120 Trans. Acad. Set. of St. Loui$. 



found in Triton alpestris that the dilator naris muscle takes 

 origin from a similar process, which he calls the anterior end 

 of the Planum terminale. The dorsal part of this bridge in 

 Amblystoma, begins as a process of the Lamina cribrosa, sup- 

 porting the nasolacrimal duct and later coming to limit the 

 Fenestra narina behind. 



The dorsal window of Winslow's fifth stage cannot be 

 explained through my material. There is a continuous carti- 

 laginous roof for the nasal capsule in the 40-45 mm. animal; 

 but whether the dorsal foramen is due to reduction, as I am 

 inclined to think, or is circumscribed by the primary forma- 

 tion of the dorsal process, I cannot say. The dorsal process 

 appears to be a common feature in the nasal capsule of Uro- 

 deles. Bruner ('02) calls it the Cartilago obliqua, a term 

 used by Gaupp also for an oblique process of the nasal cap- 

 sule of Rana. 



Huxley* on theoretical grounds believed that the chondro- 

 cranium was formed phylogenetically by continuous growth 

 and conceived that separate cartilages could have no signifi- 

 cance in the perfection of the continuous-walled brain case. 

 Separate pieces are regarded by the supporters of this theory 

 as the results of reduction of the chondrocranium through the 

 appearance of bones. It was Goette * who first brought for- 

 ward the view that the chondrocranium was made by the 

 fusion of primitively separate elements. 



Regarding the significance of the independent chondrifica- 

 tion of the ethmoidal column in Amblystoma, the claim can 

 hardly be maintained that this piece is morphologically a sep- 

 arate element. Its anlage is in a mass of cells continuous 

 with the incompletely differentiated cartilage of the trabecula. 

 Through the mass, chondrification takes place, beginning in a 

 spot away from the trabecula and then spreading toward it. 

 In Rana, which possesses a much more complete chondro- 

 cranium than Amblystoma, in accordance with its long larval 

 life (Born, Gaupp,) the ethmoidal column develops in direct 

 connection with the basal skeleton. I am therefore inclined 



Bee Qaapp. ('00.) 



