PLACKNTA IN PEKAMELES IHl 



EXPLANATION OF PLATES O-IL 



Plate 9. 

 Figs. 1-8, 10-12, Pebameles obesula, 6-1 lum. Fig. U, Perameles 

 OBESULA, 12-5 mm. 



Figs. I, 2, and 3. — Sections shoAving the arrangement of syncytial 

 nuclei as a more or less irregular layer round a central cavity. Note the 

 vesicular shape and chromatic characteristics of these nuclei. Note also 

 intruding leucocytes. 



Figs, i, 5, and 6. — Phases in the earliest growth of the phismodiblast. 

 In tig. 4 the syncytial nuclei are already undergomg degeneration under 

 the effect of the plasmodial advance processes. 



Fig. 7. — Plasmodial attack on a gland. Note the breakuig tlown of the 

 gland epithelium on one side. Here also ingested material is evident m the 

 plasmodiblast. 



Fig. 8.- — Another stage in plasmodiblast formation. The cytoblast is 

 a well-detined layer. Note presence of leucocytes. 



Fig. 9. — Shows the vesicular and degenerate appearance of foetal 

 nuclei at this stage with close apposition of maternal and foetal vessels. 



Figs. 10, 11, and 12. — Photomicrographs of sections through a branched 

 gland just outside the area of the first fixation of the chorion (see Text- 

 fig. 1). 



Plate 10. 



Figs. 13-16, 19, Perameles gunni, 6-6 mm. Figs. 17, 18, Perameles 



OBESULA, 12-5 mm. Figs. 20, 21, Perameles obesula, 7 mm. 



Fig. 13. — Placental area towards the centre, showing the commence- 

 ment of the disorganization of the cytoblast allowing maternal capillaries 

 to approach the surface. The very superficial position of one "Df these 

 capillaries is, however, very exceptional for this stage. Note the penetration 

 of the plasmodiblast nuclei into the syncytial nests. 



Fig. 14.- — Section of somewhat more peripheral portion of the same area. 

 A distuict cytoblast is present and a plasmodiblast in which giant cells 

 and uigested material are outstanding features. This figure should be 

 compared with IMaxmiov's tig. 1 of the rabbit. 



Figs. 15, 16, and 17. — Show attachment of allantois and disorganization 

 of cytoblast to allow of the apposition of foetal and maternal blood-vessels. 



Figs. 17 a, b, c, d, e. — Stages in the degeneration of a foetal nucleus. 



Fig. 18. — Section of the central portion of the placenta showuig the 

 followmg : breaking down of cytoblast, almost complete tilling of syncytial 

 nests by foetal nuclei, penetration of allantoic capillaries and almost final 

 apposition of maternal and foetal blood-streams. 



