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XXV. On the Young of the Ornithorhynchus paradoxus, Blum. By Ricuarp Owen, 
Esq., F.Z.S., Assistant Conservator of the Museum of the Royal College of Surgeons 
in London. 
Communicated May 27, 1834. 
IT must be gratifying to every friend of Natural History to perceive how rapidly, by 
the exertions of enlightened travellers, the different facts and materials are accumu- 
lating which tend towards the complete elucidation of the economy and natural affini- 
ties of the Monotrematous Quadrupeds. 
On a retrospect of the history of these anomalous animals, we find in the year 1829 
the sum of what was then certainly known as to their generative function thus expressed 
by Cuvier: ‘‘ Comme enfin on n’est pas encore unanime sur l’existence de leurs ma- 
melles, on en est a savoir si ces animaux sont vivipares! ou ovipares.”2 Such was the 
condition in which this question was left, notwithstanding the valuable labours of 
Meckel and M. Geoffroy, and such the received opinion as to the essential nature of 
the connexion between lactation and placental generation. 
It appears to have been under this impression that the revival of Meckel’s doc- 
trine in 1832 was, on the one hand, regarded, though erroneously, as proof of the vivi- 
parous generation of the Ornithorhynchus?, and on the other hand, as strenuously opposed 
by those Naturalists who had adopted the oviparous theory, and who regarded the Mo- 
notremata as a distinct class of Vertebrata. The true theory will in all probability be 
found somewhere between these extremes. Of all known Mammalia, the Edentulous 
Marsupiata undoubtedly approximate most closely the oviparous type. But if we except 
the partial atrophy of the right moiety of the female organs, and the form of the mouth 
of the Ornithorhynchus, all the principal deviations from the mammiferous type, as ex- 
hibited in the skeleton and in the composition of the entire generative apparatus, indi- 
cate the affinity of the Monotremata to the Reptilia rather than to the Aves ; and all 
the well ascertained facts respecting their generation support the inference, that, as in 
many Reptiles, the germ is developed within the body of the parent unaided by the for- 
mation of a placenta. 
1 That there might be no mistake as to the sense in which this word is used, Cuvier previously defines it. 
«Dans tous les Mammiféres la génération est essentiellement vivipare ; c’est 4 dire que le foetus, immédiatement 
aprés la conception, descend dans la matrice, enfermé dans ses enveloppes, dont la plus extérieure est nommée 
chorion, et V'intérieure amnios ; il se fixe aux parois de cette cavité par un ov plusieurs plexus de vaisseaux, 
appelés placenta, qui établissent entre lui et sa mére une communication, d’oi il tire sa nourriture, et probable- 
ment aussi son oxygénation.”—Régne Animal, tom. i. p. 64. 2 Ibid., p. 234. 
2a2 
