If we suppose, and this is not contradicted by observation, that the Richtungskörper is either only the metamorphosed membrane of the germinal vesicle with parts of the yolk, or part of the yolk alone, and assume that in Oellacher's observations only the membrane and not the contents were extruded from the egg, it would be possible to frame a consistent account of the behaviour of the germinal vesicle throughout the animal kingdom, which may be stated in the following way. The germinal vesicle usually before, but sometimes immediately after impregnation undergoes atrophy and its _contents_ become indistinguishable from the remainder of the egg. In those cases in which its membrane is very thick and resistent, _e.g._ Osseous and Elasmobranch Fishes, Birds, etc., this may be incapable of complete resorption, and be extruded bodily from the egg. In the case of most ova, it is completely absorbed, though at a subsequent period it may be extruded from the egg as the Richtungskörper. In all cases the contents of the germinal vesicle remain in the ovum. In some cases the germinal vesicle is stated to persist and to undergo division during the process of segmentation; but the observations on this point stand in need of confirmation. My investigations shew that the germinal vesicle atrophies in the Skate before impregnation, and in this respect accord with very many recent observations. Of these the following may be mentioned. (1) Oellacher (Bird, Osseous Fish). (2) Götte (Bombinator igneus). (3) Kupffer (Ascidia canina). (4) Strasburger (Phallusia mamillata). (5) Kleinenberg (Hydra). (6) Metschnikoff (Geryonia, Polyzenia leucostyla, Epibulia aurantiaca, and other Hydrozoa). This list is sufficient to shew that the disappearance of the germinal vesicle before impregnation is very common, and I am unacquainted with any observations tending to shew that its disappearance is due to impregnation.