Fig. 1. DiI-labeling in the lamprey embryo. Embryos were injected focally with a single bolus of DiI. (A) Embryo fixed immediately after injection to show initial position of labeled cells. (B) Individual embryos were labeled at one of the four positions indicated along the anteroposterior (AP) axis (I, midbrain; II, rostral hindbrain; III, caudal hindbrain; IV, rostral neural tube). (C) Number of embryos labeled at each position and initial positions of labeled cells determined retrospectively after fixation.