The aim of the present study is to give a survey of the development of a teleostean cerebellum at all levels, from morphogenesis to cytogenesis. The trout was selected for this study since several investigators have studied the same species. Moreover, the trout is generally considered as a relatively simple teleostean fish. Where possible, morphogenesis and histogenesis are -3-considered in their mutual relationship. The results of the histogenetic analysis comprise lightmicroscopical and electronmicroscopical findings. Both neurogenesis and gliogenesis were studied.It will be shown that the cerebellum of the trout, although its form remains rather simple, develops into a highly differentiated structure, most of its neuronal and glial elements being directly comparable to those in mammals. The results will be discussed in light of current neuroembryological views and concepts.-2- In order to elucidate the spatial configuration of the cerebellum and adjacent structures during development, three-dimensional reconstructions in cluding the mesencephalon and rhombencephalon were prepared of the following stages: 7, 10.5, 11.5, 14, 15, 16 and 23 шт. All of these reconstructions are based on transverse H.E. stained series. The outlines of every third section were drawn at a magnification of 190 x. The drawings were transferred to styrofoam plates of 4 mm thickness, and then these plates were cut with a hot wire along the outlines of the drawings. Subsequently the plates were stacked, using sagittally sectioned series of the same stages as a reference. In addition a three-dimensional reconstruction was made of the brain of a trout of 230 mm at a magnification of 40 x.The terms sagittal, transversal and horizontal are used with respect to the main longitudinal axis of the brain.-4- side of the tegmentum a transversely oriented groove is visible, especially in the para-median regions, marking the boundary plane between mesencephalon and rhombencephalon as has been indicated already by von Kupf f er (t)6) and Palmgren ('21). This is the sulcus intra-encephalicus posterior. At the level of this groove the most rostral parts of the cerebellar anläge pass laterally into the tegmentum. We consider this groove to be an important landmark since the continuity between cerebellum and tegmentum at this level is maintained throughout development. The rostral tip of the cerebellar anläge will develop into a rostral direction but a fusion with the midbrain does not occur. Thus, although considerable transformations take place, the original relations are not changed.In the 6 mm embryo (14 days) the fissura rhombo-mesencephalica has become deeper, especially in the median plane. The orientation of the cerebellar primordium is more oblique than in the preceding stage; consequently, the recessus laterales of the fourth ventricle are narrowed. Just rostral to the lateral recesses bilateral thickenings appear on the brain wall, which represent the first parts of the vestibulolateral lobe. During further development these thickenings expand...

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The aim of the present study is to give a survey of the development of a teleostean cerebellum at all levels, from morphogenesis to cytogenesis. The trout was selected for this study since several investigators have studied the same species. Moreover, the trout is generally considered as a relatively simple teleostean fish. Where possible, morphogenesis and histogenesis are -3-considered in their mutual relationship. The results of the histogenetic analysis comprise lightmicroscopical and electronmicroscopical findings. Both neurogenesis and gliogenesis were studied.It will be shown that the cerebellum of the trout, although its form remains rather simple, develops into a highly differentiated structure, most of its neuronal and glial elements being directly comparable to those in mammals. The results will be discussed in light of current neuroembryological views and concepts.-2- In order to elucidate the spatial configuration of the cerebellum and adjacent structures during development, three-dimensional reconstructions in cluding the mesencephalon and rhombencephalon were prepared of the following stages: 7, 10.5, 11.5, 14, 15, 16 and 23 шт. All of these reconstructions are based on transverse H.E. stained series. The outlines of every third section were drawn at a magnification of 190 x. The drawings were transferred to styrofoam plates of 4 mm thickness, and then these plates were cut with a hot wire along the outlines of the drawings. Subsequently the plates were stacked, using sagittally sectioned series of the same stages as a reference. In addition a three-dimensional reconstruction was made of the brain of a trout of 230 mm at a magnification of 40 x.The terms sagittal, transversal and horizontal are used with respect to the main longitudinal axis of the brain.-4- side of the tegmentum a transversely oriented groove is visible, especially in the para-median regions, marking the boundary plane between mesencephalon and rhombencephalon as has been indicated already by von Kupf f er (t)6) and Palmgren ('21). This is the sulcus intra-encephalicus posterior. At the level of this groove the most rostral parts of the cerebellar anläge pass laterally into the tegmentum. We consider this groove to be an important landmark since the continuity between cerebellum and tegmentum at this level is maintained throughout development. The rostral tip of the cerebellar anläge will develop into a rostral direction but a fusion with the midbrain does not occur. Thus, although considerable transformations take place, the original relations are not changed.In the 6 mm embryo (14 days) the fissura rhombo-mesencephalica has become deeper, especially in the median plane. The orientation of the cerebellar primordium is more oblique than in the preceding stage; consequently, the recessus laterales of the fourth ventricle are narrowed. Just rostral to the lateral recesses bilateral thickenings appear on the brain wall, which represent the first parts of the vestibulolateral lobe. During further development these thickenings expand...

The aim of the present study is to give a survey of the development of a teleostean cerebellum at all levels, from morphogenesis to cytogenesis. The trout was selected for this study since several investigators have studied the same species. Moreover, the trout is generally considered as a relatively simple teleostean fish. Where possible, morphogenesis and histogenesis are -3-considered in their mutual relationship. The results of the histogenetic analysis comprise lightmicroscopical and electronmicroscopical findings. Both neurogenesis and gliogenesis were studied.It will be shown that the cerebellum of the trout, although its form remains rather simple, develops into a highly differentiated structure, most of its neuronal and glial elements being directly comparable to those in mammals. The results will be discussed in light of current neuroembryological views and concepts.-2- In order to elucidate the spatial configuration of the cerebellum and adjacent structures during development, three-dimensional reconstructions in cluding the mesencephalon and rhombencephalon were prepared of the following stages: 7, 10.5, 11.5, 14, 15, 16 and 23 шт. All of these reconstructions are based on transverse H.E. stained series. The outlines of every third section were drawn at a magnification of 190 x. The drawings were transferred to styrofoam plates of 4 mm thickness, and then these plates were cut with a hot wire along the outlines of the drawings. Subsequently the plates were stacked, using sagittally sectioned series of the same stages as a reference. In addition a three-dimensional reconstruction was made of the brain of a trout of 230 mm at a magnification of 40 x.The terms sagittal, transversal and horizontal are used with respect to the main longitudinal axis of the brain.-4- side of the tegmentum a transversely oriented groove is visible, especially in the para-median regions, marking the boundary plane between mesencephalon and rhombencephalon as has been indicated already by von Kupf f er (t)6) and Palmgren ('21). This is the sulcus intra-encephalicus posterior. At the level of this groove the most rostral parts of the cerebellar anläge pass laterally into the tegmentum. We consider this groove to be an important landmark since the continuity between cerebellum and tegmentum at this level is maintained throughout development. The rostral tip of the cerebellar anläge will develop into a rostral direction but a fusion with the midbrain does not occur. Thus, although considerable transformations take place, the original relations are not changed.In the 6 mm embryo (14 days) the fissura rhombo-mesencephalica has become deeper, especially in the median plane. The orientation of the cerebellar primordium is more oblique than in the preceding stage; consequently, the recessus laterales of the fourth ventricle are narrowed. Just rostral to the lateral recesses bilateral thickenings appear on the brain wall, which represent the first parts of the vestibulolateral lobe. During further development these thickenings expand...

The aim of the present study is to give a survey of the development of a teleostean cerebellum at all levels, from morphogenesis to cytogenesis. The trout was selected for this study since several investigators have studied the same species. Moreover, the trout is generally considered as a relatively simple teleostean fish. Where possible, morphogenesis and histogenesis are -3-considered in their mutual relationship. The results of the histogenetic analysis comprise lightmicroscopical and electronmicroscopical findings. Both neurogenesis and gliogenesis were studied.It will be shown that the cerebellum of the trout, although its form remains rather simple, develops into a highly differentiated structure, most of its neuronal and glial elements being directly comparable to those in mammals. The results will be discussed in light of current neuroembryological views and concepts.-2- In order to elucidate the spatial configuration of the cerebellum and adjacent structures during development, three-dimensional reconstructions in cluding the mesencephalon and rhombencephalon were prepared of the following stages: 7, 10.5, 11.5, 14, 15, 16 and 23 шт. All of these reconstructions are based on transverse H.E. stained series. The outlines of every third section were drawn at a magnification of 190 x. The drawings were transferred to styrofoam plates of 4 mm thickness, and then these plates were cut with a hot wire along the outlines of the drawings. Subsequently the plates were stacked, using sagittally sectioned series of the same stages as a reference. In addition a three-dimensional reconstruction was made of the brain of a trout of 230 mm at a magnification of 40 x.The terms sagittal, transversal and horizontal are used with respect to the main longitudinal axis of the brain.-4- side of the tegmentum a transversely oriented groove is visible, especially in the para-median regions, marking the boundary plane between mesencephalon and rhombencephalon as has been indicated already by von Kupf f er (t)6) and Palmgren ('21). This is the sulcus intra-encephalicus posterior. At the level of this groove the most rostral parts of the cerebellar anläge pass laterally into the tegmentum. We consider this groove to be an important landmark since the continuity between cerebellum and tegmentum at this level is maintained throughout development. The rostral tip of the cerebellar anläge will develop into a rostral direction but a fusion with the midbrain does not occur. Thus, although considerable transformations take place, the original relations are not changed.In the 6 mm embryo (14 days) the fissura rhombo-mesencephalica has become deeper, especially in the median plane. The orientation of the cerebellar primordium is more oblique than in the preceding stage; consequently, the recessus laterales of the fourth ventricle are narrowed. Just rostral to the lateral recesses bilateral thickenings appear on the brain wall, which represent the first parts of the vestibulolateral lobe. During further development these thickenings expand...