392 
Male organs, Ornithorhynchus. (Mechel. ) 
The Monotremes are true testiconda, and in 
this respect differ from the Marsupial animals. 
In the Echidna each testicle is situated imme- 
diately below, or sacrad of, the kidney, and is 
suspended to that gland bya fold of peritoneum ; 
the same fold is continued to the neck of the 
bladder, inclosing the vas deferens, which is 
disposed in a szries of close transverse folds 
throughout its whole course. It corresponds 
closely, in these respects, with the Ornitho- 
rhynchus. In neither Monotreme is there any 
disparity of size between the right and left 
testicle : the latter is figured in situ at a’, fig.187. 
The vas deferens ( fig.190, f.) emerges from the 
upper or atlanta! extremity of the testis (e) ; 
aA, from its peculiarly extended, plicated, or 
folded course, seems to prolong the epididymis 
nearly to the neck of the bladder; the folds 
gradually diminish, and the duct itself enlarges, 
as it approaches its termination, which is in the 
beginning of the urogenital canal (g). This 
canal is continued through the pelvis and termi- 
nates in the vestibular passage, anterior to the 
orifice of the rectum (q). 
The vascular tissue of the penis com- 
mences at the termination of the urogenital 
canal; it is separated by a median septum 
into two lateral moieties, and both are in- 
closed by a common dense fibrous sheath. 
The whole penis in its collapsed and retracted 
state is about fifteen lines in length, and is con- 
cealed in a large preputial sheath. The ter- 
minal half of the penis is formed by the glans, 
which presents a quadrilateral form, and is 
traversed by a median longitudinal furrow upon 
both the upper and the under surface. Its ex- 
terior is beset with numerous short and hard 
epidermal spines: its extremity is bifurcated, 
and each lobe is directed outwards and termi- 
MONOTREMATA. 
nates in three or four spines, (k, k,) much 
larger, but softer, than the rest, and which are 
usually retracted in a depression. ; 
A fongitadinal azygos levator muscle runs 
along the upper surface of the penis; it arises 
by two lateral slips from the mternal stratum 
(n) of the protrusive sphincter. Another lon- 
gitudinal but longer and more slender muscle, 
the retractor penis, (fig. 190, p,) arises from 
the upper part of the of the tail, bends 
downwards over the caudal muscles and vessels, 
and is inserted into the origin of the penis near 
the termination of the urogenital canal. The 
true urethra or canal of the penis begins bya 
small orifice at the root of hs penis, — the 
termination of the urogenital passage, 
the combined action of the last described 
muscle with the sphincter cloace, it can be 
brought into closer approximation with the uro- 
genital It must be supposed that 
this temporary continuation of the urethra and 
urogenital takes place during the vigo- 
rous muscular and vascular actions of the parts 
in coitu, and that the semen is then propelled 
from the one along the other without i 
into the common vestibular compartment of the 
cloaca. Under ordinary circumstances, as 
when the urine is transmitted along the uro- 
genital passage, it must escape into the vesti- 
bule, and may there be blended, as in the Bird, 
with the rectal excrement. The true seminal 
urethra, commencing by the distinct ape 
as above described, is about a line in diameter, 
and continues single to the middle of the glans, 
where it divides into two canals; each branch 
runs along the middle of the bifurcation of the 
glans, and, when arrived at the base of the large 
papille, subdivides into smaller channels cor- 
responding with the number of the papille, 
and opening upon their apices. If the canal 
of the penis were slit open along its under part 
and thus converted into a groove, the male 
organs of the Ornithorhynchus would be then 
essentially like those of a Tortoise. The adhe- — 
sion to the Mammalian type is manifested ina 
highly interesting manner by the com 
of the urethral canal, whilst the affinity to the 
Marsupial order is evinced in its bifurcation ; 
corresponding with that of the glans itself. Had 
the penis been neither perforated nor } 
as Cuvier once believed, the structure wou 
have been extremely anomalous. That the 
existence of a penis is essentially and subordi- 
nately related to the sexual organs and not to the — 
renal, is beautifully illustrated by the complete — 
separation of the uro-urethral from the semino- — 
urethral passages in the Monotremata. 
The modifications by which the male 
in the Echidna din a ae of the Ornithor- 
hynchus, are confined to the glans penis, which 
divides into four mammiloid processes, rough- 
ened by minute papille, and terminated by a 
depression in which is the branch of the semi-— 
nal canal that traverses each process. o7 
glands (fig.180, k, k, and fig.190, A) are of larg 
relative size; they are situated between the be 
of the penis, the arch of the ischium, and intern 
= of the thigh: their secretion is ied 
y along and slender duct (fig. 190, m) into the 
