MAMMALIA. 



195 



They walk on the flat foot ; have five toes on the 

 feet,*only the thumbs on the hind feet have no claws, 

 and are opposable to the fingers. The tail is very 

 long in all the opossums, hairy in part, and naked in 

 the other parts. They are covered with pretty close 

 fur; and like the insectivorous mammalia they have 

 the stomach simple. 



They are animals of a rank and offensive smell, re- 

 siding; in holes of trees during the day, and crawling 

 about and climbing during the night, levying their 

 contributions upon little birds and their eggs, as well 

 as upon insects. The Virginian opossum is the 

 largest, and it does not exceed the size of a cat. It 

 is furnished with a pouch ; and so are three or four 

 other species inhabiting South America ; some of 

 which frequent the rocks by the sea side, and feed 

 upon Crustacea?. Others of the same country, which 

 are not much larger than common rats, are without 

 the pouch ; but its place is marked by deep folds 

 along the side of the body. One species of Guyana, 

 which is about the size of a pole cat, has the feet 

 webbed, and its manners are understood to bear some 

 resemblance to those of the otters. 



Those which have been enumerated comprise the 

 whole of the American species, so far as these have 

 been discovered. They are, comparatively speaking, 

 an obscure as well as an useless race of animals ; though 

 in a country where insects are so exceedingly nume- 

 rous, every insectivorous animal is of some service. 



The marsupial animals of New Holland are much 

 more characteristic than the American ones ; and 

 there is a succession of them, answering in a great 

 measure to three or four different orders of the com- 

 mon mammalia. The colonists in Australia have 

 bestowed the names of common English animals upon 

 ;he greater number of them ; and this at first led to 

 mistakes respecting their natural history ; but those 

 mistakes have been in a great measure rectified. 



The genera of these Australian marsupial animals 

 are, Dasyurus, which are carnivorous animals ; 

 Parameh's, which have more the form of badgers, 

 though not very like those animals ; Phalangista, which 

 ire climbing and leaping animals ; Ptaurista, which 

 lave the skin of the sides formed into a parachute ; 

 Potorus, which resemble rats ; Kangurus, of the lead- 

 ug species of which we have already taken notice in 

 peaking of leaping animals ; Phascolarctos, which is a 

 imall animal, remarkably slow in its motions ; and 

 v /iascoloiys, which is also a very slow ground animal, 

 t is necessary to bear in mind, however, that those 

 halangers (Phalangista}, which have the tail naked 

 r covered with scales, are natives of the islands to the 

 ! orth cast of New Holland ; while those which have 

 he tails covered with hair are natives of New Hoi- 

 ind itself. Some species of these have been set 

 own as American, but it does not appear that there 

 any truth in their being natives ot that country. 

 \> these must be added, though in separate sections, 

 ie two most singular animals of Australia, or indeed 

 . f any part of the world. These are, the ornithorhyn- 

 ins. which is a swimming animal ; and the echidna, 

 liich is a burrowing one. There is no doubt that 

 iese two follow the general law of the marsupial 

 limals ; though a regular pouch would not be con- 

 sent with an animal which crawls and dabbles in 

 ud at the bottom of pools, or yet with one which 

 irrows rapidly in the ground. 

 The fact of these two animals having only one poste- 

 )r opening to the body, as is the cuse in birds, together 





with their jaws being drawn out into horny mandibles 

 something like those of birds, and like them destitute 

 of true teeth, were strong inducements to the natu- 

 ralists by whom they were first observed and 

 examined, and who had been in the habit of carrying 

 one type through each class of the vertebrated 

 animals, to look upon them as a kind of birds, or 

 perhaps as partaking of the characters of bird and 

 oviparous reptile, jumbled together with those of the 

 mammalia. Such a melange of character is, however, 

 inconsistent with all that we meet with in the other 

 parts of nature ; and though in the mammalia, whether 

 common or marsupial, there are very remarkable 

 differences of structure as suiting each to its proper 

 locality and office, yet there is not the slightest ten- 

 dency to blend the two characters of any two classes 

 in one and the same individual. This fact might have 

 been arrived at from what has til along been observed 

 of species, and species which, in structure, in food, 

 and in habits, approximate very nearly to each other. 

 From the great proximity between some of these, we 

 may conclude not with probability only, but with cer- 

 tainty as great as can be obtained upon such a subject, 

 that they could be blended together far more readily 

 than the characters of two classes ; but we find that 

 the line of distinction between species and species is 

 so clearly drawn, and so impossible to be permanently 

 broken, that not one new fertile species partaking of 

 the characters of two separate ones, can be introduced 

 by all the skill of the cultivator of animals, though he 

 labours with the utmost assiduity for the express pur- 

 pose, inasmuch as the animals of one generation which 

 he procures by this means, possess qualities which, for 

 certain purposes, are more estimable than those of the 

 pure animal of either species. 



If this holds true between species which are so 

 nearly allied to each other, and in all probability are 

 so nearly from the same original pastures as the horse 

 and the ass, the argument thence arising ought surely 

 to have been sufficient to show that there could be 

 no such blending as that which was alleged in the 

 case ot those animals, and more especially in that of 

 the ornithorhynchus, which was the earliest and the 

 best known. 



Other arguments, all tending to the same effect, 

 might have presented themselves in formidable array ; 

 for if there are any animals which have less occasion 

 than others for any of the attributes- of birds, they are 

 the very ones under consideration. Flying is the 

 proper bird character ; and flight might be much more 

 useful to, and therefore might be expected to be sooner 

 given to a mole or an otter than to either of those 

 animals. Besides, when birds lose their proper func- 

 tion, the capacity of flying through the air, they lose 

 in a great measure those parts of their bodies which 

 are the proper organs of flight. If they are swift- 

 footed animals, they have rudimental wings and 

 downy feathers, which serve them as balancers ; and 

 if they are slow-footed, the bones of the wings are 

 hardly, if at all, produced beyond the skin of the 

 side. If the wings are to be used as swimming 

 organs, as is the case with those aquatic birds which 

 are incapable of flight, there is a peculiar modifica- 

 tion to fit them for this office ; but there is in no case 

 the slightest tendency in the wing of a bird to take 

 the shape of a toed and clawed foot, as we find both 

 in the ornithorhynchus and the echidna. 



The skeletons of both animals are strictly those of 

 mammalia ; and in the articulations of the legs, there 

 N2 



