66 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 

 paraffin, mounted, and stained in hrematoxylin 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 spougiosurn penis and the rectum, i.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," HEPBURN and WATERSTON, Trans. 

 Royal Physical Society, Edinburgh, 1902. 



(ROY. SOC. EDIN. TRANS., VOL. SLVIII., 194.) 



