germ-layers

The comparability and fixity of the germ-layers in different animals were challenged by experimental evidence.

RECAPITULATION JANE OPPENHEIMER 1968

Like Reichert he held the visceral arches to be parts of the visceral plates, containing, however, elements from all three germ-layers -- the serous, mucous, and vessel layers.

Form and Function A Contribution to the History of Animal Morphology

Remak's conception of the relations of the three germ-layers to one another and to the body-cavity is well illustrated in Fig. 12.

Form and Function A Contribution to the History of Animal Morphology

The first of these differentiations in time is the formation of the germ-layers, which takes place by a splitting or separation of the blastoderm into a series of superimposed lamellæ.

Form and Function A Contribution to the History of Animal Morphology

It includes the 'directly inherited' structures, _i. e._, the structures which are directly predetermined in the structure of the germ-plasm, as, for instance, the first differentiation of the germ, segmentation, the formation of the germ-layers and the organ-rudiments, as well as the next stage of

Form and Function A Contribution to the History of Animal Morphology

They distinguished in the middle layer two quite distinct elements, the mesoblast proper, formed by the evagination of the walls of the archenteron, and the mesenchyme, formed by free cells budded off from the germ-layers.

Form and Function A Contribution to the History of Animal Morphology

Embryonic cells, which become singly detached from their epitheliar connections we consider to be something quite different from the germ-layers, and accordingly we call them by the special name of mesenchyme germs or primary cells of the mesenchyme.

Form and Function A Contribution to the History of Animal Morphology

Though Remak's germ-layer theory had thus principally a histological orientation, it laid down the main lines of the modern morphological treatment of the germ-layers.

Form and Function A Contribution to the History of Animal Morphology

It became apparent also that the parts first formed (germ-layers) were of primary importance for the establishing of homologies.

Form and Function A Contribution to the History of Animal Morphology

His generalisation that two of the germ-layers give rise exclusively or almost exclusively to one kind of tissue excited great interest at the time, and gave the direction to histogenetic research for quite a number of years, though in the end it turned out to be insufficiently founded.

Form and Function A Contribution to the History of Animal Morphology