With Plates 29—33.
IN a preliminary note (1) communicated to the Linnean Society of New South Wales I recorded the occurrence of an allantoic placenta in Perameles obesula, and gave a short account of its structure based on an examination of a single stage, at that time the only one in my possession. Since then, the acquisition of certain important earlier and later stages has enabled me to study the placentation of Perameles in some detail, and the results of this investigation are presented in the following pages. I am now able not only to amplify the short statement of the preliminary note, but to give a fairly connected account of what I believe are the most important phenomena in the evolution of the Perameles placenta. I am also now able to state that an allantoic placenta in all respects similar to that of P. obesula occurs in...
