DB. J. MUBIE ON THE OEGANIZATION OF THE CAAING WHALE. 245 



a careful survey of these structures has been instituted, it is unnecessary to pursue the 

 subject here. I may add, though, that the sacs of Glohiceps are three on either side, the 

 so-called facial division of the naso-frontal being absent. All three genera, therefore, 

 differ from Phocwna in di\ision of the anterior or slipper-shaped premaxillary cavity. 



The next structures whereby homology of parts can be traced are the cartilages. 

 These, compared with the massive head, I may say, are very small, much interwoven 

 with the fibrous and fatty tissues bordering the narial orifice, but nevertheless traceable. 

 Shooting forwards from in front of and between the nasals as a narrow, short and diminu- 

 tive wedge, is a little stump of cartilage, which I take to be the prevomerine ethmoidal 

 or septal cartilage in a very rudimentary condition'. On each side of the above, partly 

 continuous and partly connected by fibrous material, is another, irregular-shaped but 

 somewhat curvilinear and small fibro-cartilaginous isthmus, but which I could not 

 satisfactorily follow out. From position they would accord with the upper lateral 

 cartilages of land Mammalia. Lastly, forward from these and only connected by fibroid 

 tissues (I speak only as far as my dissection permitted me to observe) are the two much 

 larger and transversely oblique masses, visible in the upper opening of the nares, and 

 which are composed of fibro-cartilage fatty substance and mucous membrane. As bearing 

 relationship to the above mentioned, these bodies, to my reading, are homologous with the 

 alar cartilages and their mucous membranous covering, either in wliole or in part. 



Now, if these fibro-cartilaginous masses collectively be rudiments of what I have said, 

 even though I may have mistaken them individually, they afford a clue by which the 

 muscular layers above can be understood aside from their office of dilators and com- 

 pressors of the sacs and narial orifice. Furthermore the muscles and the cartilages 

 furnish data expressive of what the nasal sacs are themselves. Von Baer builds up his 

 homological theory of the Cetacean nasal sacs being the turbinate bones upon one 

 gratuitous assumption, which if unsupported by other evidence than he has given, the 

 whole structural pile of his reasoning falls baseless. I allude to the fact that he 

 considers the thin fibrous induplicated membrane of certain of the rugose sacs an arrested 

 condition of the osseous twisted laminae of the turbinals. In short, he takes for granted 

 membrane replaces bone. As to this being the case, we have not a shadow of evidence. 

 Indeed it is far more reasonable to suppose the ethmoidal turbinates aborted or entirely 

 absent, than that they should be represented by or be transformed into a sacculate 

 membrane of fibro-areolar consistence. It is undoubted that the Cetacea have singularly 

 modified skulls. Some bones are very diminished in size, some wonderfully increased, 

 and others jammed into most abnormal positions, or are unsymmetrical ; but I thinlc it 

 yet lacks positive proof that a membrane completely replaces an entire cranial bone in 

 the adult cranium. 



Luckily for me, Von Baer compares the Porpoise's nasal sacs with those of a calf, 



' As bearing on the subject, consult Dr. Clcland"s well-reasoned paper " On the Relations of the Vomer, 

 15thnioid, and Intermaxillary Bone's," Philos. Trans. 1 863, p. 289, pis. 4 & 5. 



2n2 



