682 PEOEBSSOB OWEN OK TSE UAXStTPIAL I'oiTilIvs, maaimauy glands, 
The urogenital canaJ is 1 inch 4 lines in length, and about 9 linos in diameter: its 
inner surface shows by some coarse wavy longitudinal ragffi its capacity for dilatation. 
The rectum was here of great width; it terminated by a contracted puckered aper- 
ture (W)j in the back part/of the beginning of the vestibule, behind the aperture of com- 
munication of the urogenital with the vestibular canal. The distal half of the vesti- 
bule is lined by a denser and less \;iscular epithelium than the proximal one. 
I conclude from thfese appearances thai the present Echidna had produced two young, 
of which one only was secured; and that, either, one was left in a. nest in the fallen 
hollow free, while the other was imbibing milk from the pouch; or that, if she had 
ctnied a mammary lo tus in each pouch prior to her capture, one had fallen out in the 
SCUiSe thai drove her Grom her place of shelter and concealment. The slight difference 
in size between the right and Left mammary glands may relate to the Longer continuance 
of the left one in functional activity, after the loss of the young from the right pouch. 
The chief points in the generative economy of the Monotremes which still remain to 
be determined by actual observation are — 
I . The manner of copulation, 
li. The season of copulation. 
3, The period of gestation. 
I. The nature and succession of the temporary structures for the nourishment and 
respiration of the firtus prior to birth or exclusion. 
6. The size, condition, and powers of the young at the time of birth or exclusion. 
6, The period during which the young requires the Lacteal nourishment. 
7. The age al which the animal attains its lull size. 
In respect to the second point: as Mr. Harris caught the female Echidna with the 
young, about an bach in Length, on the L2th of August, she may be impregnated at the 
latter end of June or in July. Females Killed in the last week of Julj and the first 
week of August, in the Province of Victoria, would be most, likely to afford the capital 
facts noted under the fourth head; viz. the impregnated ovum in utero showing some 
tage of embryonal development W the spiny terrestrial Monotrenie. As to the hairy 
ami aquatic Ornithovhynchus^ the Impregnated females in which ova were found in the 
uterus, of small size, and prior to the formation of the embryo, were caught on the 6th 
and 7th of October*. Young Ontif/ior/if/ttc/i/, measuring in length in a straight line 
1 inch and £ths, were found in the nest on the 8th of December, The period of im- 
pregnation is, therefore, in this species, in the locality of the Muirumbidgce River, 
probably the latter end of September or beginning of October. Females captured in 
the latter half of October and in the month of November, would be most likely to have 
ova in utero exhibiting stages of embryonal development. 
On this point I have been favoured with the following letter, one of a kind including 
01001 which reach me from Australia on the subject, exciting, instead of allaying, 
curiosity. 
• Sit ligmv of the i in j • r< ut e< 1 specimen in Philosophical Transw tinii*, 1834, Plate XXV. a, a'. 
