“The development of the Vertebrate proceeds from an axis upward, in two layers, which coalesce at the edges, and also downward, in two layers, which likewise coalesce at the edges. Thus two main tubes are formed, one above the other. During the formation of these, the embryo separates into strata, so that the two main tubes are composed of subordinate tubes which enclose each other as fundamental organs, and are capable of developing into all the organs.” TwoDevelopmentCapableFundamentalsEdgesDevelopingOrgansLayersFormationTubesSubordinatesAxesEmbryosVertebrates Author:Karl Ernst von Baer
“The distinguishing of the strata, or layers, in the embryonic membrane was a turning-point in the study of the history of evolution, and placed later researches in their proper light. A division of the (disc-shaped) embryo into an animal and a plastic part first takes place. In the lower part (the plastic or vegetative layer) are a serous and a vascular layer, each of peculiar organization. In the upper part also (the animal or serous germ-layer) two layers are clearly distinguishable, a flesh-layer and a skin-layer. (1828)” FirstsTwoLightAnimalStudyEvolutionResearchSkinsOrganizationFleshDivisionPeculiarLayersPlasticGermsTurning PointsEmbryosDiscsMembranes Author:Karl Ernst von Baer
