Iect. III.] EMBRYO OF THE MARSUPIALS. 59 



LECTUEE III. 



On the Marsupials, or Pouched Animals 

 (Metatheria). 



In their structure generally, the Marsupials are inter- 

 mediate between the Monotremes and the placental or 

 nobler forms of mammals (Eutheria). With regard to 

 the development of their embryo, these types are far 

 below the Eutheria, while they are most probably 

 above the Prototheria ; there, however, we are at a 

 •standstill for want of materials. 



In their early development these pouched mammals 

 •come very close to the higher oviparous animals 

 (ReptUes and Birds), but we have good reasons for 

 asserting that they are less specialised, or more archaic 

 than the existing members of the great group of 

 Sauropsida (EeptUes and Birds in one group). All 

 these kinds — the Reptiles, Birds, and Marsupials — may 

 have been on the same level once, — may have arisen 

 from the same old Amphibian stock — but the embryo 

 and its wrappings, in these mammals, is in some 

 important respects less developed than in the other 

 two groups. 



It is a very instructive fact that the tail-less Amphibia 



