. Nature . esays, On the middle line of the upper mandible, and alittle anterior to the nostrils, there is a minute fleshyeminence lodged in a slight depression. In the smallerspecimen this is surrounded by a discontinuous margin ofthe epidermis, with which substance therefore, and pro-bably (from the circumstance of its being shed) thickenedor horny, the caruncle had been covered. It is a structureof which the upper mandible of the adult presents notrace, and is obviously analogous to the horny knob whichis observed on the upper mandible in the fcetus of somebirds. I do not, however, conceive
. Nature . esays, On the middle line of the upper mandible, and alittle anterior to the nostrils, there is a minute fleshyeminence lodged in a slight depression. In the smallerspecimen this is surrounded by a discontinuous margin ofthe epidermis, with which substance therefore, and pro-bably (from the circumstance of its being shed) thickenedor horny, the caruncle had been covered. It is a structureof which the upper mandible of the adult presents notrace, and is obviously analogous to the horny knob whichis observed on the upper mandible in the fcetus of somebirds. I do not, however, conceive that this structure isnecessarily indicative of the mandibles having beenapplied, under the same circumstances, to overcome aresistance of precisely the same kind as that for which itis designed in the young birds which possess it. Theshell-breaking knob is found in only a part of the class,and although the similar caruncle in the Ornithorhynchusaffords a curious additional affinity to the Aves, yet as all. the known history of the ovum points strongly to its ovo-viviparous development (see also Phil. Trans., 1834,P- 555); the balance of evidence is still in favour of thistheory. Later still {Phil. Trans., 1865, p. 671) he published apaper on the Marsupial pouches, mammary glands, andmammary fcetus of the Echidna hystrix, wherein heproved that the same caruncle was present in the Echidnafoetus, and further that this was carried about by themother in a pouch (two being present in each individual,one on either side the middle ventral line), into whichopened the mammary glands. Owen adheres firmly to the opinion that the Monotremesare ovo-viviparous, in which opinion he is supported bythe evidence of, amongst others, Sir E. Home {, 1802, p. 67), whose account is probably theearliest notice of any detail, which was published inEngland with regard to the internal anatomy of Home says at the close of his paper, thisanimal having no nipples and no regula
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