284 
NATURE 
[JANUARY 21, 1904 
to a number of public schools is likely to be devised in the 
future. In conclusion, Mr. Latter was of opinion that 
nature-study might with advantage be extended to advanced 
biological work of the school and university laboratories. 
A discussion followed, in which the chairman, Mr. Hill, 
Mr. Shenstone, Mr. Talbot and others took part. Prof. 
Armstrong said that the phrase ‘‘ nature-study ’’ was simply 
a ‘““ war cry’? at present, and was being used by one party 
for something which was scientific neither in its intentions 
nor methods. Later on in the discussion the facts were 
mentioned that nature-study has a general educational 
significance, and is recognised in England as expressing 
the methods of science, but as being otherwise of an in- 
formal character. 
In reply, Mr. Latter said that all he wanted was that the 
boys should have their eyes opened, and a resolution was 
passed that a subcommittee should be appointed to com- 
municate with the preparatory schools in order to determine 
the form of science teaching best suited to their needs. 
WicrreD Mark WEBB. 
THE ORIGIN OF THE AUSTRALIAN 
MARSUPIALS. 
“THE relationships of marsupials in general to other 
mammals, the route by which their Australasian re- 
presentatives reached their present habitat, and the date 
of their arrival, are problems which have of late years 
attracted a large amount of attention on the part of 
naturalists, and are still far from being definitely solved. 
A bold and vigorous attempt to determine these questions 
has lately been made by a promising young Canadian 
zoologist, Dr. B. A. Bensley, of Toronto University, who 
a few years ago paid a visit to England for the purpose of 
studying the unrivalled amount of material in the British 
Museum. The final results of his investigations have just 
been published in the Transactions of the Linnean Society 
of London. Needless to say, this elaborate memoir is 
bristling with technicalities, and much of its contents is of 
far too abstruse a nature to be even touched upon in a 
journal like our own. Nevertheless, there are certain parts 
of more general interest which admit of notice. 
One of the difficulties which beset the study of the group 
has arisen from the discovery, by an Australian naturalist, 
that the bandicoots, unlike other marsupials, possess 
vestiges of a placenta, by means of which the maternal 
blood is brought into direct connection with that of the 
foetus, and the question is whether this implies a much 
nearer relationship between marsupials and = ordinary 
placental mammals than has been generally supposed to 
exist. Dr. Bensley answers the question in the negative, 
believing the bandicoot placenta to have had an independent 
origin. He may, of course, be right in this surmise, but 
it must always be remembered, as in analogous cases, that 
this is a summary, if convenient, way of getting rid of 
difficulties. Even, however, on this view, the author is of 
opinion that the relationship between marsupials and 
placentals is much more intimate than was believed to be 
the case by the older naturalists. 
As the result of the investigations of several modern 
naturalists, the belief is gradually gaining ground that all 
the modern marsupials, with the possible exception of the 
Tasmanian wolf, or thylacine, are derived from a primitive 
arboreal type, of which the South American opossums (not 
the animals so miscalled in Australia) are now the only re- 
presentatives. This arboreal ancestry is chiefly displayed 
in the structure of the foot, and even the essentially 
terrestrial kangaroos can be easily traced, through the 
phalangers (the miscalled opossums of Australia), into con- 
nection with an arboreal type. Somewhat curiously, it may 
be mentioned in passing, certain members of the former 
group—to wit, the tree-kangaroos—show a kind of reversion 
to the arboreal life of their ancestors. There are, however 
(as, indeed, would be manifestly impossible), no signs of re- 
version to the original grasping type of foot, tree-kangaroos 
hopping on the larger branches in the characteristic 
manner. 
The opossums, then, are the most primitive of living 
NO 1786, VOL. 69] 
marsupials, and since they date from the earlier portiom 
(Eocene) of the Tertiary period, they are likewise the earliest 
animals which can be definitely included in that group, for 
there is great doubt whether any of the small mammals. 
of the Secondary epoch (those, for instance, of the Stones- 
field slate and Purbeck beds) are really marsupials, or at 
all events marsupials as we now know them. 
The arboreal ‘‘ radiation ’’ (to use a term now extensively 
employed by American zoologists) of marsupials  differ- 
entiates them from the extinct creodonts, or primitive 
Carnivora, of the early Tertiary epoch, which appear to 
have been essentially terrestrial types. Nevertheless, by 
means of certain Middle Tertiary South American forms. 
(the so-called sparassodonts), these same creodonts appear 
to have been very closely connected with the thylacine, and 
thus with other marsupials, and this presumed relationship: 
seems to have considerably puzzled Dr. Bensley. For, 
while including that animal in the Dasyuride, he suggests 
that it may be an altogether foreign member of the 
Australian fauna, and that its origin may have to be sought 
elsewhere—presumably in South America. He adds that no 
signs of arboreal ancestry are to be detected in the 
thylacine’s foot. If this means anything, it seems to imply 
that the animal in question is not related at all to the 
typical arboreal marsupials, but that its kinship (unless 
the resemblances are due to “‘ parallelism in development ’’) 
is with the South American sparassodonts, and thus with 
the creodonts. But if so, it surely seems to follow that the 
creature is not, phylogenetically, a marsupial at all. The 
whole question seems a hopeless puzzle, and if the author 
cannot explain it, most surely we will not make the attempt- 
To turn to less debatable ground, great interest attaches 
to the author’s remarks concerning the huge extinct 
marsupial from Australia described by Owen as a carni- 
vere, under the name of Thylacoleo. Arguing from the 
resemblance of its dentition to that of the phalangers, later 
writers, however, came to the conclusion that the creature 
was herbivorous. This view is discredited by Dr. Bensley, 
who, following Dr. Broom, reverts to the opinion that it 
was a flesh-eater, which, as Owen suggested, may have 
preyed on the contemporary giant kangaroos or even the 
still more gigantic diprotodons. Nevertheless, it is believed 
that Thylacoleo was descended from herbivorous marsupials 
allied to the phalangers, and, this being so, it is not easy 
to see why the author assigns it to a family group by itself. 
This, however, is but a detail. 
The marsupials of Australasia, it is pointed out, must have 
come either from the north-west by way of the Malay 
Archipelago and Papua, or from the south through an 
Antarctic connection. Certain objections raised by Prof. 
Baldwin Spencer against a Malayo-Papuan route are dis- 
counted, but the author does not commit himself to any 
definite opinion as to the probable line of immigration. 
As to the date of the immigration, the author, after 
mentioning that one authority makes it Jurassic, a second 
Cretaceous, and a third Eocene, inclines to the opinion that 
it did not take place until the Miocene or middle division of 
Tertiary time. Although we incline to the view that it 
was probably Tertiary, so late an epoch as the Miocene 
seems to allow a very short period for the evolution of the 
numerous modern forms and their immediate ancestors. 
Later on, it is argued that opossums may be the de- 
scendants of Jurassic ancestors, or they may themselves be 
the original marsupials. Assuming the latter to be the 
case, it may be asked, was the arboreal marsupial radiation 
only Tertiary, and are creodonts (inclusive of the South 
American sparassodonts) and the thylacine developments of 
an earlier common terrestrial stock related to the still 
earlier mammal-like reptiles ? 
Summing up the evidence as to the diffusion of modern 
marsupials, the author is of opinion that during the 
Oligocene period there was a _ radiation of opossums 
throughout a large portion of the northern hemisphere, and 
that some of these animals gained an entry into South 
America, where they may have given rise to the extinct 
Microbiotheriide of Patagonia. Then came the immigra- 
tion into Australasia, during Miocene or Middle Tertiary 
time. About the same period occurred the great develop- 
ment of South American marsupials, such as the extinct 
Abderitidae and the forerunners (Epanorthidze) of the modern 
