The Yolk-Sac and Allantoic Placenta in 

 Perameles.^ 



By 

 T. Thomson Flynii, D.Sc, 



Ralston Professor of Biology, University of Tasmania. 



With Plates 9-11 and 4 Text- figures. 



Contents. 



1. Introduction ....... 



2. Review and Criticism of Previous Work 



3. Material ........ 



4. Terminology ....... 



5. Descriptive Account of Material 



Stage 1. Perameles obesula, 6-1 mm. 



[a) Significance of the Uterine Syncytium in Perameles 



(b) General Remarks on the Fixation of the Embryo 

 Stage 2. Perameles gunni, 6-6 mm. . 

 Stages. Perameles obesula, 7mm. . 

 Stage 4. Perameles obesula, 8-8-75 mm. . 

 Stage 5. Perameles obesula, 12-5 mm. 

 Stage 6. Perameles n a s u t a , post- partu m . 



6. Summary of Conclusions ..... 



7. Concluding Remarks ...... 



(«) The Placental Conception . 

 (6) Placental Phases m Perameles 

 (f ) Placental Phenomena in Marsupials generally 

 {(l) The Relation of the Allantoic Placentation of Per a 

 meles to that of the Eutheria . 



8. Papers referred to in the Text 



9. Description of Figures ..... 



page 

 124 

 126 

 134 

 135 

 136 

 136 

 143 

 145 

 147 

 158 

 162 

 162 

 165 

 165 

 168 

 168 

 171 

 172 



175 

 178 

 180 



* The present communication was awarded the University Medal when 

 presented to the University of Sydney as a thesis for the degree of Doctor 

 of Science. The absolute necessity, in the present time, of reducing 

 publication costs to the minimum, has resulted in the omission of some 

 of the original figures, these being reduced from fifty-two to the present 

 limit. 



