316 
others partially divided ; but the divided por- 
tion in the latter is always that which is nearest 
the urethro-sexual passage. 
The true uterus is completely divided in all 
the Marsupial genera, and each division is of a 
simple elongated form, as in the Rodentia. 
The superadded complications in the female 
generative organs of the Marsupials, as com- 
with other mammals, are not then rightly 
attributable to the uterus, but to the vagina; 
and they are of such a nature as to adapt the 
latter to detain the feetus, after it has been ex- 
pelled from the uterus, for a longer period than 
in other Mammalia. 
These complications vary considerably in the 
different marsupial genera. On a comparison 
of the female organs in Didelphys dorsigera, 
Petaurus pygmeus, and Petaurus taguanoides, 
in Dasyurus viverrinus, in Didelphys Virgi- 
niana, in Macropus major, and Hypsiprymnus 
murinus, I find that the relative capacity which 
the uteri bear to the vagine diminishes in the 
order in which the above-named a are follow, 
while the size of the external pouch increases in 
the same ratio. 
In Didelphys dorsigera the uteri (fig. 139, 
¢, ¢,) rather exceed the unfolded vagine in 
Fig. 139. 
Didelphys dorsigera. 
length. In most Marsupials the vagine at 
first descend as if S: commaeaicaleet directly 
with the urethro-sexual passage; but in this 
small Opossum, in which the abdominal pouch 
consists of two slight longitudinal folds, and 
the young, as is implied by its trivial name, 
are transported by the mother on her back, 
each vaginal tube (e, e, fig. 139,) after em- 
bracing the os tince (d), is immediately con- 
tinued upwards and outwards, then bends 
downwards and inwards, and, after a second 
MARSUPIALIA. 
bend upwards, descends by the side of the 
opposite tube to terminate re with th 
extremity _—_ wee in the commot 
or uro-genital passage (f'). 
In the Petauri, the vagina, when unfolk 
are a little longer than the uteri. On examinin 
a specimen of the Pigmy Petaurist which hai 
two very small young in the pouch, I fou 
both the true uteri of three times the di mete 
of the same in an unimpreguated specimer 
but the vagine were unaltered in size, it 
cating that the situation in which gestati 
takes place in this species is the same as in th 
Kangaroo. The vagine, after receiving th 
uteri, descend close together half-way toward: 
the commencement of the urethro-sexual pa 
sage, but do not communicate together in th 
part of their course. From the upper part | 
these culs-de-sac they are continued upware 
and outwards, forming a curve, like the ha 
dles of a vase, then descend, converge, am 
terminate close together, as in the precedin 
era sh i 
In rus viverrinus and Didelphys Vir 
Pee ey mesial culs-de-sac of a gin 
descend to the urethro-sexual passage, and ar 
connected to, but do not communicate with it 
The septum dividing them from each other is 
complete, being composed of two layers whic 
can be separated from each other, and which 
result indeed from the apposition and mutu 
cohesion of the vagine at this part. In ore 
to reach the common passage, each tube is con- 
tinued outwards from the upper end of the cul- 
de-sac, and forming the usual curve, terminates _ 
parallel to the orifice of the urethra. Th 
vagine in the Dasyures are smaller in propor- 
tion to the uteri than in the Virginian Opossum, 
but of a similar form. i. 
> 
ip 
of the mesial culs-de-sac of the vagine was im- 
perfect; but it is doubtful whether this inter- 
communication was not the result of parturition, 
or of an accidental rupture in the specimen ex- 
amined. If it should prove to be a specific 
difference of structure, it is an approximation 
to the condition of the female o in the 
Phalangers, the Wombat, and the Kangaroos. 
In the Macropus major the vagine (fig. 138, 
e, & ) preponderate in size greatly over the uter 
(c, c’); and, the 8 (e”) of the descending 
cul-de-sac being always more or less incom= 
plete, a single cavity (e) is thus formed, into 
which both uteri open ; but however imperfect 
the septum may be, it always intervenes and 
preserves its original relations to the uterine 
orifices (d, d). he. 
The foetus has been conjectured to pass into 
the urethro-sexual cavity by a direct aperture 
formed after impregnation at the lower blind — 
end of the cul-de-sac, but I have not been able — 
to discover any trace of such a foramen in two — 
kangaroos which had borne young; and be- — 
sides, I find that this part of ihe vagina is not | 
continuous by means of its proper tissue 
* Buffon, Hist. Nat. tom. x. p. 279. 
