40 



least likely, in the modifications of these organs, to mistake a merely 

 adaptive for an essential character. The true Cetacea, as is well 

 known, have no trace of vesiculce seminales ; but I found these bags 

 present and of large size in the male specimen of our Dugongs. 

 These accessory secerning vesicles measured each four inches in 

 length, and two inches in diameter at their fundus, where they were 

 widest, and their glandular parietes thickest. The internal surface 

 of the remainder of the cavity was reticulated. The vasa deferentia 

 are short, and disposed in irregular convolutions. Each cms penis 

 was attached to the lower expanded extremity of the ischia, which 

 were anchylosed to the ilia on each side*. Iiithe true Cetacea the 

 retractores penis run along the sides to the under surface of the pe- 

 nis ; while in the Dugong the corresponding muscles are inserted 

 into the dorsum penis, as in the elephant : they meet and join in a 

 strong tendon half way between the cms and the glans jienis. In 

 the true Cetacea the body of the penis consists of a single corpus ca- 

 vernosum, grooved above for the passage of the vena dorsalis, and 

 more deeply excavated below for the lodgement of the urethra and 

 its surrounding vascular structure. But the Dugong presents a 

 marked deviation from the cetaceous structure of the same part, 

 which presents in a transverse section a division of the corpus caver- 

 nosum into two lateral portions, with a middle ligamentous septum, 

 as in the Pachyderms ; the vascular and erectile tissue also bears a 

 greater proportion to the surrounding ligamentous structure than in 

 the true Cetacea. 



'■ In the Dugong the ducts of the vesicula; seminales and testes 

 communicate together before terminating in the urethra. 



" Daubentont has given a figure of the vesiculce seminales in the 

 Foetal Manatee. Steller does not describe the parts of generation 

 in the Stellerus. 



" The testes are abdominal in the Dugong, as in the rest of the Ce- 

 tacea ; but they also have a similar position in the Elephant. 



Osseous System. 



" After the excellent and elaborate descriptions of the osteology of 

 the Dugong, by Cuvier, Riippel, and others, but little remains to be 

 said on this subject. The bones are chiefly remarkable, as in the 

 Manatee, for their dense texture, and the non-development of me- 

 dullary cavities in them : this reptile-like condition of the skeleton 

 is further exemplified in the loose connexion of the bones of the 

 head. The bones are not loaded with oil, as in the Cetacea. All 

 the specimens presented 7 cervical and 19 costal vertebrce, corre- 

 sponding to the 1 9 pairs of ribs ; but the number of the remaining 

 vertehrce exceeded that ascribed to the Dugong by Home and Cu- 

 vier, there being at least 30, making in all 55. Riippell assigns to 



* The separate conditions of these rudimental pelvic bones in the Du- 

 gong is shown in Mr. Clift's figure of the Skeleton of the young Female 

 Dugong. In the true Cetacea the parts analogous to the ischia are alone 

 present: they serve a similar purpose to that in the Dugong. 



\ hoc. ciL, pi. Iviii. fig. 6. 



