b'T.AOEMTA IN PRKAMELKS 143 



I'rom the above account it will be evident that the method of 

 tixation of the embryo to the uterine wall in this marsupial 

 is fundamently similar to the general type occurring in the 

 Eutheria. If, for example, the figures of this stage which I 

 have given (figs. 4. 5. (5. 7, 29, and Text-fig. 4) be compared with 

 the essentially similar drawings of the comparable phenomena 

 recorded by 8choenfeld for the dog (190B), (PI. xxii, figs. 14 

 to 17) (see Text-fig. 8), it will be seen that the difference in 

 the two forms rests mainly, in the early stages, on the behaviour 

 of the uterine epithelium. This, in the dog, remains as a distinct 

 layer until it undergoes degeneration as a result of the inroads 

 of the plasmodiblast. 



The Non-pregnant Uterus. — This was examined in 

 sections and found to have undergone changes corresponding 

 to those which had occurred in the right. The ovary of this 

 side, however, had a well-developed corpus luteum. I will, 

 therefore, not enter into a detailed description of the structure 

 of this uterus further than to mention the following : 



The epithelium has developed into a syncytium aljundantly 

 supplied with capillaries, many ramifying on the surface, some 

 of which discharge their blood by extravasation into the 

 lumen. A point of interest is the fact that, on the dorso- 

 mesial side of the uterus, the syncytium is somewhat thickened 

 and the mucosa is here developed into deep folds. At its edges 

 this thickening passes off gradually into the rest of the syncy- 

 tium. This thickened portion possibly represents the maternal 

 tropbospongia. Throughout the whole uterus the glands 

 show no degeneration. They are in an active state of secretion 

 and the inner ends of the gland-cells are torn and frayed out 

 through abundant breaking off of cell^^la.r secretion. Cilia, 

 therefore, are not to be found, 



(a) Significance of the Uterine Syncytium 

 in Perameles. 



Proliferation and syncytialization of the uterine epithelium 

 is a well-marked feature of maternal preparation for allan- 

 toic placentation in many Eutheria. In many cases the 



