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XVII. On the Generation of the Marsupial Animals, with a Description of the Impreg- 

 nated Uterus of the Kangaroo. By Richard Owen, Esq., M.R.C.S. and Assistant 

 Conservator of the Museum of the Royal College of Surgeons, London. Commu- 

 nicated by Sir Anthony Carlisle, F.R.S. 



Received January 9, — Read April 24, 1834. 



L HE Marsupiata, or AnimaUa crumenata, as the learned Scaliger designated the 

 few American species which were known in his time, now form in the systems of 

 natural history an extensive series, embracing genera nourished by every variety of 

 food, and exercising in quest of it as many different modes of locomotion as have 

 been observed in other quadrupeds. Their instruments of progression, prehension, and 

 digestion accordingly exhibit corresponding modifications of structure ; while in other 

 parts of their organization peculiarities are found to prevail with a degree of uniformity 

 that justifies the consideration of the 3Iarsupiata as a distinct group oi Mammalia. 



In all the genera of this group the uterus is double, and the true vagina is sepa- 

 rated, either wholly or for a considerable extent, into two lateral canals. Both the 

 digestive and generative tubes terminate within a common cloacal outlet, and the 

 term Monotremata, therefore, though confined to the Edentate Marsupiata, is so far 

 applicable to the whole of this aberrant division. 



As the females approach the Oviparous Vertehrala in their separate genital tubes, so 

 also the males resemble them in the peculiar structure and connexions of the intro- 

 mittent organ ; thus, in the Macropi, the Dasyuri and the Phalangistce, the cor- 

 pora cavernosa penis have the same position below the pubis, with the same want of 

 ligamentous attachment to the bony pelvis ; and the glans has the same bifurcated 

 form and double groove for the transmission of the semen as in the Opossum, in which 

 these peculiarities of the male organs were first accurately described by Cowper*=. 



In those genera in which the females have an inward fold of integument, or abdo- 

 minal pouch, the males have an outward duplicature in the corresponding situation 

 for the lodgement of the testes, which are thus placed anterior to the penis ; and it is 

 a remarkable fact, that the muscle which surrounds the mammary gland in the one 

 sex is analogous to the suspensory cremaster of the testis in the other. 



Both sexes in the marsupial genera manifest also their aflSnity to the oviparous 

 classes in possessing two superior venae cavee, and in the want of the inferior mesen- 

 teric artery : and the marsupial bones, so common in the skeletons of reptiles, are 



* Philosophical Transactions, vol. xxiv. (1704.) p. 1576. 

 MDCCCXXXIV. 2 X 



