176 



T. THOMSON FLYNN 



The phylogenetic importance of the presence of large multi- 

 nucleate masses of foetal origin in the allantoplacenta of 

 Perameles, the dog, the rabbit, and others cannot be over- 

 estimated. 



Bearing in mind the accepted origin of the Metatheria 



Text-fig. 3. 



Fig. 3. — An early stage of development of the dog showing chorionic 

 attachment (after Schoenfeld). cyl., cytoblast ; ph., plasmodi- 

 blast ; ep., uterine epithelium. 



Text-fig. 4. 



Fig. 4. — A stage in Perameles comparable with that of the dog 

 in Text- fig. 3. Lettering as in Text- fig. 3. 



and Eutheria from a primitive diphyodont protoplacental 

 stock (Hill, 1897, p. 432), it is possible to state with certainty 

 that, in that early group, the same conditions of passivity of 

 the uterine epithelium and active phagocytic quality of the 

 trophoblast were already in existence ; with the further 

 differentiation of the latter layer in its placental portion into 

 two distinct layers, respectively cellular and plasmodial. 



The foregoing facts make this conclusion inevitable. This 

 being so, those Eutheria, particularly the Ungulata, 



