“…Phylogenetically, the VNO first appears in amphibians, is well developed in reptiles, but absent in birds [4,11,13,14]. In mammals, this organ varies in the development among species [12,14] , and is so far reported in rodents [7,20,27,28,301, rabbits [17,28], insectivores [211, carnivores [3,9,23] , bats [5], ungulates [2,9,15,26] and primates [16,19,24,251. Although rodents are used most frequently as experimental animals, fine structure of the VNO is hitherto examined only in the rat, mouse and golden hamster [7,20,27,28,30].…”