OF THE ORNITHORHYNCHUS PARADOXUS. 
529 
inner membrane, which possesses in a high degree the character of a secreting 
membrane. This membrane at the cervix uteri presented in all the speci- 
mens many deep and close-set furrows, which as the canal grew wider were 
gradually lost, and the surface became more or less smooth in the different 
specimens, being most irregular in the specimen with the largest ovary : in 
the contracted part of the tube, the inner surface is at first smooth, but beyond 
that becomes finely reticulate, and in the terminal dilated part is again smooth. 
The laminae at the cervix uteri, when seen from the urethro-sexual cavity pro- 
jecting across the terminal orifice, give the appearance of that orifice being 
divided by a septum. But in whatever way I have examined this part, I have 
never been able to detect such a division ; the uterine tubes have invariably 
presented only a single aperture of communication with the urethro-sexual 
cavity. Such a septum may, however, exist in the virgin state of the parts ; 
and on their assuming the natural functions, it may, like the hymen, be obli- 
terated. Professor Geoffroy, who has described and represented this struc- 
ture, (Mem. du Museum, xv. p. 32. PI. I.) regards it as a rudimentary indica- 
tion of the form of uterus peculiar to the Marsupiata. 
In all the specimens but one, the ovary existed only on the left side ; it is 
appended to the portion of ligament* before mentioned, and is of a flattened 
oblong form. In the specimen in which the mammary glands presented the 
smallest size (Plate XV.), the left ovary consisted of a thin, smooth, and soft 
substance, measuring half an inch in length, three lines in breadth, and half 
a line in thickness ; the external covering was a tough membrane, beneath 
which were two black specks, but there was no appearance of ova ; the rest 
of the substance being cellular membrane only. In the specimen (PI. XVI.) in 
which the mammary gland was a little more advanced than the preceding, the 
left ovary presented the highest observed degree of development ; and the right 
ovary was more distinct than in any of the other specimens. The left ovary 
was nine lines in length, five in breadth, and from two to three in thickness, 
having numerous ova distinctly developed in it, two of which were two lines 
and a half in diameter ; and therefore, probably, not less than those which 
Mr. Hill has described'!' as being the size of small peas. These consisted of 
* This ligament is represented in Mr. Bauer’s magnified drawing of the posterior view of the 
ovary of the Ornithorhynchus, Phil. Trans. 1819, PI. XVIII. p. 240. 
t Linn. Trans, vol. xiii. p. 623. 
