VIVIPAROUS ANIMALS. 401 
germination or evolution appears to take place in quadru- 
peds according to two different plans. In the first, there 
is no adhesion of the germ to the walls of the uterus, while, 
in the second, placentation or adhesion takes place. 
In the Marsupial genera, which we have seen are fur- 
nished with a complicated uterus, there is no trace, in the 
young, after birth, of any umbilical cord; at least Sir E. 
Home could not detect any in the foetus of the kangaroo 
after exclusion *. He has given a representation of a sub- 
stance found in an impregnated uterus +, which he con- 
ceives to be a foetus, in an early stage of formation ; but 
which does not bear the remotest resemblance to the sub- 
ject. From the communications made to hun by Mr Con- 
SIDEN, it appears that the impregnated uterus is filled with 
a gelatinous substance, of a bluish-white colour, in con- 
sistence like half melted glue, and so extremely adhesive as 
to be with difficulty washed off from the fingers. From 
the observations of Mr Bett, which were likewise commu- 
nicated to Sir E. Homer }, it appears that the double ute- 
rus of the wombat is filled, in its impregnated state, with 
the same kind of gelatinous substance which closes up the 
ora tince. ‘ IT made a longitudinal incision into the lar- 
gest of the uteri, and found its coats lined with the same 
jelly met with in its os tinea. Continuing the incision 
through this jelly, and at the same time using gentle 
pressure, there issued a quantity of a thin pellucid fluid, 
accompanied by an embryo wrapped up in very fine mem- 
branes, ‘which contained some of the same transparent 
fluid. The membranes did not appear to be at all connect- 
ed by vessels either to the uterus or gelatinous matter. I 

* Phil. Trans, 1795, p. 233. + Ibid. Table xx. Fig. 2. 
+ Phil. Trans. 1808, p. 309. 
VOL. Ze Ci 
