to be granted to it in order to direct its move- 
ments. The privation of this sense, on the 
contrary, implies a confinement to the nest, 
and a reception on land of the mammary 
secretion of the parent. 
The auditory orifices (fig. 196, d) are situated 
-about a line behind the eyes. 
The general form of the body and the carti- 
laginous condition of the bones of the extre- 
_ mities equally militate against the young Orni- 
~ thorhynchus possessing, at this period of its 
_ existence, active powers of swimming or creep- 
ing. The head and tail are closely approxi- 
mated on the ventral aspect, requiring force to 
_ pull the body out into a straight line ; and the 
relative quantity of integument on the back and 
belly shows that the position necessary for the 
due progressive motions is unnatural at this 
_ stage of growth. 
____ The toes on each of the four feet were com- 
pletely formed, and terminated by curved, co- 
nical, horny claws; but the natatory fold of 
_ membrane of the fore foot had not the same 
proportional extent as in the adult, and the 
‘spur of the hind foot did not project beyond its 
_ socket in either specimen. In the smaller one, 
which was a male, it presented the form of an 
obtuse papilla; while in the larger specimen, 
_ although a female, it was more plainly developed 
ind more pointed (fig. 197,,f). This circum- 
—, 
oC 
Fig. 197. 
"Hina. fot and spur, young female Ornithorhynchus, 
=. magnified. ( Owen, Zool. Trans. ) 
te 
Stance is inexact accordance with the known laws 
_ of the development of sexual distinctions, espe- 
_ cially of those of secondary importance, such 
as beards, manes, plumes, horns, tusks, spurs, 
&e,, which do not avail in distinguishing the 
sexes till towards the period of puberty. As 
the spur is the only obvious distinction of the 
sexes in the full-grown Ornithorhynchus, I 
_ Was compelled to refer to the internal essential 
_ organs, in order to determine the sex of the 
_ Specimens here described. 
_ The ventral surface of the smaller specimen 
was carefully examined with a lens; but no 
trace of an umbilicus could be satisfactorily 
_ determined. In the very young or newly born 
_ Kangaroo, a longitudinal linear trace of the 
_ attachment of the umbilical vesicle is at that 
__ time apparent, but it is rapidly obliterated ; 
_ aS is probably also the case in the Omitho- 
By tynchus, , 
______In the smaller specimen the intromittent 
n projected a little way beyond the excre- 
VOL. III. 
-MONOTREMATA. 
401 
mentory orifice, as in the young Marsupialia ; 
but it was not continuous, as in them, with the 
anterior margin of that outlet. In the larger 
female specimen the corresponding organ was 
visible just within the verge of the opening ; 
but this clitoris, remaining stationary in its 
development, is afterwards, as 1 have shown in 
my paper on the Mammary Glands of the Mo- 
notremes,* removed to a distance from the 
preputial aperture by the elongation of the 
sheath, just as the minute spur of the female 
lies concealed at the bottom of the progres- 
sively elongated tegumentary socket, and as 
the tongue is left at the back of the oral cavity - 
by the growth of the jaws. 
The following anatomical appearances were 
noticed in these young Ornithorhynchi :— 
On laying open the abdomen in the larger 
specimen, the most prominent viscus was the 
stomach, which was almost as large as in the 
adult animal, deriving at this period no assist- 
ance from the preparatory digestive cavities, 
the cheek-pouches, which were not yet deve- 
loped. The stomach extended in a curved 
direction across the epigastric and down the 
left hypochondriac region to the left iliac re- 
gion. It was full of coagulated milk. 
In the smaller specimen the stomach was 
empty; when distended with air it exhibited 
a less disproportionate development. It was 
situated in the left hypochondriac and lumbar 
regions. The intestines contained air, with 
granular masses of a mucous chyme adhering 
to their internal surface. This condition of 
the digestive canal would seem to show that 
no long period had elapsed since the birth of 
the specimen, and that either lactation had not 
been in full action, or that the young one had 
been deserted by the parent for some time 
before it was taken. 
In both specimens the spleen bore a propor- 
tionate size with the stomach; and as the dif- 
ference in the development of the stomach was 
considerable, the correspondence between the 
condition of the spleen with that of the diges- 
tive cavity was made very obvious. 
The difference in the development of the 
liver was not greater than corresponded with 
the different size and age of the two specimens. 
But the pancreas in both bore the same ratio to 
the stomach as the spleen. This, therefore,would 
seem to afford some indication of the organs 
with which the function of the spleen is more 
immediately related. 
The intestinal canal in the larger specimen 
was situated almost entirely on the right side 
of the abdumen. The c@cum in both was very 
minute and filamentary. I examined the i/eum, 
and more especially in the usual situation above 
the cecum, but could not perceive any trace of © 
the pedicle of the umbilical or vitelline vesicle. 
The other vestiges of foetal organization were 
more obvious than in the ordinary marsupial 
or ovoviviparous Mammalia. 
In both specimens, but more especially im 
the smaller one, the umbilical vein was seen, 
extending from a linear cicatrix of the perito- 
* Phil. Trans. for 1832, p. 525. 
2» 
