XVI 
INTRODUCTION. 
to the animal, contracted in front, and its surface is smooth, or presents but few convolutions ; the cerebellum 
is entirely exposed, and has a vermiform process large in proportion to the lateral lobes ; the olfactory lobes 
are large. Two vena; cavse enter the heart ; “ the right auricle has no trace of a fossa ovalis.” In point of 
fact, the main characteristic of the Marsupials, as distinguished from the Placentals, is that much of the 
embryotic life in the former is carried on in what may be called a sort of external uterus. 
On my return from Australia, the venerable Geoffrey St. -Hilaire put the following question to me, “ Does 
the Ornithorhynclius lay eggs ? ” and when I answered in the negative, that fine old gentleman and eminent 
naturalist appeared somewhat disconcerted. Now, this oviparous notion was nearly in accordance with the 
true state of things — somewhat akin to what is actually the case ; and I consider the most striking peculiarity 
of this singular animal, and indeed of all the Mursupiata, to be the imperfectly formed state in which their 
young are horn. The Kangaroo at its birth is not larger than a baby’s little finger, and not very unlike 
it in shape : in this extremely helpless state, the mother, by some means at present unknown, places 
this vermiform object to one of the nipples within her pouch or marsupium ; by some equally unknown 
process, the little creature becomes attached by its imperfectly formed mouth to the nipple, and there 
remains dangling for days, and even weeks, during which it gradually assumes the likeness and structure of 
its parents ; at length it drops from this lacteal attachment into the pouch, re-attaches itself when hunger 
prompts it so to do, and as often again tumbles off when its wants have been supplied. It is scarcely 
necessary to say that, after gaining sufficient strength, it leaves this natural pocket of the mother, leaps into 
the open air and sports about the plains or the forest, as the case may be, and returns again to its warm 
home, until at length the wearied mother denies it this indulgence and proceeds again to comply with the 
law which governs all creatures, that of reproduction. This is a very low form of animal life, indeed the 
lowest among the Mammalia, and exhibits the first stage beyond the development of the bird. 
This description has reference not only to the Kangaroos, which mostly have hut one young at a time, hut 
is equally descriptive of the other members of this group, some of which have two, while others have three 
or four, and others, the Phascogalce for instance, eight or nine at a birth ; but in all cases, even with these 
large numbers, the young hang to the mammae in the way I have described. 
Independently of the low structure of the brain and the low form of reproduction of the Kangaroos, I 
ouo-ht to mention that two little bones have been expressly provided for the support of the marsupium ; 
there is also a considerable difference in the dentition, as well as in the form of the lower jaw, by which 
this group of animals may at all times be distinguished. I have not failed to notice much disparity in 
size in the Marsupiata ; they seem to he always growing ; for the males get larger and still larger for years, 
even long after they have commenced the duty of reproduction, and hence individuals of all sizes occur, and 
occasionally one extraordinarily large may be met with. I have observed this to occur with all the Marsupials, 
but particularly among the Kangaroos. The great herds of the grey species, Macropus major , are frequently 
headed by an enormous male, or Boomer as he is called. Like the “ rogue Elephants ” of Ceylon, these 
patriarchs are often solitary, and are generally very savage. 
Commencing with the most lowly organized of the Australian mammals, I may state that the Ornitho- 
rhynchus has a very limited range, as is shown by its not being found either in Western or Northern Aus- 
