MAMMALIA. 
53 
they commence with the growth or enlargement of the mammary glands pre- 
liminary to birth, and probably increase in size with the growth of the young ; 
but it is very doubtful whether they increase ever so much as to include or 
wholly conceal the young animal. 
No such structure has ever been found in Ornithorhynclms ; nor is it likely 
that this animal, compelled to seek its food in water, could safely carry its 
progeny during such quest. 
The author describes the mammary glands and the urogenital organs of the 
female Echidna, and its foetus ; in the latter he notices, beside a scarcely vi- 
sible trace of an umbilicus, especially an internarial tubercle which he pre- 
viously observed in the foetal Ornithorhynclms, and which is obviously homo- 
logous with the hard knob on the upper mandible of chelonians and birds, by 
which they break their way through the covering of the egg. 
And, indeed, from the latest accounts sent to the author from Australia, it 
would appear that the question of the Monotremates being viviparous or ovo- 
viviparous is far from being settled. 
The memoir is accompanied by three plates showing the 
female with the foetus in situ, the mammary glands and genital 
organs, and various views of the embryonal Echidna and 
Ornithorhynclms. 
Echidna hystrix. Mr. Kretft observes that, strange as it may appear, the 
Echidna probably lives on grass, as the intestines of several specimens were 
found to be full of digested grass or herbs. On the Vertebr. of the Lower 
Murray, p. 23. 
