I have not yet mentioned sound shifts between the different languages. I do not intend to enter into his subject here, for the sound systems of the individual languages are as yet unknown and it is very difficult therefore to say anything positive about them. There are a few exceptions, like Waropen, whose phonology is described in Held’s grammar (in the chapter “Klankleer”). For this very reason, it would be superfluous to discuss the phonological rules etc. of Waropen here. Biak has also been examined from the comparative linguistic point of view, by H. Kern, in his “Over de verhouding van het Nufoorsch tot de Maleisch-Polynesische Talen” (Actes du 6 e Congrès International des Orientalistes (Leiden, 1885)). I refer therefore to the existing literature.