194 PROF. DAVID HEPBURN ON THE ANATOMY OF THE WEDDELL SEAL. 
side that their adjacent walls became firmly blended together. This produced the 
appearance of an enlargement common to both of them, but there was no dilatation or 
ampulla on each one. There was no trace of seminal vesicles. 
The penis was constructed on familiar lines. A strong, flexible cylindrical structure 
was present in the body of the penis extending 7 mm. from the base of the glans 
penis backwards. A portion of this structure was removed for microscopical examin- 
ation. In transverse section it presented a circular outline, and was equally associated 
with the two corpora cavernosa penis. Its resistance to the knife suggested young 
bony tissue, and accordingly it was decalcified. Afterwards sections were cut out of 
paratin, mounted, and stained in hematoxylin and eosin. Under the microscope it 
presented the distinctive characters of cancellated bone, being more spongy towards the 
centre of the section and denser towards the surface, where it was closely enveloped in 
a fibro-vascular sheet of membrane, comparable to periosteum. Numerous bone-cells 
were embedded in the developing processes of bone. No trace of hyaline cartilage could 
be detected. No doubt this short cylindrical piece of young bone is comparable to the 
much larger os penis of the walrus, as well as to the furrow-shaped and partly bilateral 
os penis of the fox and the dog. The bulb on each corpus cavernosum penis was situated 
in relation to the crus penis, and not on the penile portion of the organ. From the region 
between the bulb of the corpus spongiosum penis and the rectum, 7.e. corresponding to 
the central point of the perineum, there were two parallel bands of tissue running forwards 
towards the distal end of the body of the penis. These were similar to muscular bands 
which I have elsewhere* described in connection with the penis of the porpoise. 
Probably these act as retractors of the penis. As in the case of the porpoise, a 
microscopic examination of sections cut longitudinally and stained after Van Giesen’s 
method revealed unstriped muscular fibres, with fibrous tissue bundles. Since there 
is no scrotum in the porpoise, whose testes are situated intra-abdominal, and since in the 
seal under consideration each testis occupied a recess placed under the integumentary 
layers in relation to the inner side of the head of the tibia, it seems not unfair to 
consider these non-striped muscular bands as being homologous to the tunica dartos 
layer of an ordinary scrotum, more especially as the muscular fibres of the tunica 
dartos are of the unstriped or involuntary variety. 
* “The Anatomy of the Genito-urinary Apparatus of the adult male Porpoise,’” HapBuRN and WatTErRsToN, Trans, 
Royal Physical Society, Hdinburgh, 1902. 
