OCR Text |
Show 994 MESSRS. LISTER AND FLETCHER ON THE [Dec. 13, Carus's specimen, which had bred, corresponds with our example of Macropus major, with the other species of Macropus, and with the genera Halmaturus and Petrogale. Seiler's specimen agrees with Prof. Owen's examples of Macropus major; but the extent to which the canals are sometimes found plugged with mucus renders his experiment with quicksilver not perfectly conclusive. It appears not improbable that Prof. Owen's examples are identical with those of Macropus major referred to in his answer to Alix. These have been already considered. With regard to the course taken by the young in its passage from the uteri, when the median canal is closed it must, of course, pass by one of the lateral canals, whether they be thin-walled and with an even diameter all the way, as in Hypsiprymnus, or narrowly constricted at part of their course as in Macropus. When the canal is open, however, it appears probable that the young passes through that opening, because it is tbe directer route and there is no narrow strait to traverse-a view which is supported by the condition in which we found the vaginal canals in the specimen of Macropus rufus which had lately produced young, and also by the evidence with regard to the species M. rufus; for there is one nearly full-grown example which had not produced young in which the median canal is closed, while in four others which had produced young the canal was open. Conclusion. The following statements appear to be borne out by the evidence before us :- In the very early condition of the Macropodidee the median canal is closed. In some genera, viz. Macropus, Halmaturus, Petrogale (Dorcopsis and Dendrolagus ?) an opening is formed in the median canal to give passage to the young. This may take place early in life (Halmaturus), or not till young are about to be produced {Macropus). In the species Macropus major, however, this op2ning may or may not exist, and the young may be transmitted either through the median or the lateral canal. In the genus Hypsiprymnus the median canal remains closed, and the young passes down the lateral canals, which differ in their structure from those of the genera above quoted. Many more observations will be necessary before the question can be settled for the Macropodidae; and Alix's note on the Wombat shows that the open condition may be found outside the limits of this group. Note.-It may be well to state here the condition of the vaginal canals in the young specimen (B) of Macropus rufus. Owing to the very rudimentary condition of the reproductive organs, it is not easy to determine the sex from them. The structure was examined by means of sections cut transverse to the long axis of the |