358 A. Arnbäck Christie-Linde 



simiae are homologous structures, i. e. is the cartilage which occurs 

 connected with the sickle-shaped cartilago ductus naso-palatini in 

 some animals homologous with the cartilage which occurs quite 

 isolated in others? 



It seems to me that this question may be answered in the 

 affirmative. And for this opinion I find a support partly in the 

 striking agreement between these cartilages in the different animals, 

 partly in the homology of the cartilago palatina mentioned below. 



Apart from the different degrees of development which the car- 

 tilago palatina presents in the different species, the only divergence 

 worth mentioning consists in its relation to the sickle-shaped car- 

 tilago ductus naso-palatini. 



In some species both cartilages are present and are connected 

 with each other. 



In others both cartilages are present, but not connected with 

 each other, the palatal cartilage being quite isolated. 



In others again the sickle-shaped cartilago ductus nasopalatini 

 is absent, and the palatal cartilage is isolated. 



The fact that a fully developed sickle-shaped cartilage is not 

 found in lower mammals e. g. Monotremata, Marsupialia, but is 

 generali} 7 present in higher mammals seems to justify the view that 

 it is to be considered as comparatively recently developed. And 

 most probably it has been developed from the cartilago paraseptalis. 



This opinion is supported by the fact, that, when present, the 

 sickle-shaped cartilage is always connected with the cartilago para- 

 septalis, but not always with the cartilago palatina, e. g. Chirogakus. 



In favour of this view argues also Broom's Observation, that in 

 several Marsupiais there is a process of the paraseptal cartilage, 

 more or less developed, which is the fore-runner of the anterior 

 process which Supports Jacobson's duct in higher mammals. 



The connection between the sickle-shaped and the palatal carti- 

 lages is also probably of late date. The result with regard to the 

 homology of the latter, favours this opinion. 



As mentioned before, I have homologized the palatal cartilage 

 described above with a cartilaginous plate in Echidna, figured and 

 most satisfactorily described by Gaupp 1 in bis great work on the 



1 E. Gaupp, Zur Entwicklungsgeschichte und vergleichenden Morphologie 

 des Schädels von Echidna aculeata var. typica. Denksch. Med. Nat. Ges. Jena. 

 VI. Bd. 2. Teil. 



