90 EXPLANATIONS. 



being an order whose osteological structure is 

 allowed by every naturalist to be bird-like. New 

 and curious illustrations of the connexion be- 

 tween the birds and the implacental mammalia 

 are constantly appearing. We lately heard of a 

 bird which has a pouch for its young like the 

 kangaroo,* and Mayer has discovered in the 

 female emeu a purse form of certain organs, indi- 

 cating an approach to the marsupial in that part 

 of structure which is the most distinctive in the 

 case.f It would appear that the reviewer is 

 simply ignorant of this department of natural 

 history, and, with the self-esteem which often 

 attends upon ignorance, he has somewhat un- 

 luckily ventured to give a positive contradiction 

 to that which is inconte stably true. 



The reviewer at length comes to the organic 

 phenomena of the Tertiary system. " On the 

 theory of development," says he, " ' the stages of 

 advance are in all cases very small — from species 

 to species,' and the phenomena, ' as shown in 

 the pages of geology, are always of a simple and 

 modest character.' Let us test these assumptions 

 by one single step, from the chalk to the London 



* Magazine of Natural History. 

 I Reports of Ray Society, I. 



