400 
The circumstances which first attract atten- 
tion in these singular objects are the total ab- 
sence of hair,* the soft flexible condition of 
the mandibles, and the shortness of these parts 
in proportion to their breadth as compared with 
those of the adult. 
The integument 
with which the man- 
dibles are covered 
is thinner than that 
which covers the rest 
of the body, and 
smoother, present- 
ing under the lens a 
minutely granulated 
surface when the 
cuticle is removed, Head of young Ornithorhyn- 
which, however, is hus. (Owen, Zool. Trans. ) 
extremely thin, and has none of the horny 
character which the claws at this period present. 
The margins of the upper beak are rounded, 
smooth, thick, and fleshy; the whole of the 
under mandible (fig. 196, g) is flexible, and 
bends down upon the neck when the mouth 
is attempted to be opened. The tongue, 
(fig. 196, h,) which in the adult is lodged 
far back in the mouth, advances in the 
young animal close to the end of the lower 
mandible; all the increase of the jaws beyond 
the tip of the tongue, which in the adult gives 
rise to a form of the mouth so ill calculated for 
suction or application to a flattened surface, is 
peculiar to that period, and consequently forms 
no argument against the fitness of the animal 
to receive the mammary secretion at an earlier 
stage of existence. The breadth of the tongue 
in the larger of the young specimens was 3$ 
lines ; in the adult it is only one line broader ; 
and this disproportionate development is plainly 
indicative of the importance of the organ to the 
young animal, both in receiving and swallow- 
ing its food. The mandibles are surrounded 
at their base by a thin fold of integument, which 
extends the angle of the mouth from the base 
of the lower jaw to equal the breadth of the 
base of the upper one, and must increase the 
facility for receiving the milk ejected from the 
mammary areola of the mother. The oblique 
lines which characterize the sides of the lower 
mandible in the adult were faintly visible on 
the corresponding parts of the same jaw of the 
young animal: a minute ridge of the inner 
sides of these lines indicates the situations of 
the anterior horny teeth of the adult. 
The situation of the exterior nostrils (figs. 
195, 196, a) has already been given; they 
communicate with the mouth by the foramina 
incisiva, which are situated at nearly three lines 
distance from the end of the upper mandible, 
and are each guarded by a membranous fold 
extending from their anterior margin: the nasal 
cavity then extends backwards, and terminates 
immediately above the larynx, the tip of the 
Fig. 196. 
« b 
* This is not accidental, as in many of the adult 
specimens sent over in spirit, for the cuticle is 
entire. In the specimens which Mr. G. Sennett 
discovered, the skin had a slight downy appear- 
ance. 
MONOTREMATA. 
epiglottis extending into it, and resting upon 
the soft palate. 
On the middle line of the upper mandible 
and a little anterior to the ils there is a 
minute fleshy eminence lodged in a slight de- 
pression (fig.196, b). In the smaller specimen 
this is surrounded by a discontinuous margin 
of the epidermis, with which substance, there- 
fore, and probably (from the circumstance of 
its being shed) thickened or horny, the caruncle 
had been covered. It is a structure of which 
the upper mandible of the adult presents no 
trace, and is obviously analogous to tho heme 
knob which is observed on the upper 
in the foetus of aquatic and gallinaceous Birds. 
I do not, however, conceive that this structure 
is necessarily indicative of the mandible’s 
having been applied, under the same cireum- 
stances, to overcome a resistance of precisely the 
same kind as that for which it is desi in the 
young Birds which possess it. The shell-break- 
ing knob is found in only a part of the class; 
and although the similar caruncle in the Orni- 
thorhynchus affords a curious additional affinity 
to the Aves altrices, yet, as all the known history 
of the ovum points strongly to its ovo-vivipa- 
rous development, the balance of evi is 
still in favour of the young being brought forth 
alive. 
The situation of the eyes (fig. 195, b, 196, c) 
was indicated by the convergence of a few wrin- 
kles to one point; but when, even in the larger 
of the two specimens, these were ab ges upon the © 
stretch, the integument was found entire, and 
completely shrouding or covering the eyeball 
anteriorly. This fact is one of great im 
to the question of the mammiferous 
of the Ornithorhynchus. For on the supposition 
of the young animal ing locomotive 
faculties, which would enable it like the young 
gosling, immediately after birth or exclusion, 
to follow the parent in the water, and there 
to receive its nutriment, (whether mucous or 
otherwise,*) the sense of vision ought certainly 
* Geoffroy St. Hilaire ae in 1833, for 
the analogy of the abdominal glands of the Orni- 
thorhynchus with those‘of the S 7 ie 
** a mucus possessing a ve we , s, 
“‘T should not be sarees if this mucus, a 
abundant and more substantial in the M 
became the nutriment of the young after their 
hatching. The Monotremata would act, in this 
respect, like some aquatic birds which condact 
their young after hatching to the water, and assist 
them in their sustentation. The maternal instinct 
would lead the female Ornithorhynchus to effect 
the contraction of the gland, which is possible by 
the efforts of the panniculus carnosus and the great 
oblique muscle, between the fibres of which the 
gland is seated, and thus procure for the young, 
at several periods of the day, by wa of uate 
ment, an abundant supply of mucus. if this edu- 
cation is carried on in the water, where we know, 
by the history of the generation of frogs and the 
nutrition of their tadpoles, that the mucus com- 
bines with the ambient medium, becomes thick, 
and supplies an excellent nutriment for the early 
age ae these reptiles, we shall understand the 
utility of the ventral glands of the Ornithorhyn- 
chus, as furnishing a source of nutriment for the 
young of these animals,—for youn i newly 
hatched.””"— Gazette Médicale, Feb. 18th, 1833.— — 
Proceedings Zool, Society, March 1833, p. 29. 
