually turn out to be it is evidently a cellular metamorphosis of profoundly fundamental character." He, as well as many later investigators, found that in many cases the chromosomes emerged from synapsis in the reduced number and frequently longitudinally split. From...
Page 732 - ... be determined prior to the final phenomena of the reduction and of the ripening, for these latter would not appear to possess any influence on the size of the egg itself. In other words, the size of the egg and its prospective destination, male or female, must be "arranged" prior to the ripening and reduction, ie , prior to the two final mitoses.
Page 732 - The small eggs here are destined to produce males, the large ones females. As the size of the egg will naturally be attained during the oogenesis, it would seem to follow, that here the destination of the oogonium must be determined prior to the final phenomena of the...
Page 717 - This was found to be the case: the germinal discs of segmenting eggs of the smooth skate are of two sizes 1).
Page 714 - Where the parthenogenetic development of eggs of the one sex, or of the other, has been initiated, there is an undoubted tendency for such eggs to become in the long run incapable of fertilisation.