224 THE MONOTREMATA. [CH. V 



dug up in Australia and in its furthest corner, viz. 

 Queensland. Furthermore, as the colonists know to their 

 cost, the common rabbit when artificially introduced has 

 proved capable of suiting itself with a marvellous degree 

 of success to the conditions found in Australia. In this 

 latter case no competition has had the least effect; and 

 even when hampered by repressive legislation aided by 

 the experiments of bacteriologists the rabbit has done a 

 good deal more than hold its own. It is clear therefore 

 that there is nothing in the " air " of Australia which is 

 in any way fatal to the constitutions of mammals in 

 general. Then why, if the Marsupials have disappeared 

 elsewhere, have they not also disappeared from Australia ? 

 The key to the explanation of this difficulty seems to be 

 the assumption that Australia is the native country of 

 that group. It will be remembered that in Australia 

 alone and in some adjacent territories (New Guinea) are. 

 there any representatives of the oldest order of Mammalia, 

 the Monotremata. The two existing genera Echidna and 

 Ornithorhynchus are unknown save in this part of the world. 

 It is generally accepted that the Monotremata stand 

 at the base of the mammalian series and that the 

 Marsupials stand between them and the higher mammals ; 

 the name Metatheria applied by Mr Huxley to the group 

 is an expression of this opinion. The very fact that 

 Marsupials abound in Australia is so far a proof that they 

 Originated there ; for they would have died out were they 

 not so suited. Over-population or the migratory instinct 

 caused many forms to leave the Australian region and to 

 spread over Europe and America, in which latter country 



