LECT.IU.] DEVELOPMENT OF THE GERM. 89 







The dllantois does the same thing, beginning to form its mysterious 

 union with the lining walls of the uterus, as in the Eutherian embryo 

 at the same stage. 



But this strange union of the Shark method with the method of 

 the high Mammal is soon broken off, for, whilst yet a most minute 

 creature in the Virginian Opossum half an inch, in the Kangaroo an 

 inch, long the little creature is bom and placed by the mother in the 

 pouch, and on the nipple. 



During its pre-natal life the embryo develops very rapidly, and 

 the form, whilst so extremely small, is well finished, a new-born 

 kitten is scarcely better made, and it manages, in its new nursery, to- 

 hold on, tarrying nature's leisure, until its bones become well knit, 

 and its sinews strong. 



The single genus (Didelpliys, or the Opossums), still found in the 

 Western World, might yet, through long periods, and suffering from 

 mutability, gently and slowly become parental to any number or 

 kind of new Indectivore's ; but we shall not live to see such changes. 



The Eastern Marsupials, however, have, without transforming 

 into Insectivores, done some grand feats within their own circle, 

 pre-figuring in some degree several of the Orders of the higher sorts of 

 Mammalia. Their fossils show that some kinds were scarcely less 

 than the existing Elephants, whilst some living species have diminished 

 into a sort of pouch-bearing Mouse. 



Large or small, dead or living, they all have a kind of Keptilian 

 ' smack ' about them; and if the Mammalia had gone no higher than 

 the highest of the Marsupials, the Cosmos would have had no 

 terrestrial student, and the Author of all would have had no in- 

 telligent praise ascending to Him from the inhabitants of the green 

 earth. 



