Fig. 2

In the majority of non-cartilaginous vertebrates, the posterior lateral line placodes migrate and deposit lateral line sense organs. (A) The posterior lateral line placode often splits into a dorsal and a ventral component, as seen in the mudpuppy Necturus (an aquatic salamander) (reproduced from Platt, 1896). (B) Fusion of the trunk of a lightly pigmented frog embryo (Rana palustris) with the head of a darkly pigmented embryo (Rana sylvatica) demonstrated that pigmented lateral line placodes from the head migrate onto the trunk where they deposit sense organs ( Harrison, 1904). (C,D) Stone (1933) transplanted pieces of Nile blue-stained donor ectoderm containing the posterior lateral line placode onto an unstained spotted salamander (Ambystoma maculatum; Ambystoma punctatum) embryo. (C) 2 days post-transplantation the stained club-shaped placode had started to migrate. (D) By 3 days post-transplantation, the placodes had migrated further and deposited sense organs