402 MONOTREMATA. a 
neum, opposite the middle of the abdomen, 
along the anterior margin of the suspensory 
ligament to the liver. It was reduced to a 
mere filamentary tube, filled with coagulum. 
From the same cicatrix the remains of the 
umbilical arteries extending downwards, and 
near the urinary bladder, were contained within 
a duplicature of peritoneum, having between 
them a small flattened oval vesicle, the re- 
mains of an allantois, which was attached by 
a contracted pedicle to the fundus of the 
bladder. 
As both the embryo of the Bird and that of 
the ovoviviparous Reptile have an allantois 
and umbilical vessels developed, no certain 
inference can be drawn from the above appear- 
ances as to the oviparous or viviparous na- 
ture of the generation of the Ornithorhynchus, 
But the structure of the ovary and that of the 
ovum, both before and after it has quitted the 
ovisac, afford the strongest analogical proof of 
the intra-uterine developement of the embryo, 
and at the same time accord with the ascer- 
tained fact of the mammary nourishment of the 
young animal. 
The kidneys were situated remote from th 
pelvis and high up in the lumbar region. 
The situation of the kidneys with respect to 
each other varied in the two specimens; in the 
larger one, the left was a little higher than the 
right; in the smaller one it was a little lower; 
the latter is the ordinary position in the adult. 
The supra-renal glands did not correspond with 
this arrangement, but in both instances the 
right was higher than the left, agreeing with the 
relative position of the testes in the male, and 
the ovaries in the female. In Man the large 
size of the supra-renal glands is noted as a 
foetal peculiarity, but in the Ornithorhynchus 
they are of minute size, their greatest diameter 
not exceeding one-eighth of a line in the smaller 
specimen here described ; and they increase in 
size progressively with the growth of the ani- 
mal, and in a greater proportion than the kid- 
neys, which increase would appear, therefore, 
to have relation to the development of the ge- 
nerative organs. There were no traces of the 
corpora Wolffiana. 
he testes in the small male specimen were 
situated a little below the kidneys: they were 
of an elongated form, pointed at both ends, with 
the epididymis folded down, as it were, upon 
their anterior surface. In the female, the ova- 
ries were freely suspended to the loins in a 
similar position, the right being at this period 
as large as the left: it is the persistence of the 
latter at an early stage of development which 
occasions the disproportionate size of the two 
glands in the adult. The still greater inequa- 
lity of size in the oviducts of the Bird arises, 
as is well known, from a similar arrest of the 
development of the one on the right side, but 
both are equal at an early stage of existence. 
The uteri were straight linear tubes, scarcely 
exceeding the size of the ovarian ligaments. 
The lungs were found amply developed in 
both specimens; the air-cells remarkably ob- 
vious, so as to give a reticulate appearance to 
the surface, and a resemblance to the lungs of 
ordinary Marsupialia in having the thymus 
a turtle. They had evidently been permeated — 
by air in the smaller specimen. “SI 
The heart, in both specimens, was of the — 
adult form, with the apex entire; but the left 
auricle was proportionately larger than in the 
adult heart. 
true viviparous Mammalia. Here also we * 
have the indication of a more prluestes bi 
existence than in the marsupial animals, there 
being no trace of a ductus arteriosus either in — 
The Ornithorhynchus also deviates from the — 
—_. 
gland. This is situated in front of the great 
vessels of the heart, and consists of two lobes, 
of which the right is the largest. The traces of 
foetal structures presented by these young Or- 
nithorhynchi, and especially the allantoic dila- 
tation of the urachus, indicate that the Mono- 
tremata differ from the Marsupialia ao 7 
continuance of the true fetal or im 
existence. ae 
Mammary organs.—In this section will be 
adduced the evidence in f of the ially 
Mammalian nature of the Monotremes which 
the presence and ascertained function of the — 
mammary glands have yielded. : 
The most important result of Professor Mec- _ 
kel’s anatomical investigations of the Ornitho- 
rhynchus was his discovery of the two large 
abdominal subcutaneous glands: these he con- 
cluded to be the mammary o which until 
that period had been sup to be absent in — 
the Ornithorhynchus. ’ 1 
Subjoined is the figure which Meckel has — 
given of one of these glands in its natural — 
relative position, fig. 198. It measured four — 
inches and a half in length, two inches in — 
breadth, and half an inch in thickness. j 
From this apparently conclusive evidence of — 
the affinity of the Ornithorhynchus to the Mam=- — 
malia, Professor Meckel, however, is far from 
drawing conclusions as to the identity of their 
mode of generation. For assuming that the 
difference between the bringing forth of living — 
young and of eggs is really very small and by 
no means of an essential nature, and remarking: 
that birds have accidentally hatched the eg 
within the abdomen and so produced a livit 
foetus,—an occurrence which has also beer 
duced by direct experiment, and that, las 
the generation of the Marsupial animals is very 
similar to the oviparous mode, he deems it 
very probable that as the Ornithorhynchus: 
proaches still nearer than the Marsupial ani 
mals to Birds and Reptiles, its mode of gene- 
ration may be in a prope degree analo- 
gous. For an animal possessing mammar 
glands he claims, however, the right to ra 
with the Mammalia, agreeing with Professor 
Geoffroy only so far as to consider the Mor 
tremata as a distinct order of quadrupe 
which he places, as Cuvier has done, next 
the Edentata. ae 
Against this conclusion, however, Profess 
