BY R. BROOM. 479 



An examination of the earh^ development of the parts shows 

 that this close connection is not accidental, but that the support- 

 ing bone is developed as a splint to the cartilage. If a mammary 

 fcetus of the common Phalanger {Tricliosnriis viilpecuJa) 18 mm. in 

 length be examined, it will be found that the body of the pre- 

 maxillary is already fairly well ossified. The recurrent cartilages 

 will be seen in section as two plates, slightly diverging below, 

 lying, on either side of the middle line below the base of the 

 cartilaginous nasal septum. About the middle of the inner side 

 of each recurrent cartilage and close to it is a tract of active 

 cells, in the centre of which is a ver}- delicate spicule of bone. 

 This spicule, it must be admitted, is directly connected with the 

 premaxillary, though as the tract of bone-jDroducing cells in con- 

 nection with the recurrent cartilage is practically similar to that 

 which a little posteriorly lies around the base of the septum nasi 

 and gives rise to the vomer, it is highh^ probable that there is a 

 distinct osteogenetic tract in connection with the recurrent 

 cartilage, and that owing to the early development of the pre- 

 maxillary it is prematurely ossified by invasion from that bone. 

 In P'-ranielf's and DriK,,iirus the recurrent cartilage tract is 

 similarly ossiKed by a bony process from the premaxillary. In 

 many of the higher mammals (^^.r/., Erinacenn, Tahtxia) it would 

 appear that the ossification in connection with the recurrent 

 cartilage maintains for some time its independent existence, 

 though uniting later with the premaxillary to form its palatine 

 process. In a few mammals ('?.'/., Ornit]ioi]iynchus and Miniop- 

 terus) the ossification remains as a distinct bone throughout life. 



Prof. Kitchen Parker,"^ who has done more than anyone else 

 to elucidate the development of the skull, does not seem to have 

 arrived at any certain conclusions with regard to the nature of 

 the palatine process of the premaxillar}*. His researches show 

 that he discovered supporting the cartilages of Jacobson a distinct 

 bone which he called the "anterior paired vomer," but it is 

 probable that, as Howes has pointed out, in tr^dng to draw a 



* Loc. cit. 



