Fig. 2. Telencephalons that lack Fgfr1 do not develop normal olfactory bulbs. Ventral views of E13.5 control (A) and mutant (A') brains showing a lack of OB development in the mutant (arrow; anterior is upwards). Scale bar: 0.75 mm. Dorsal views of E16.5 control (B) and mutant (B') brains; OBs are absent from the mutant (arrow). At P0, control brains (C) have well developed OBs, whereas mutants (C') have a small bulb-like protrusion (arrow). Scale bar for B-C': 1 mm. Cresyl Violet stained sagittal sections through the brains of control (D) and mutant (D') mice at E16.5 showing a lack of cellular organization in the anterior mutant telencephalon (arrowhead); the anterior telencephalon of mutants is no longer arranged in layers as it is in control embryos. Cresyl Violet stained sections through control (E) and mutant (E') brains at P0 showing a small bulb-like protrusion (arrowhead). cp, cortical plate; OB, olfactory bulb; vz, ventricular zone. Scale bar for D-E': 0.75 mm.