

V E B T E B K A T A. 





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KANGAROOS. 



ORDER 13. MAHSUPIALIA OR MARSUPIATA.* 



This order derives its name from marsupinm, the Latin for purse or bag, the females of the sev- 

 eral which constitute it having under the belly a pouch or sac, in which the young, which 

 born in a very immature state, are received and nourished, and whither they retreat long after 

 ile to move about. The physiology as well as the osseous structure of all these ani- 

 mals most of course be adapted t<> this most curious system; but in other respects they vary 

 itly in size, form, and habits. The species are mostly confined to Australia, that strange quar- 

 ter of the globe, where cherry-stones grow on the outside of the pulp; where the big end of a 

 ittached to the stalk ; where nettles, ferns, and grasses grow into trees, and lilies, tulips, and 

 honeysuckles assume almost the substantial form of oaks. Before the discovery of New Holland, 

 ropeans had become acquainted with the opossum in America, and we may conceive their 



divide the Mammalia into two groups, the Placenturin and Aj>I<icentaria. In order to show 



■I of tlii--. it ':■ that it is well established that in the production, or, more properly, the n 



• '.able aa well aa animal, it i> necessary that the Germ-cell and the Sperm-cell should combine, 



principle of growth being in the latter, and communicated to the former by this union, in which the germ-cell is 



I by the Blaments of the -perm-cell. The germ-cell in the mammalia is the simplest form of what we call 



ided by the oviary of the female; this being fecundated by the sperm-cell, is brought into the 



gradually grows into the tiring being which, at the proper time, is born. During this process of 



i womb b (cento, and through this it maintains its connection with the mother 



nnd •■ for its support and growth. The animals thus nursed bj means of the placenta, are all brought 



•renter or leas maturity before birth, and hence those subject to this system are called Placeniaria. In 



imals noticed in the preceding pages are included. But we are now about to examine another 



n which, though the origin of reproduction is the same as we have described, the young, 



i l"-in_' nursed t" maturity by means of a placenta, are brought forth while yet in embryo, and are nursed 



in a pouch sit the abdomen of the mother. These are called Aplacentaria. It is apparent that this system of 



repr what approaches that of birds and reptiles, in which the ovum or egg itself is produced and then 



lually by incubation. A.8 we might exp set from such a circumstance, the aplaceutia arc generally of a lower 



■ mammalia, 



