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XXII. On the Mammary Glands of the Ornithorhynchus paradoxus. By 
Mr. Richard Owen. Communicated by J. H. Green, Esq. F.R.S. 
Read June 21, 1832. 
T HE extraordinary nature of the monotrematous quadrupeds of Australia 
cannot be illustrated more forcibly than by observing that it is still doubtful 
to what class of animals they properly belong. In the confines of the animal 
kingdom, it is less surprising that a species should occasionally be discovered, 
either so devoid of external character, or of a form so strange, as to occa- 
sion a difficulty in ascertaining its class : and an Entozoon, a Lernsea, or an 
aggregate species of Salpa may require very minute investigation in order to 
determine its relation even to the most comprehensive division of a methodical 
arrangement. But the same difficulty occurring with respect to a hairy 
quadruped, affords one of the most unexpected, as well as interesting pro- 
blems in natural history, and renders acceptable the smallest addition to the 
series of facts already ascertained respecting so anomalous a creature. 
In this country we can hardly hope to throw light upon the economy of 
Ornithorhynchus and Echidna, except by the way of anatomy ; at least, the 
aquatic habits of the former species render it improbable that it will ever be 
brought alive to our menageries. But the same objection does not apply 
to the spiny ant-eater, and it is to this animal therefore that the attention of 
voyagers from New South Wales should be more especially directed with a 
view of importation. 
It is well known that one of the points now at issue with respect to these 
animals, is the nature of certain glandular organs which they possess, which 
are supposed to appertain to the mammary system : and it is obvious that our 
knowledge of the true affinities of the Monotremata greatly depends on a 
complete elucidation of this subject. To it, therefore, my attention has been 
particularly directed whenever an opportunity has occurred of examining the 
Ornithorhynchus paradoxus ; and I have invariably noted the condition of 
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