OCR Text |
Show 1881.] VAGINAL APPARATUS IN THE MACROPODID^. 993 to show, that when the median canal is open and young have been born the young has passed through this opening on its way to the exterior, then the fact that this difference should exist" among females which have born young-a difference not only in form but also in function-appears most strange. With regard to the other species the evidence is far more satisfactory. Six specimens of Macropus rufus have been examined: four of them had born young, and the median canal was open ; two of them had not born young (one was not full-grown), and the canal was closed. This seems to show that in M. rufus an opening is formed in the median chamber either during pregnancy or at the time of parturition. The two other species of Macropus are isolated examples, and do not throw any additional light on the subject. The twenty examples of the genus Halmaturus may be considered together. It will be observed that in one young one (Luca's H. bennetti) and in one adult (Brass's H. bennetti) the median canal was found to be closed, and that in all the rest, including two other young ones (Brass's H. Bennetti and our II. ualabatus), it was open. This seems to show that in the genus Halmaturus the median canal may become open before the young have arrived at maturity, but that the thin septum which divides it from the urogenital sinus may remain perfect till after maturity is reached. In either case what evidence there is shows that after young have been born the canal is open. Our three examples of Petrogale xanthopus bear out the same idea; but whether the cul-de-sac is converted into an open canal early (as in some Wallabies), or not till young are about to be born (as in M. rufus), the evidence is not sufficient to decide. As to the specimen of Dorcopsis luctuosa and the three of Dendro-lagus inustus, the evidence as to whether young had been born or not is not conclusive. As far as it goes, however, it is in favour of the latter supposition. That the canal would be open when young had been born, however, in the present state of the evidence it would be rash to assert. The genus Hypsiprymnus offers a different condition from any we have considered : it had undoubtedly brought forth young ; and as undoubtedly the median canal is closed. So far our specimen agrees with the examples of Macropus major described by Prof. Owen, and with the "Kangaroo" described by Seiler. It differs from the former, however, in the fact that the muscular thickening and constriction in the lateral canals, which are present in all our other specimens, are here absent. Thus in this case, in which the young passed down the lateral vaginal canals, we find a condition of these canals different from that of any of the other Macropodidae which we have examined. The observations on the Kangaroos whose species are not given are in agreement with those already considered. Home's two examples are similar to those of Macropus rufus already described; but it is not stated whether young had been born. Puoc. ZOOL. Soc-1881, No. LXIV. 64 |