The existence of tubes in the enamel of marsupials was first demonstrated by Sir John Tomes (1) in 1849, and most of our knowledge of tubular enamels is due to the researches of this author and to those of his son, Mr. Charles Tomes. With regard to the nature of the tubes in marsupial enamel, two very different views have been held. First, that of Mr. Charles Tomes, who considers that the tubes are canals in the centre of the prisms, calcification taking place centripetally, and leading in some cases to complete obliteration of the central channel as in human enamel, in others not reaching the centre and so leaving tubes within the prisms; and secondly, the view of Prof, von Ebner and Prof. Paul, who consider that the tubes lie, not within, but between the prisms.