CHAPTEE XIL 



ADJUSTMENT, DIEECT AND INDIRECT. 



An objection much less obvious than the two consiclered in 

 the foregoing chapter, is brought up by Mr. Mivart against 

 the theory of natural selection. In the Cuvierian classifica- 

 tion, the marsupials were ranked as an order of mammalia, 

 side by side with orders like the carnivora or rodentia. This 

 arrangement is now obsolete. The class of mammals is no 

 longer directly divided into orders, but is first separated into 

 three sub-classes, the monodelphia, didelphia, and ornitho- 

 delphia. The latter sub-class, forming the link between 

 mammals and sauroids, is now nearly extinct, being repre- 

 sented only by a siugle 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 marsupials are 

 divided by Prof. Haeckel into eight orders ; and between 

 these orders and sundry orders of the higher monodelphia 

 there is a curious parallelism. For example there is an order 

 of edentate marsupials, there is a marsupial order of carnivora, 

 and another of insectivora, and another of rodents, while the 

 kangaroo strongly resembles the sub-order of ruminants, and 

 the opossiim is clearly related to the lemurs, or lowest of the 

 primates. It becomes, '.hen, an interesting problem to settle 



