The facts to be mentioned in the following short notice have hitherto been not only imperfectly but erroneously described.
Since my arrival in Australia I have obtained considerable numbers of early embryos of various marsupial animals.
Of Phascolarctos cinereus (“Native Bear”) I have a very complete series of nearly 100 embryos in all stages from the unsegmented ovum onwards, while of the various kangaroo and wallaby types I have embryos in most of the stages. I shall not deal with the history of the germinal layers or of the general development in the present paper. The descriptions which follow holds especially for Phascolarctos cinereus and Halmaturus ruficollis.
These species represent two of the main divisions of the Marsupials, viz. (i) the short-faced opossum-like, and (ii) the long-faced kangaroo-like forms. I think it fair to regard the condition found in these as the typical marsupial one.
Both Phascolarctos and Halmaturos breed...
