556 ~ MR. OWEN ON THE OVA OF THE ORNITHORHYNCHUS PARADOXUS. 



ovary of the Ornithorhynchus, with a view to determine its exact relations with that 

 of the normal Mammalia, I believe myself in no way biassed by the proof of the 

 mammiferous nature of the Ornithorhynchus, which has been afforded by the con- 

 current testimonies of several scientific observers who have themselves witnessed 

 the lacteal secretion ; since it is obvious that in order for the milk, the elaboration 

 of which is determined by the derivation of blood from the generative system, to 

 meet with a due recipient after the cessation of the uterine functions, it is only neces- 

 sary that the offspring should possess the capability of receiving the maternal secre- 

 tion, and not that it should have gained that power by any particular mode of deve- 

 lopment, or through the agency of any given system of vessels. 



From an examination of the internal structure of the mammary foetus of the mar- 

 supial animals, there appeared, indeed, previously to the present inquiry, to be 

 grounds for entertaining a belief that lactation might coexist with a mode of gene- 

 ration essentially similar to that of the Viper and Salamander; and a subsequent exa- 

 mination of the uterine foetus in the Kangaroo has gone far to establish the truth of 

 this supposition*. 



In the specimen of the female organs of the Ornithorhynchus figured in Plates XVI. 

 and XVII. of the Philosophical Transactions for 1832, two ovisacs, or Graafian fol- 

 licles, had taken on the action of preparation for the male influence ; and, it is pro- 

 bable, from a comparison of these ovisacs with the corpora lutea of specimens here- 

 after to be described, in which the ova had recently passed into the uterus, that they 

 had nearly if not quite attained their full development. This opinion is further 

 corroborated by the circumstance of the uterus to which the ovisacs in question be- 

 longed having increased almost to the size of that of the impregnated female figured 

 at Plate XXV. fig. 2. in illustration of the present communication. In a female 



* Latbeille, in his Families Naturelles du R^gne Animal, 8vo, 1825, excludes the Monotremata from the 

 Mammiferous series, at the conclusion of which he observes, " tous ceux dont nous traiterons desormais sont 

 ovipares ou ovovipares, et par consequent depourvus de mamelles." (p. 66.) Aristotle says, " No oviparous 

 animal has an epiglottis :" and there are perhaps few generalizations in the Historia Animalium that testify- 

 more strongly to the extent of his anatomical researches. This remarkable proposition has stood the test of 

 ages of subsequent research, and is adopted by Cuvier without any modification in the Rfegne Animal (Nouv. 

 Ed. tom. i. p. 300.) ; yet it must always have been difficult to suppose that the relation which subsisted be- 

 tween a small part of the larynx and any given mode of generation could be other than that of simple coinci- 

 dence ; and it now appears that, in the sense in which Cuvier defines oviparous generation (Ibid. p. 300.), 

 the Marsupiata do form an exception to the Aristotelian rule. The Ornithorhynchus also possesses a large 

 and well-formed epiglottis, and it certainly has mammary glands. From this we may be led to conclude that 

 an epiglottis is formed not because the foetus is developed by a placenta, but because it is to be nourished after 

 birth by a lacteal secretion. The larynx requires, at that feeble jieriod, an extraordinary protection, for which 

 the young bird or reptile has no need : and it is worthy of remark, that the epiglottis is proportionately deve- 

 loped as the young mammal is prematurely born. Having therefore, as its peculiar coexistence with lactation 

 would show, an especial reference to the earlier periods of life, we can better understand why the epiglottis 

 should be of secondary importance to the adult, in which both accident and experiment have shown that it is 

 not essential to safe deglutition. 



