Sites for the injection of polystyrene beads into the ventricles of anesthetised Xenopus larvae. A glass capillary filled with an aqueous suspension of red beads (2.9 μm in diameter) was inserted into the lateral ventricle (a, b) or the fourth ventricle (c, d) for injections. Arrows indicate the injection points. (b, d) magnified views of (a, c), respectively. Scale bars, 1 mm (a, c) and 0.5 mm (b, d).