THEIR POSITION IN THE ANIMAL KINGDOM. 9 



post-Linnaean system ; for the various genera differ 

 more from one another in structure, feet and teeth, 

 than do the members of other orders. That the 

 pig shows more affinity with the rhinoceros or with 

 the hippopotamus than with the ox, is anything 

 but self-evident as soon as it is clearly perceived 

 that the connecting link cannot be in the number 

 of hoofs. We may mention as isolated genera also 

 the camel, the giraffe, and the fingered-animals ; 

 and as isolated families all those animals which, on 

 account of their defective dental arrangement, may 

 be classed as animals poor in teeth (Edentata), 

 such as sloths, girdled animals, ant-eaters, and 

 scaled ant-eaters ; for even as groups they show 

 among one another a want of harmony similar to 

 that of the heterogeneous divisions of the class of 

 the many-hoofed animals. If, further, we draw 

 attention to the contrast in which the Marsu- 

 pials stand to all the other orders of mammals, 

 while they differ very widely among themselves, 

 we shall have pointed out a large number of 

 phenomena that are wholly unintelligible by them- 

 selves. 



In addition to this we meet with the many 

 geographical difficulties ; for instance, the geo- 

 graphical distribution of animals which, by itself, 



