312 
but in this circumstance we may perceive an 
example of the retention of a typical structure 
at the deeper seated part of a system of organs, 
when not incompatible with a slight modifi- 
cation of a peripheral segment of the same 
system ; it being by no means obviously neces- 
sary to abrogate the division of the urethral 
bulb simply because the blood accumulated 
in each division was to be driven in a concen- 
trated current upon a single, instead of a dou- 
ble glans penis. 
e intermediate structures of the glans be- 
tween the two extremes above instanced are 
resented by the Ursine Dasyure, Koala, and 
ombat. In the Koala (fig.135, B) the glans 
penis terminates in two semicircular lobes, and 
the urethra is continued by a bifurcated groove 
along the mesial surface of each lobe. In the 
Wombat (fig. 135, C) there isasimilarexpansion 
ofthe urethra into two divergent terminal grooves, 
but the glans is larger, cylindrical, and par- 
tially divided into four lobes:* the chief’ struc- 
ture of interest in this part of the Wombat is 
the callous external membrane of the glans, 
and its armature of small recurved, scattered 
horny spines, which do not occur in any other 
Marsupial animal. The small retroverted pa- 
ille on the infundibuliform glans of the 
oala and on the bifurcate glans of the Phalan- 
gers and Petaurists are not horny. 
In the Perameles lagotis not only is the glans 
bifurcate, but each division is perforated, and 
the urethral canal is divided by a vertical 
septum for about half an inch before it reaches 
the forked glans. From theseptum tothe bladder 
the canal is simple, as in other Marsupials. 
The bifurcations of the glans in the Opossums 
and Phalangers are simply grooved. 
If the experiments of Haighton and the 
detection, by Drs. Bischoff and Barry, of sper- 
matozoa upon the ovary itself a coitus, 
had not rendered the question of the neces- 
sity of the contact of the semen with the 
ovarium for impregnation almost independent 
of the aid of Comparative Anatomy, the diffe- 
rences of structure above described in the 
urethra and glans penis of the Marsupial 
animals would have gone far to explode the 
once prevalent notion of an ‘ aura seminalis’ 
fertilizmg the ovum through the medium of 
the circulating fluid: for why, on such an 
hypothesis, should the impregnation of two 
ovaria, each communicating with a distinct 
oviduct, uterus, and vagina, as in the Opos- 
sum, require two conduits of the semen in the 
male, one for each vagina?—and wherefore, 
in the case of an uniparous Marsupial, in 
which the fecundating stream need ascend only 
to a single ovarium, as in the Kangaroos and 
ted ian is the penis terminated by a single 
Jans 
‘ The spermatozoa of the Perameles have a 
single barb at the base of the head, which is 
sub-elongate and compressed ; in other respects, 
as in size and proportion of the filamentary tail, 
they resemble the spermatozoa of the Rabbit. 
: Nan Legons d’Anat. Comparée, 1805, t. vy. 
p- 9i. 
MARSUPIALIA. 
Neither Je be Kangaroo, Phalanger, nor Da- 
ure did t NR present a spiral head 
ns any noticeable deviation from the char oters 
of the spermatozoa in the smaller placental 
quadrupeds: those of the Dasyure have 
node at the base of the head. oil 
The corpus cavernosum penis commences b 
two crura(d, d, figs. 135, 136), neither of whi 
have any immediate attachment tothe bony pelvis 
Cuvier correctly states, that in the Kangaroo the 
two crura of the corpus cavernosum, and the tw 
bulbs of the corpus spongiosum, soon unite to 
form a single cylindrical body, having a cana 
which nearly follows the direction of its axi 
whose parietes are equally strong and fibrous, 
and which contains the urethra; so that the 
transverse section of the corpus cavernosum 
resembles a ring; but the two lateral cavities 
are separated by two vertical septa which e: 
tend one from the central canal to the dorsum 
penis, the other from the central canal to the 
inferior wall of the penis.* 
In the Kangaroo and Potoroo, the erectores 
penis (fig. 135 d,d) arise by a thin fascia from 
near the lower part of the symphysis pubis, soon 
become fleshy, and increase in thickness as they 
pass outwards: each muscle then returns upor 
itself, atan acute bend, to grasp the crus pe 
and terminates in a strong tendinous expan 
at the junction of the cavernous with 
bous structure. 
Fig. 136. 
Male Organs, 
( Cowper, l. c.) 
The retractor penis (figs 135,136, g, g) arises 
in the pasta gp al middle ee the sa- 
crum, and divides into two muscles, behind 
rectum, opposite the dilated commencer 
of the musculo-prostatic part of the w 
each division diverges to the side of the ree 
then passes to the interspace between the 
tum and roots of the penis, and along the 
¢ 
oe 
_™ Legons d’Anat. Comp. 1805, t. v. p. 73. 
