The female urogenital system of the Marsupialia with special reference to the vaginal complex

Abstract

It is proposed to discuss the general disposition of the female urogenital organs in the Marsupialia and in particular to examine the variations to be found in the vaginal complex. Special reference will be made to the genera PotoToiis and Bettongia, partly because the urogenital system of the former ha~ not been described or figured hitherto and also because the two genera have been confused by previous writers on marsupial comparative anatomy and it is important that the matter should be clarified once and for all (see Pearson, 1944). The foundation of our knowledge of the urogenital system of the Marsupialia was well and truly laid by Richard Owen, and after the lapse of a century students of comparative anatomy of the group find themselves returning to the admirable and, on the whole, accurate accounts of the urogenital system which the distin· guished comparative anatomist has placed on record. A second stage may be said to have been reached when Lister and Fletcher (1881) and Fletcher (1882, 1883, 1884) made a careful investigation of the vaginal cul-de-sac of the MacTopodidae and were able to confirm and supplement some of the observations on marsupial parturition which had first been made by Home as far back as 1795 and later by Owen, Alix (1879), Brass (1880) and others. Perhaps the most fruitful period is associated with the name of ,J. P. HiIl who since the concluding years of the last century has issued a series of monographs dealing with the compal'ative anatomy of the urogenital system and more particularly with the embryology of the Marsupialia. In the course of their anatomical researches Hill (11'99, etc.) and Hill and Fraser (1925) have rounded off the earlier work and have demonstrated that the marsupials have forsaken the primitive parturient route by way of the MUllerian ducts and have acquired secondarily an amazing method of parturition by a direct median passage. The above names are those which come most readily to mind, though many other investigators have made valuable contributions to our knowledge of the morphology or the marsupial urogenital system. The Prototypal Marsupial (Text fig, 1) In attempting to reconstruct the urogenital system of the ancestral marsupial one is confronted by an intriguing and difficult problem. The evidence of the cemparative anatomy and embryology of recent forms requires careful handling, and those best qualified to judge are hardly in accord reg'arding the prototypal plan on which the marsupial urogenital system was laid down or in the interpretation of' the method of' evolution which followed. There is complete agreement, however, that the arrangement of' this system in modern marsupials, though showing' considerable variation, is based upon a common 71