The oculomotor nerves (3rd, 4th and 6th) of some species of fish and mammals have been studied to establish the presence, number, true topography and probable functional role of the ganglion cells located along the trunk. The finding of typical pseudo-unipolar ganglion cells is always unpredictable and extremely variable, from an inter- and intra-specific point of view, in members of the two zoological classes studied.