Fig. 4. The strip grafts (type 4) contribute to the cerebellar midline but produce none of the main cerebellar cell types. Sagittal sections through the MHB region of E16 (A-D) and E18 (F,G,I,J) chick-quail chimeras that received type 4 transplants. (A,B) The grafts contribute to the velum medullaris (arrowheads) and to the medial cerebellum (arrows). (C,D) Higher magnifications illustrating the graft-derived cell types. None of the grafts produced granule cells or deep nuclear neurons. Half of the grafts produced typical cerebellar cell types i.e. Purkinje and Golgi cells (arrowheads in C and F). The other half produced exclusively glial cells and interneurons of the molecular layer (D) suggesting that they arose from the frontier of the cerebellar anlage. (E,H) The number of molecular layer interneurons that express GAD67 increases significantly between E16 and E18 in the normal chick embryo. (F,G,I,J). The grafts produced only scarce Purkinje cells (F) or molecular layer interneurons (G), both detected by parvalbumin immunohistochemistry, a few QH1-positive vascular elements in the molecular and granular layers (I), and some astrocytes (J).