The Rohon-Beard cells were investigated during the development of Jordanella floridae, an oviparous Teleost. These neurons begin to differentiate when the embryo is 1,5 mm long, are completely differentiated in the embryo 2,5 mm long and are lacking at the 3rd day after the matching. As in previous works no Rohon-Beard cells were found in Gambusia and Poecilia, viviparous fishes belonging to the same order of Teleosts, the presence of Rohon-Beard cells in Jordanella must be related to the conditions of embryonal development. The rate of differentiation and involution of Rohon-Beard cells in Jordanella and Brachydanio, another oviparous Teleost, is different and related to the morphogenesis of spinal ganglia.