PRIMORDIAL CRANIUM OF THE CAT 387 



turbinal region. The latter group is further subdivided by the 

 dorsal end of ethmoturbinal II into two bundles coining, one from 

 the area in front of, the other from the area behind this turbinal 

 process. 



The floor of the nose and Jacohson's cartilage. In cat embryos of 

 the stage modeled, the secondary palate is nearly complete, form- 

 ing a floor for the nasal cavities. The latter are separated from 

 each other by the septum nasi, excepting for a stretch poste- 

 riorly, where the ventral margin of the nasal partition is free 

 from and above the level of the palate. Between the maxillo- 

 turbinal dorsally and the nasal floor is a broad groove of the 

 lateral nasal wall, which extends from before backward to the 

 choanae. This gi'oove, the inferior meatus of adult anatomy, 

 the lower furrow of Legal ('83) or the choanal passage of Fleisch- 

 mann and Beeker ('03), besides differing from the other nasal 

 passages by its origin from the primitive mouth, is specialized 

 through its relation to the naso-lacrimal duct and Jacobson's 

 organ. A striking feature of this ventral part of the cavum nasi 

 is the variabihty among mammals of its cartilaginous walls and 

 floor. This characteristic stands in marked contrast to the usual 

 condition of stabihty of the dorsal part of the ethmoidal skeleton 

 (Spurgat, '96). 



The peculiar characteristics of the nasal floor cartilages in the. 

 cat have been described by several investigators. Our observa- 

 tions must be regarded as confirmatory of Broom's ('96) descrip- 

 tion and of Zuckerkandl's ('08) more recent representation of the 

 paraseptal and related cartilages. Both of these authors found 

 an inner and outer division or process of the nasal floor cartilage 

 (lamina transversalis anterior) and a cartilage related to the 

 nasopalatine duct. 



The significance and homology of these parts of the ethmoidal 

 skeleton have been much discussed. Division of the lamina trans- 

 versaUs anterior, into medial and lateral cartilages (inner and 

 outer parts of the nasal floor cartilages) embracing the nasopala- 

 tine duct, has been observed by Broom ('96) to occur with con- 

 siderable constancy in the mammaUan series. The outer por- 

 tion of the nasal floor cartilage stands lateral to the nasopalatine 



