CHAPTER XII 



ADJUSTMENT, DIRECT AND 

 INDIRECT 1 



/^ N objection much less obvious than the 

 A-\ two considered in the foregoing chapter 

 •^ -^ is brought up by Mr. Mivart against 

 the theory of natural selection. In the Cuvier- 

 ian classification, the marsupials were ranked as 

 an order of mammalia, side by side with orders 

 like the carnivora or rodentia. This arrange- 

 ment is now obsolete. The class of mammals is 

 no longer directly divided into orders, but is 

 first separated into three sub-classes, the mono- 

 delphia, didelphia, and ornithodelphia. The lat- 

 ter sub-class, forming the link between mam- 

 mals and sauroids, is now nearly extinct, being 

 represented only by a single order, containing 

 two genera, the Australian echidna and duck- 

 bill. Leaving these aside, all other mammals, 

 except the marsupials, are comprised within the 

 sub-class monodelphia. The didelphia or mar- 

 supials are divided by Professor Haeckel into 

 eight orders ; and between these orders and sun- 

 dry orders of the higher monodelphia there is a 

 ^ [See Introduction, § 19.] 



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