. Carnegie Institution of Washington publication. 368 THE DEVELOPMENT OF CERTAIN FEATURES OF THE CEREBELLUM. The cells have reached their greatest development in the flocculus. Those of the vermis are more uniformly developed than in any other portion of the cere- bellum, though the stage of their development is not so advanced as it is in the depth molecular layer. outer nuclear FIG 1.—Drawing of the cerebellar cortex in which each cell is repreeented in the field diawn. The most prominent feature of figure 1 is the transitory outer nuclear layer, which occupies a most superficial pos
. Carnegie Institution of Washington publication. 368 THE DEVELOPMENT OF CERTAIN FEATURES OF THE CEREBELLUM. The cells have reached their greatest development in the flocculus. Those of the vermis are more uniformly developed than in any other portion of the cere- bellum, though the stage of their development is not so advanced as it is in the depth molecular layer. outer nuclear FIG 1.—Drawing of the cerebellar cortex in which each cell is repreeented in the field diawn. The most prominent feature of figure 1 is the transitory outer nuclear layer, which occupies a most superficial position in the molecular layer. It disap- pears at different periods in different animals, correspond- ing to the age at which mye- linization in the cerebellum becomes pronounced and loco- motion acquired. This outer nuclear layer is probably ab- sorbed by the inner nuclear layer. of the floccular fissures. It should be mentioned that in a fetus of 6 months the Purkinje cells in the depth of a fissure show a development markedly beyond that of cells more superficially placed. This difference is illustrated in figure 2, a drawing of the contour of the flocculus; a and b indicate the positions in which the corre- sponding groups of cells are found. The cells in the depth of the fissure (a) show a denser protoplasm, a more definite contour, and better developed protoplasmic processes and nucleus than the more super- ^J\^ ^ ^ ^> ficially placed cells (6). The protoplasm of cells b, having no definite boundaries, merges into the surrounding proto- plasmic mass. It is less dense, hence the cells appear larger than cells o. This same difference is shown in figure 3 for the hemisphere. In the contour drawing a and b indicate the positions of the cell-groups o and 6. A comparison of the two figures shows how far the Purkinje cells of the flocculus are in advance of those of the hemisphere. In the seventh, as in the sixth month of prenatal life, the Purkinje cells of the vermis show
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