EMBRYOLOaY OF THE MARSUPIALIA. 13 



concluding the description of this stage I may remark that, 

 since the completion of my previous paper on the placenta- 

 tion of Perameles, I have discovered that the native cat, 

 Dasyurus viverrinas, is also provided with a placental 

 connection of a somewhat complex nature and probably of 

 yolk-sac origin, but whether or not there is also present an 

 allantoic placental connection I am unable to state. My 

 series of stages is as yet very incomplete, and does not 

 permit me to enter into details, but it is certain that over 

 some portions of the inner surface of the uterus there is 

 present a syncytial layer formed by the fusion of the ectoderm 

 of the bilaminar omphalopleure with the uterine epithelium, 

 the nuclei of which form nests, vividly recalling the similar 

 nuclear nests of the syncytium of Perameles, and this conjoint 

 layer is vascularised by maternal capillaries. But whereas 

 in Perameles the syncytium clothing the inner surface of the 

 uterus is entirely of maternal origin, being derived from the 

 uterine epithelium, in Dasyurus it is partly of foetal origin 

 (fcetal ectoderm) and partly of maternal origin (uterine 

 epithelium) . 



The fcetal membranes are left behind in the uterus after 

 parturition, and, as in Perameles, the fcetal and maternal 

 portions of the placenta are absorbed in situ through the 

 agency of maternal leucocytes. In other words, the placenta 

 of Dasyurus, like that of Perameles, is contra-deciduate in 

 character. We have, then, in any discussion bearing on the 

 general question of the significance of the occurrence of an 

 allantoic placenta in Perameles, to face the fact that a placenta 

 of the contra-deciduate type has been found to exist in two 

 distinct genera of Polyprotodont Marsupials, and that the 

 uterine epithelium in both forms undergoes an essentially 

 similar transformation into a syncytium vascularised by 

 maternal capillaries. 



