MAMMALIA. 



193 



the descendants of the shepherds founded the city, 

 reared the palace, established the law, cultivated 

 science, improved art, and enjoyed happiness. This ii 

 part of what we owe to the ruminant mammalia ; the 

 whole tale of their value and advantages is too long 

 to be told. 



MAUSUPIALIA. In stating our reasons for removing 

 these animals from the end of the flesh-eating order, 

 we took occasion to remark that they ought, in strict 

 propriety of arrangement, to form a sub-class, or a 

 separate class altogether from the regular mammalia, 

 because the character by which they are all distin- 

 guished, and upon which they are named, does not 

 belong to any of the rest. This character is the 

 attachment of a mamtpium, that is, a purse or pouch 

 on the under part of the females, which pouch is 

 supported by two peculiar bones called marsupial 

 bones for the sake of distinction ; and the degree of its 

 development varies in the different genera, and also 

 in the same female when in different states. In some 

 it is always largely produced, and answers as a re- 

 ceptacle to the full-grown young ; while in others it 

 is so little produced at any time, that it never covers 

 the teats of the animal. There are, indeed, cases in 

 which the pouch is little more than a ridge or fold 

 upon each side of the belly laterally ; but the bone 

 exists to some extent or other, even where the dis- 

 tinct pouch is wanting, and thus the whole of these 

 singular animals are brought into one class ; and 

 there would be no objection to consider them as an 

 order, only they do not strictly agree with the other 

 orders of the mammalia, in any great particular either 

 structural or physiological. 



The bones which support the marsupium are 

 attached to the pubis, and embedded among the ab- 

 dominal muscles, so that the pouch is retained in its 

 place with a degree of force proportionate to the 

 strain which it has to bear. We may see in part the 

 use of the singular structure of these females. Their 

 habit requires that they shall be much in a slanting 

 or upright position ; and the strength of their muscles 

 being, in the more characteristic species, concentrated 

 upon the loins and haunches, uterine gestation, until 

 the young were well advanced, would neither be con- 

 venient nor safe, accordingly there is a different 

 arrangement of parts in them, and instead of there 

 being but one opening to the uterus, as in the proper 

 mammalia, there are two canals of comparatively 

 small diameter, and curved in their direction. There 

 are in the organs of the other sex peculiarities 

 which answer to these ; and though the formation is 

 certainly singular as compared with that of the mam- 

 malia, the adaptation which it evinces is nowise 

 inferior, only as the habits of the animals are not 

 very well known, and as they were for a long time 

 considered and classed with the others, and their 

 more remarkable peculiarities passed with little notice, 

 the proper study of them may be said to be little 

 more than in its infancy. 



There is no doubt, however, that the whole of the 

 animals have a double gestation -a gestation in the 

 pouch, and a gestation previous to that in the internal 

 uterus. It has not been very satisfactorily made out 

 whether the young, when in the uterus, have or have 

 not a regular placenta ; but the analogy is against 

 their having one in any considerable state of deve- 

 lopment ; and in those species which have been 

 observed, the young, when they leave the uterus and 

 be transferred to the pouch, are too rudimental for 



NAT. HIST.-VOL. III. 



having an umbilical cord in any state of development, 

 They are far more minute and formless than the 

 young of any of the mammalia, not excepting those 

 which come into the world blind and naked ; and in 

 some species at least (for the greater number have 

 not been examined with sufficient care), they are 

 without any produced members, or any decided marks 

 of systematic action of any kind. The female trans- 

 fers them to the pouch with her mouth, or applies 

 them to the teats in those instances where these are 

 not covered by the pouch. It is upon the nipple or 

 teat, indeed, that the young one is suspended, and 

 not by the mere pouch ; and when very rudimental 

 ones are removed from the teat, they cannot regain 

 it without the mother's assistance, and thus they 

 would perish in the pouch without being able to help 

 themselves. 



It is of course not known whether all the species 

 are equally rudimental when placed in the pouch, or 

 indeed, whether the same female places all her young 

 ones in it at the same age. This is most probably 

 the case ; but the point is one upon which we cannot 

 speak positively, and, indeed, the whole doctrine of 

 the production of these animals, is one which must 

 be worked out upon its own data, without any ana- 

 logy drawn from the other mammalia. In those specieg 

 which have been open to accurate observers, the 

 whole period of gestation, at least up to the perfect 

 formation of the young animal, though not of course 

 to its growth, has been found nearly equally di- 

 vided between the womb and the marsupium ; 

 only the young ones take shelter in the latter after 

 they are capable of finding the greater part, if not 

 the whole, of their own food. Where this is the case, 

 the marsupium is of course considerably enlarged ; 

 but it is not in this that the principal office of this 

 organ consists. In its internal covering, partially 

 also in its teats, and perhaps wholly in these in some 

 of the species, this part of the system is only tem- 

 porary and developed when nature requires it, and 

 disappears again when the necessity for it ceases. 



The minute description of the curious economy of 

 these animals is not very well adapted for popular 

 illustration ; and though it were so adapted, it is too 

 scanty for admitting of being made satisfactory. We 

 may remark, however, that by far the greater number 

 of the marsupial animals are either leapers or climbers ; 

 and this peculiar arrangement of the organs of gesta- 

 tion is evidently intended to enable the loins and 

 haunches to have more powerful action in this way 

 than they would have if the animal were loaded with 

 full grown young. The double internal uterus and 

 the marsupium also enable these animals to bring for- 

 ward a succession of young ones at the same time ; 

 and they may be observed in the pouch at evidently 

 different ages in the different individuals which are 

 there at the same time. 



All those circumstances point strongly to the fact 

 that these animals are subjected to considerable hard- 

 ships and contingencies ; and this agrees with the 

 characters of those countries which the greater num- 

 ber of them inhabit. These are chiefly seasonal 

 countries, in which there is much alternate parching 

 and flooding countries in short which are not well 

 adapted for the common mammalia in a state of na- 

 ture ; and accordingly we find that in New Holland, 

 which may be considered the head-quarters of mar- 

 supial animals, there are no native placental mam- 

 malia, and such mammalia are not very common in 

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