The development of hippocampal and dorsolateral pallial region of the cerebral hemisphere in fetal rabbits. V. Sixty millimeter stage, glial cell morphology

The structure of the cerebral hemisphere of the 60 mm rabbit embryo was studied with aniline and Golgi stains. Two types of neuroglial cells are present for the first time at this stage and are described in detail: (1) Young neuroglial cells are elongate cells whose smooth somata are connected to an arbor of fine porcesses by a peduncle of varying length. They appear to develop from freely arborizing spongioblasts as somata lose their attachment to the ventricular surface and migrate toward the cortical plate. This suggests that astrocytes will be formed at a later state from freely arborizing spongioblasts rather than from typical spongioblasts whose connection to the pia has atrophied. (2) Small glial cells are present at all levels above the matrix lamina. They have small, smooth somata and fine, mossy processes arising from a short trunk at one pole of the cell. Although their origin is unknown, their small soze suggests they arise directly from germinal cells rather than from freely arborizing spongioblasts. Lacking conclusive evidence of their identity, they are tentatively regarded as a primitive type of oligodendrocyte.