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of the Oviviviparous Shark, &c. 
In the opossum tribe, and all the pouched animals in New 
South Wales, there is a peculiarity in the form of the female 
organs of generation, which has not been understood ; this is 
a communication between the uterus and vagina during the 
formation of the embryo, by means of one or two lateral 
canals. These I described in my account of the female organs 
of generation of the Kanguroo, and was led to believe, from 
the coagulated state of the parts, which had been a year pre- 
served in spirit, that the openings into the vagina were closed ; 
but this mistake was afterwards corrected in my account of 
the Wombat, in which I stated from Mr. Bell, who examined 
the uterus with the embryo in it, “ On opening the vagina, it 
was found to terminate at the common neck of the uteri ; on 
each side of which, were the openings of the lateral canals, 
and in the middle between them, the meatus urinarius, with 
a slender fleshy pedicle on each side of it. Behind the meatus 
urinarius, were two orifices leading to the uteri, but they 
were filled with a thick gelatinous substance, which rendered 
them completely impervious/'’ These lateral canals enlarge 
very much, as the embryo begins to form ; at one end they 
open freely into the uterus, and at the other into the vagina; 
they are distended with jelly, and are employed to keep up a 
communication with the external air, for the purpose of 
aerating the foetal blood ; their appearance in the kanguroo 
is seen in the annexed drawing. 
As the embryo in all the animals of this tribe is contained 
in a soft egg, which, from the description of Mr. Bell, the 
only person who has attentively examined it, has no connec- 
tion with the internal membrane of the uterus, some apparatus 
like the lateral canals became necessary for the aeration of 
Ff 2 
