994 MESSRS. LISTER AND FLETCHER ON THE [DcC. 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. 



Seller'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, how- 

 ever, it appears probable that the young passes through that open- 

 ing, because it is the 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 Dendrolaffus?) an opening is formed in the median canal to give 

 passage to the young. Tliis may take place early in life (Halma- 

 turus), or not till young are about to be produced {Macropus) . 



In the species Macropus tnajor, however, this opening may or 

 may not exist, and the young may be transmitted either through the 

 median or the lateral canal. 



In the genus Hypsiprijmnus 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 (6) 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 



