The elements of Embryology (1889) The elements of Embryology elementsofembryo00fostuoft Year: 1889 22 THE HEN S EGG. Fig. 8. fCHAP, ' ^^'OQ'r- 'â â °d^' '®^0 o-^^ uuS©©® a ^' / Section of the Germinal Disc of a Fowl during the Later Stages of Segmentation. The section, which represents rather more than half the breadth of the blastoderm (the middle line being shewn at c), shews that the upper and central parts of the disc segment faster than those below and towards the periphery. At the periphery the segments are still very large. One of the larger segments is shewn at a. In the major
The elements of Embryology (1889) The elements of Embryology elementsofembryo00fostuoft Year: 1889 22 THE HEN S EGG. Fig. 8. fCHAP, ' ^^'OQ'r- 'â â °d^' '®^0 o-^^ uuS©©® a ^' / Section of the Germinal Disc of a Fowl during the Later Stages of Segmentation. The section, which represents rather more than half the breadth of the blastoderm (the middle line being shewn at c), shews that the upper and central parts of the disc segment faster than those below and towards the periphery. At the periphery the segments are still very large. One of the larger segments is shewn at a. In the majority of segments a nucleus can be seen ; and it seems probable that a nucleus is present in all. Most of the segments are filled with highly refracting spherules, but these are more numerous in some cells (especially the larger cells near the yolk) than in others. In the central part of the blastoderm the upper cells have commenced to form a distinct layer. a. large peripheral cell. b. larger cells of the lower parts of the blastoderm, c. middle line of blastoderm, e. edge of the blastoderm adjoining the white yolk. w. white yolk. In the later stages of segmentation not only do the first-formed segments become further divided, but seg mentation also extends into the remainder of the germi- nal disc. The behaviour of the nucleus during the segmenta- tion has not been satisfactorily followed, but there is,
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